View Full Version : Servicing a SONY DAT machine (Pictorial)
As discussed in a previous thread, I now have two Sony DAT decks that need repair. One DTC 59ES that loads tape but doesn't move it in any fashion and a DTC670 that doesn't even load the tape.
Although I suspect what is wrong with both machines, I haven't yet repaired them or know what exactly the problem is. It will all unfold as I disassemble them, along with pictures and discussion.
I will - hopefully - be able to repair the 59ES as it appears to show the "sluggish" FF/REW syndrome, only so much pronounced that not even PLAY engages properly. The 670 seems an easy repair of a different nature.
As the pictures will show, despite the differences, the transport mechanisms are identical. In fact, I've seen only two different transports so far:
* DTC55ES has what appears to be the oldest (and best IMHO) transport with 3 motors and lots of metal parts.
*DTC 57, 59, 670, 690, Z700 all share the same transport block with the 57 lacking a sensor block and thus having a narrower ribbon cable. But parts are totaly exchangeable.
I also have a PCM R500 that has 4 motors and works like a charm, so I haven't opened it up (yet). I bet this one has a different transport block as well.
The only differences between all the above decks are the loading mechanism. It is nice to see how Sony realized their mistakes in the earlier models and improved upon them with every new model. So if you have any of the above decks with a mechanical glitch, read on.
So, enough talking, let's start the stripping...
Before we are able to reach the transport mechanism, we need to remove the cover.
A word of caution. Unplug the unit from power. Use a bench of adequate size and plenty of light. Don't rush things. If you haven't done this before, don't start now. Disassembly and re-assembly require no power to the unit and it is prefferable that way. Some of the testing require power and unless you totally assemble it for testing, it can be dangerous if you don't know how to work with an audio device. You have been warned!
Before you start, power up the unit, press eject and remove the cassette compartment cover by gently pulling it upward. Then shuttoff the unit and unplug it. If the deck is not responsive or a cassette is jammed inside, don't worry, this can be done manually after opening the unit.
Typically, there are 2 screws to each side for a total of 4. Some decks also have another screw in the back securing the top cover to the back panel. Some others (like the DTC 59ES) have another 4 screws on the top.
These need to be unfastened using a Philips screwdriver. If you are using bits, the PH1 is the best size.
After all this, the unit looks like the one in the attached picture.
Strawman
09-17-2008, 04:11 PM
Looks like an interesting thread. Please heed Sasi's warning about electrical power if you attempt anything similar.
The attached picture is a sidetrack to the discussion.
It shows a close-up of the drum with the foam wheel the designer thought would clean the head. When the tape isn't loaded against the drum, this foam wheel touches the head as the spin stops. It acts as a break and supposedly cleans the drum - if we believe the Sony designation for the part. The foam part is attached to a white lever that moves towards the drum forced by a small spring underneath. When the tape is loaded, the right hand side tape guide (called T1) pushes the lever away from the drum. In some decks I've seen the T1 obscured by the lever and fails to travel to the stop thus loading the tape badly. This results in bad tracking or even tape jamming.
I see this foam part mostly disintegrated. The one shown in the picture is in pristine condition but once we start working with the deck it might break up. We shall see.
It is worthwhile to note that in later models that thing was replaced with a plastic blade that perhaps does a better job but certainly doesn't break up.
I choose to remove that foam and it's assosiated plastic arm. Makes no sense and it probably contaminates the drum rather than cleaning it. If your deck needs cleaning often, it is perhaps because of this.
The transport is encased in the cassette loading mechanism. This mechanism is secured in the deck by 3 or 4 screws, depending on the model.
Earlier (less evolved :D) models used a metal casing for the transport and 3 or 4 screws.
Later models switched to plastic casing (cassette loading mechanism) and 4 screws.
The attached pictures show the 4 screws of this particular model with red arrows. The first picture shows the complete foam wheel and white lever as well.
The cassette loading mechanism is the only major difference between various decks and some discussions on this as we proceed will be relevant to this model only. However, the DTC690 uses exactly the same thing and the DTC -ZE700 a very similar one.
We will discuss small differences with the DTC 670.
The transport assembly is connected to the main PCB by means of 4 cables.
These are shown connected to the PCB in the first picture and also shown numbered in the second picture.
As numbered,
1. The white flat ribbon cable is attached by pressure to the ribbon socket. It transfers control signals, auxiliary motor signals and sensor signals.
2. The small red plug is the capstan motor control.
3. The small white plug isn't actually part of the transport mechanism, but connects to the cassette loading motor directly.
4. The large white socket with lots of shielded cables connects to the drum head. It transfers signal and motor control.
Cables 2, 3 & 4 are braced togther with a plastic clip (barely showing in the top of pic 36650 - sorry for that...). Twist and release it and keep it safe. It's better to clip these cables together when finished for a better look.
Remove the cables from their sockets and unfasten the 4 screws. It's easier to use a magnetic screwdriver so the screws don't fall inside the deck.
When the 4 screws are removed, we can pull the transport out of the deck. This is much easier with the cassette loader in the eject position. If the cassette loader was retracted before that, rotate the large white flywheel to the left of the transport until the mechanism is "ejected".
If there was a tape inside the deck, jammed, causing the mechanism to "refuse" unloading the tape, if you don't really care about the tape, follow the same procedure until the tape is ejected with tape still loaded around the drum or jammed inside the transport. Depending on how the tape is jammed you can gently pull the cassette out and later respool the tape inside the cassette with a thin pencil or screwdriver turning the spools. If you care about the tape, wait until I show you the DTC670 - It has a tape jammed inside.
When finished we can put the deck aside and keep the transport assembly on the bench. It looks like the one in the third picture.
Before we break apart the transport from the cassette loading mechanism, we need to remove one piece from them. If we don't remove it willingly it will come off by itself as we disassemble the block. This is bad as you won't be able to see how it is mounted and how to put it back together.
The part in question is the spring loaded front cover holder. It is mounted at the two edges of the loader assembly (red arrows on the 3rd pic) and spring loaded with a spring so that the cover closes as the cassette is loaded.
Gently pull the spring end that is attached to the front cover and release it from that position. The spring will unload and remain in it's socket.
The cover holder can then be removed by gently pulling the two ends of the loader assembly apart. If you feel uneasy, leave it there and watch how it is released once the screws are unfastened.
There are 4 screws that attach the transport inside the cassette loader. These are shown with arrows in the pics.
There are two screws to the left and another two to the right. The right hand side is easy - the screws are very obvious.
The left hand side is tricky.
The rear screw is only visible and reachable when the cassette holder is fully extended in the eject position. You can do that by manually rotating the large white wheel.
The front screw is visible and accessible on this mechanism - although the pic shows it from an angle.
You will notice that the large flywheel has 3 holes at 120 degree angles. Some models have a larger flywheel that has 6 such holes. In such models the front screw is only accessible through the outer set of holes using a screwdriver through the hole.
In this particular model the screwdriver reaches the screw directly.
I feel inclined to point out that the DTC55 has a large flywheel and no holes! When I was taking it apart I felt lost there as I couldn't reach the screw. I should have totaly disassembled the flywheel and cogs it drives and remove the flywheel to reach that screw.
I decided to "retrofit" the improvement in the mechanism that Sony engineers did in the later models and drill a small hole on the flywheel so I could reach the screw. Saved me a lot of pointless effort. You might find this is destroying the deck, but I fear that unnecessary disassembly is worse.
You can unfasten the screws with the transport block either to each side or in the normal orientation shown in the pictures. Choose what seems easier to you.
In the next few pictures we can see the steps towards the separation as well as the removal of the spring loaded front cover.
The final picture shows the 4 screws that are unique to this assembly. Put these together with the 3-4 screws securing the whole block to the deck and the screws holding the top cover.
The 3rd picture shows the transport separated from the loader. An interesting piece of information can be retrieved there. All DAT transports I've seen so far have a date printed on them. This particular one is dated December 26th, 1992.
If your cassette loader assembly doesn't look like the one in the picture any more and has broken apart in two pieces, read the next post.
The cassette loader is designed so that it comprises of three main segments.
The left part with the motor and pulley,
The middle part, that actually holds the cassette
The right side part that is simply a piece of plastic.
No further disassembly is required here, but the right side part can be split if the right panel is rotated. The picture (tries to) show that the right panel is mounted to the central segment using a rod and a safety clip that once rotated allows the two parts to split. If that happens by accident, remount them as shown.
This is as far as I've reached with this deck today. Taking pictures, processing them and writing this up really takes more time than the actual operation. If you are even slightly experienced with cassette and R2R deck servicing, this is easy. The only hard part is some tools that - obviously - are smaller than what is needed for R2R plus a tool that needs to be custom made.
As it is getting late here (2:00am) I will continue tomorrow with a close up inspection of the transport, some things that can be checked before disassembly and an explanation of the various parts and problems that can be fixed without further disassembly.
Feel free to post questions or comments - I would like this to be interactive - if you have. I am hoping that as we reach the heart of the problem experienced troubleshooters might give some suggestions as to what is causing the sluggish spool performance this particular deck (and a few others) have.
For the next step we need to get better aquainted with the transport mechanism. The attached picture shows the transport from the top.
The two needle micro-sensors shown numbered 1 are for cassette in and rec. inhibit sensing. They travel to the small PCB to the right and from there to the drum control PCB in the back of the transport. Along the way two more sensors are located under that PCB to sense the home position for the bridge that expands the tape load arms (numbered 2 and 3) and the pinch roller (4).
The empty circle in the bottom left corner shows ... nothing. Older transports don't have anything there, just a hole where an extra PCB is mounted in newer models that accomodates an extra set of three pin sensors for media recognition.
How this hole exists before it was decided to mount something there, escapes me. :scratch2: Sony probably knew they had to put something there but left it for later models - perhaps.
The two arms that expand (2 and 3) follow the curved track and end at the two steel stops. Each arm has a pulley and a front "tooth" that needs to go under the stop gap at the end of the travel so that the pulleys are securely in place.
One of the faults in some transports is that one or both of these teeth don't go under the stop. I am guessing this happens when a tape is mangled and is pulled with force. As the cassette reels are secured with clamps when the cassette is ejected, the tape acts as a sling and may pull these fragile levers and bend what is underneath.
This fault can be diagnosed before dismantling . There are other faults that can be diagnosed and fixed without dismantling, but they will be covered after the stripping description as it is easier to understand everything when the whole of the transport is explained.
The two tape loading arms are named S1 for the left hand side one and T1 for the right hand side one. I will refer to them as such further on.
The pinch roller is small as you see and secured in place by means of a plastic circular clip. One of the faults DATs develop is a slippery roller. I have found that the normal rubber rejuvenator for open reel rollers is too strong for them. I have had terrific results by rubbing the roller with a cotton pad dampened with alcohol.
The two tension and load arms and pulleys are the reason why many DAT recorders fail to correctly playback either DAT tapes from others or tapes recorded on the same recorder years ago.
These are adjustable and by adjusting them we ensure correct tracking in almost the same fashion we need to adjust head azimuth on cassette decks and R2R decks.
The attached pictures show the tension arm securely fit at the travel stop, the adjustment slot on the top (with a protrusion in the center that doesn't allow a normal flat screwdriver to be used for adjustments) and the two black screws that secure the stop on the transport plate.
I have seen one case where the black screws were not tightly done and the arm wasn't secure in it's resting place. This resulted in random mis tracking during playback.
The two adjustment pulleys can be rotated and the screw they are mounted upon lifts or drops them, thus altering the azimuth.
Don't touch them for now and don't worry that dismantling will ruin the alignment. The alignment is ensured by the fact that the tooth in the front of the arm locks inside the stop.
To the left edge of the transport (as seen in the picture) there is a small cross screw. This screw controls back tension. When fully in, back tension is at it's max. When out, back tension is at it's minimum.
Forward tension / torgue is adjusted electrically (will talk about it during adjustments).
Make sure the screw is there.
At the front right edge of the transport you can see a set of gears, white and black. From the front you can touch the black one.
These gears move the bridge inside the transport from left to right which extends and retracts S1 & T1. It also moves the pinch roller in contact with the capstan.
You should be able to rotate the black gear with a single finger and see the arms slowly extend and retract as you rotate the gear in oposite directions.
If you feel there is too much friction and you cannot easily rotate the gear, it means there is something wrong in there. It can be either dirt, or someone lubricated the transport with the wrong material, or one of the arms is bent, or someone tried to fix the transport and left stray cables that inhibt the arms from moving.
When the arms are fully extended, rotate the black gear some more. It should start to move the pinch roller further until it contacts the capstan. When this happens, check to see that the pinch roller is really in contact with the pinch roller and that it doesn't slip. Try to rotate the roller and if it does then it is either not in contact or is slippery. Check visually for contact.
nakmandan
09-18-2008, 01:01 PM
Excellent work SaSi! Very detailed pictures. I look forward to reading more as you post.
I have been lucky so far in that my DTC-75ES has always and continues to work well, even after 17 years. Never had it serviced or opened. I'm the only owner it's ever had, got it direct from a Sony employee. I know my luck can't continue for much longer however, that's why I'm so interested in this thread. I don't recall ever seeing a comprehensive DAT maintenance thread anywhere else. A true trailblazer you are my friend!
The only problem I've ever had with my machine is that 3 or 4 (out of more than 100) tapes I made 16-17 years ago have a few digital dropouts in them. Not sure if it's the tape or the machine starting to go out of alignment. I suspect it's the tape because all of my other tapes, even a few recorded on a different machine (an A&D D-930), continue to play well.
niklasthedol
09-18-2008, 01:10 PM
Very Cool thread SaSi.
I'm not into DAT renovating myself and not realy much into DAT at all.
But the way you contribute is great.
"dolph"
rockin1150
09-18-2008, 01:19 PM
Nice! I always wanted to see how those machines looked inside:thmbsp:
In the bottom of transport the only thing visible is the spooling motor and the spooling gear connected with a geared belt.
This belt needs to be hard and loose. In some models, the second screw mounting the spooling motor is adjustable. Don't be tempted to adjust so that the belt is fastened. Nothing will work then. The belt needs to be loose, just enough so that it doesn't disengage from the gear.
The idea behind this will become obvious as the transport is opened up.
Before doing that, one test that needs to be done is to manualy rotate the spooling gear clockwise and counter clockwise (parts of a rotation are enough).
One direction should give a small rotation on the left spool and the oposite direction should give a small rotation on the right spool.
On the transport at hand, the take up reel doesn't rotate but the left one does. That explains why tape can be loaded and safely unloaded but not played or FF/REW. We are getting closer to facing the problem.
Thanks guys. I stopped todays session for a quick nap and saw the postings after I continued. It was getting a little lonely in here...
@Nakmandan, the DAT tapes are very very sensitive to curling and bents. Even the slightest bending will cause audible distortion sounding like a dropout or digital noise. It is because the tape at the bend or fold looses contact with the head and when it passes through the S1 T1 guides it changes azimuth.
In all fairness, I knew nothing about DAT some 4 months or so ago. You can look up a question I posted about tapes not reproduced properly on one machine and good on another. I confess I wasn't convinced by the answers so I just had to dig more.
The attached picture shows an anomaly on the back side PCB. This red color shouldn't be there. It's not my blood or something. I have no idea what it is or if it affects anything.
I am spotting this as during troubleshooting one needs to be alert for minor things that act as telltales for problems.
On another deck all the screws were loose. What does this suggest? That someone had worked on the unit, forcing me to look out for iregularities, misplaced parts or badly repaired faults causing other problems.
The transport consists of three main blocks. The top transport plate that is visible when looking at the drum head, the bottom transport mechanism that is screwed on the plate from below and the drum control board that is fastened atop that.
We work from the back so we need to rest the mechanism face down (or better drum down). If you are afraid to rest the drum on the bench I feel for you, I've had the same feeling myself when doing it for the first time.
As long as excessive force isn't applied all is ok. Just make sure the work surface is clean of dust, metal particles and liquids. No coffee allowed here.
We start by removing the drum control plate. On this particular model it is easier than newer ones as the left hand side media detect sensors are missing and so is the extra cable that comes with them. You will have a chance to see how this complicates things with the 670 that follows.
The short story is we need to undo the 3 screws, one at the center of the PCB and two more fastening it in the back directly on the metal chasis of the transport. We have two different types of screws here.
Once the screws are removed, we need to slide the PCB backwards so that the 4 cables traversing the board don't get in the way, raise those cables and bring them under the PCB and while raising the PCB for the first time since Sony assembled it, untie the cables inside from the two metal guards.
Sounds complicated but take a look at the pictures and it will become clear.
Picture 1 shows the PCB in place but screws removed.
Picture 2 shows the PCB slightly shifted to the back and the cables disengaged from it.
Picture 3 shows a peek of the cables underneath as they are settled.
Picture 4 shows the PCB laid aside leaving ample access to the transport mechanism itself.
nakmandan
09-18-2008, 02:03 PM
The attached picture shows an anomaly on the back side PCB. This red color shouldn't be there. It's not my blood or something. I have no idea what it is or if it affects anything.
I am spotting this as during troubleshooting one needs to be alert for minor things that act as telltales for problems.
On another deck all the screws were loose. What does this suggest? That someone had worked on the unit, forcing me to look out for iregularities, misplaced parts or badly repaired faults causing other problems.
That stuff actually looks like the glue or epoxy whatever used to hold the SMD components in the foreground of the picture. Careless assembly? Does it come off?
Now that the PCB is removed, we can have a closer look at the transport from the bottom.
The spooling motor, belt and spooling gear are now clearly visible. We can test the tightness of the belt and can also repeat the same test as before for the spooling gear. We can see the striped bottoms of the cassette reels turning or not as we rotate the gear. These stripes form a feedback to the magnetic sensors that are mounted on the drum control PCB. They sense if the reels rotate when they should and stop the unit when they sense reels don't move when they should. For this reason it is impossible to test the transport in it's current state - although that would be desirable.
At the left edge of the black plastic area the motor controlling tension arms and pinch roller is seen.
Next to it we have the capstan motor. It's the one with the designation U-17B. It is a miniature of the motor's I've seen on my Revox B710 and ultra miniature of the direct drive motor on the Revox TTs, so you understand this motor gained some respect from me :D. What didn't help gain any respect is the spooling mechanism that is the source of all the troubles.
To the right of the capstan motor we can see the bottom of the drum motor in the shade.
So, ignoring the mechanised cassette loading and the moving drum, we have a 3 motor DAT transport here. So now you know, 3 motor DAT transports are the cheap, low end versions. The better versions are the 4 motor transports that lose the gears and place one motor under each spool.
We have more work to do now to split the transport in two parts. There are 4 screws to undo. They are anotated with arrows in the pictures. 4 black long screws and 1 brass screw securing the underside of the transport at the front edge of the main chasis.
I recommend that you undo the 4 black screws first and leave the brass screw last.
Once all 4 screws are removed we need to gently lift the undercarriage. And by gently I mean slowly and carefully watching for things that might be thrown out. :D OK, this won't happen but there are a couple of spring loaded parts inside and a mishap with a tape might have caused them to jam. In some cases a simple removal of the undercarriage, inspection and reassembly is all that is needed.
When I raised the undercarriage I felt resistance at first - this is why I am giving the advice on going gently. I knew I was not doing something wrong so I continued gently and felt a small snap and the resistance was gone.
I did not see what was jammed but I suspect it has to do with the tension arms as I felt them hard to move by hand and they are spring loaded.
That stuff actually looks like the glue or epoxy whatever used to hold the SMD components in the foreground of the picture. Careless assembly? Does it come off?
Haven't tried. And as I see it all SMD components have a red dot under them... Could this have to do with the fact that the unit was assembled around Christmas?:scratch2:
We are now inside the transport, having visual access to all the parts. Further dismantling is still possible and sometimes required, especially if a part needs replacement.
The attached picture shows everything together: The main transport chasis to the left laying on it's top, the undercarriage to the right and the Drum drive board to the back. On this picture the magnetic motion sensors for the reels are more clearly visible as the white components with the black part in their center.
We now need to take a break in breaking things apart and familiarize ourselves with what we see. And I need to take a break as I take a few more pictures.
The attached pictures show a general overview of the assembly and some close up details of parts of major interest.
We have already seen the capstan before and now we can see it in it's full glory unobscured by other parts. The two screws visible on the capstan motor's PCB are of no interest The capstan motor is mounted on the chasis by means of 3 ultra miniature screws facing the top plate. If we need to remove the capstan motor we need to have a set of jeweler's screwdrivers of high quality.
The lower part of the picture is dominated by the white plastic part, what I call "the bridge". You may come up with a better name - English isn't my native language.
This part has a toothed edge to the left. The set of white and black gears we tried to move by hand before dismantling engage here in a rack and pinion fashion to move the part left and right.
As we see it depicted here the bridge is towards it's right end of travel but not quite so. Therefore we can see the tape tension arms slightly extracted upwards towards the drum.
When the bridge travels to the left of the picture the arms extend fully. The bridge needs to move freely from left to right and as we try to move it by hand we must not feel any jamming point.
The bridge is secured in place by means of 4 black and flat metal pins. One can be seen at 11 o'clock of the right spool hole, one at 4 o'clock of the same hole, and two more towards the upper left and lower left of the left hole.
These pins can be pulled and removed if we need to remove the bridge but removing the bridge involves removing the capstan motor first.
Unfortunatelly, this doesn't appear to be necessary for this unit.
Towards the upper end of the bridge and to the right half we can see another set of racks. There we have the pinions of the tension arms. As the bridge slides the pinions rotate and the two part arms unfold following the slotted trace on the chasis to extend.
One of the faults I mentioned in before is having a tape mangled inside the deck and by pulling it bending these arms. Obviously it is the outer, steel part that is bent. If this happens the tension pulleys get raised and then the front tooth they have doesn't engage in the stop properly.
If we have such a case, we don't really need to dismantle the arms. Just a gentle application of pressure with the rubber end of a pencil in the middle of the steel arm starts to correct the bend. As always it is better to do that in small steps, each one bringing the arm closer to flatness.
You might have noticed that there are two springs inside the bridge close to the rack&pinion mount of the arms. This might not show clearly in the pictures but the springs are attached on the bridge at one end and to a sliding plastic part at the other end. The sliding plastic part contains the rack. The spring forces the rack to move with the bridge rotating the pinion and extending the arm. But, if the arm is jammed for whatever reason, the spring extends and the arm stops extending. The other arm - if unblocked - continues to extend. One of the deck's I've seen had the whole assembly for one arm dislocated and the rack was disengaged from the bridge. This is one case when the bridge needs to be removed - and so is the capstan motor.
The two arm pinions are secured in place by two small round clips. One should be black and the other white. At least that is what I've seen so far. But not on this deck.
There are a lot of such clips - on the undercarriage - and one problem with them is they tend to go and the part that is secured - especially the arms - gets further dislocated. If this happens and the owner of the deck continues to try to load and eject tapes it is very likely that the steel part of the arm will jam and bend. Have seen this - haven't seen anything break yet.
The undercarriage (again my own invented term) houses the two auxiliary motors, the reduction gears for the bridge slider, the reels and reel direction selector as well as two solenoids.
Again the first picture shows an overview and the remaining pictures show detailed closeups of the "usual suspect" parts.
To the top left we see the spool motor. To the right we have the bridge motor attached to the 4 reduction gears (2 black - 2 white). Then we have the two spool shafts with gears and between them we have the direction selection gear driven by the belt.
The black solenoid controls breaks and back tension and the black one appears to break the bridges shifting and release the spools and vice - versa.
We now have reached the heart of my problem... Let's describe the spool function in detail.
The spool motor rotates either clockwise or counter clockwise.
When rotating counter clockwise and the belt transfers the rotation to the spool direction shaft (between the reel shafts), it ROTATES that shaft to the same direction bringing the center gear in contact with the appropriate reel shaft. It then enganges that shaft rotating it to the correct direction.
So, when the motor rotates counter clockwise the center gear slides to the left and turns the left spool counter clockwise.
When the motor rotates clockwise, the center gear slides to the right and rotates the right gear clockwise.
In order for that to happen, the yellow solenoid needs to release the breaks. When the tape stops the breaks are engaged.
The breaks are the two black arms sitting on top of the spool gears as we view the picture. When the solenoid engages (pulls the rod inside) the black arms push against the spool gears. I don't know if it is clear in the picture, but there are friction pads where the break arms touch the gears. On one machine the sluggish FF/REW was caused by glue bleeding from the pads and causing additional friction with the shafts.
By removing the arms and thorougly cleaning them the problem was eliminated. I replaced that pads with a tiny piece of friction lining for the Revox breaks. It works fine.
Some comments on the close ups:
The first close up shows the gears. It is visible there that there is dust and debris accumulated between them. It also feels clogged. They need to be removed and washed.
The third picture shows a detailed view of the spool direction selector. The steel shaft houses the gear accepting rotation from the belt and the lever that houses the crazy gear that attaches itself to either of the spools. In the picture it is shown attached to the take up spool.
One mystery is why decks that show sluggish FF/REW/PLAY unload the tape (by rewinding the slack tape back to the supply reel) perfectly ok. I am suspecting that such a behaviour shows that the gears engage ok and shafts as well but only if the solenoids allow them to do so.
The fourth picture shows a close up of one of the many round plastic clips securing the various parts on shafts. If when you shake the deck you feel small things rattle inside, open the deck carefully and look for the offender. It might be one of those clips. Don't loose them - I haven't been able to figure out a suitable replacement myself. I've almost used all the clips from a donor machine that was shot.
The last picture shows the yellow solenoid and the back tension adjustment screw. Actually the transport chasis has room for two such screws but all decks I've seen and the service manuals only show one. Strange. This screw is one of the last things to adjust. Remember the holes I was mentioning on the cassette loading mechanism white flywheel? (OK you can look back at that posting). They are there to allow setting the back tension screw with the whole thing assembled. Some models that house the transport to the far left even have a hole in the base chasis to allow a (long) screwdriver to pass through...
vincei
09-18-2008, 09:43 PM
I had a sluggish DTC-59ES that I sold off in early 2000. I hear that there were some problems with that model of transport. So far my 75ES is ok. I also had a A7 that has the sluggish transport too. Good luck, you have more patience than me. :music:
Tinman
09-18-2008, 09:46 PM
Well, SaSi should really enjoy fixing mini DV camcorder mechs. :thmbsp:
I had a sluggish DTC-59ES that I sold off in early 2000. I hear that there were some problems with that model of transport. So far my 75ES is ok. I also had a A7 that has the sluggish transport too. Good luck, you have more patience than me. :music:
The same kind of problem is found on several of the mechanisms used in DTC57, DTC 59, DTC670, DTC690 and DTC ZE700. All these decks use the same transport with minor differences on the first two models. There must be other models out there sharing the same transport, just haven't seen them all.
I've seen recent (2002) builds of the transport suffer and old (1994) versions work flawlessly. I'm thinking of taking two such units and exchange parts to see what is the offending component.
I am suspecting the pressure pads (has been proven to be the cause in some cases) a weak spooling motor, a weak release solenoid (the black one) or gummified lubricant. It could also be a combination or all of the above depending on the condition of the unit. One was totaly cured by soaking it in hot water with detergent (just the undercarriage), rinse with de-ionized water and then baking it at 40oC to dry.
I do have patience in fixing this. My wife likes to solve crosswords I find that a waste of time. Others might find what I do a waste of time. But after working with computers and software for 20 years, the revival of this new hobby - combined with now being able to fix things rather than brake them worse 0 - is refreshing...
nakmandan
09-19-2008, 09:24 AM
I do have patience in fixing this. My wife likes to solve crosswords I find that a waste of time. Others might find what I do a waste of time. But after working with computers and software for 20 years, the revival of this new hobby - combined with now being able to fix things rather than brake them worse 0 - is refreshing...
I'm right there with you SaSi. The fixing part of this hobby just started for me less than three years ago. I'm self taught.
My wife likes to do needlepoint and cross stich. These hobbies between the two of us gives us enough space that we don't drive each other crazy after 13 years of marriage.:rant::smilemad::twak:
She used to give me grief over buying up all this equipment but now realizes it's my thing, the cost doesn't add up to what she spends on herself with trips to see her family and at least I'm not out rabble rousing and boozing. Not that I'm inclined to do that anyway, but it's a point in favor of my argument.:D
I get tremendous satisfaction bringing something back to life that has been written off. Especially when I have to improvise due to parts availability.:rockon:
Back to the unit now. I removed the 4 reduction gears. The way to do it is unscrew the small brass screw that secures the top black gear. Then remove them one by one. In order to remember how to put them back together, remember this. They go (from motor to the end) white-black-white-black (and the last one get's screwed in).
The double gears fit last and the simpler gears go in first. It's easy, especially having the pictures reminding us how they fit.
Removing the first gear (the one with the screw) was hard. Whatever lubricant was there initially was gummified and had turned into sticky glue. Gentle but firm rotations and some pulling solved it.
The other three gears were easier to remove but were certainly less free to rotate than I usualy see these.
I saved the screw and soaked the gears in water with detergent overnight. As the same time I cleaned the shafts with qtips and alcohol several times until I could feel them clean.
The rest of the transport's undercarriage I cleaned by spraying with alcohol using a focused vaporiser. I let the alcohol drip off to the sink.
All that happened Thursday night. I went back to to work with the unit this morning.
I don't know if anyone wants the assembly process documented. It is exactly the opposite of disassembly. I don't want the thread tediously long so for now I skip pictures of the reassembly process - unless anyone asks for them.
Now, there are some good news and some bad news.
The good news is that the clogging of those gears was responsible for inhibiting the pinch roller touch the capstan. Remember, those gears move the tape load arms and a bit further it enganges the pinch roller.
The transport operates like a charm. Excellent FF/REW, stable and without moaning and also playback. Audio is reproduced and all seems to work.
The bad news is that the transport exhibits a new (for me) kind of problem. I need YOUR help and suggestions here.
The pinch roller seems to pull the tape up or down against the capstan and eventually the tape is disengaged from the capstan. I have seen this problem in the past with seriously deformed and hard pinch rollers on cassette decks.
I don't have a new pinch roller but I do have 3 spare ones from transports sitting on the shelf with sluggish FF/REW but good play capability. I tried to exchange all of them and use them in the transport under test but the same problem persists. It looks like some pinch rollers will pull the tape up and others will pull the tape down.
This appears to be something to do with the capstan and pinch roller not being totaly parallel to each other. It could be caused by a deformed pinch roller but at least 2 of those I tried are ok (not only visually but after testing on decks).
I will be taking close up pictures of the test and the transport under test and post them later on in the day. For now I welcome any possible suggestions.
vincei
09-20-2008, 03:08 AM
My DTC-59ES did "crinkle" the tape by having the tape slide down the capstan. It only seemed to be a problem at the beginning of the tape and not all tapes had this problem. I don't have any solution, but for some reason Sony seemed to have this problem with thier DAT and Cassette transports as I had a TC-K679ES cassette deck do this too. I seem to recall the pinch roller was "bowed" outward in the center and thought that was strange.
Henk50
09-20-2008, 04:02 AM
The pinch roller seems to pull the tape up or down against the capstan and eventually the tape is disengaged from the capstan. I have seen this problem in the past with seriously deformed and hard pinch rollers on cassette decks.
Well I have make in the past a new 'pinch-roller' for an old cassette-deck.
I have a couple dozen rubber's as spare part for some water-tap's.
The nearby look-a-like rubber I could used for the pinch roller.
So I did it cost me a half-day before it has the dimensions of the old rubber,
I drilled and grinding the rubber for several hours,
before it has the right dimensions, and when it was parallel to the capstan.
It did the job.
So I do it also for my Sony DAT (R300) if this occur in the future.
As I see it, you are suspecting the pinch roller. That's exactly what I did and that's why I replaced it with others, known good ones.
I am attaching two pictures of the pinch roller that causes most of the trouble.
In the second picture it becomes more obvious that the friction surface isn't flat but convex. This is actually the opposite of what vincei described and I've seen some other pinch rollers having a curved surface. Mainly small ones but also the ones on the Technics RS-15xx closed loop.
I am guessing that the curved surface allows for it to become flat once pressure is applied and this DAT transport certainly applies much pressure. The pinch roller is enganged by means of a motor rotating at high speed and the 4 reduction gears converting rpm into torgue. I can see the gears slowly turning as the roller engages, ensuring an even firmer contact.
I am now guessing again that a convex surface on the roller makes pressure at the central part uneven and uncertain. This might be the reason that the tape is grabbed by whatever part of the roller makes better contact.
In order to prove or disprove that, I reversed the roller (it is symetrical). Now the tape curled under the roller but not as often as before. And yes, it is more likely (almost certain) to happen at the beginning of the tape.
One more thing is that I tend to use scrap tapes with these tests. They have been mangled once or twice at some point of the tape and have several other problems, basicaly not good tape.
Fast forwarding (yes the deck can do that now) to the middle of the tape, things get better.
Another problem with this transport is that it doesn't provide good back tension. In fact I wonder if it does back tension at all. I see the tape slacking at the rollers and the characteristic reflection from the tape surface changing as it travels showing that the tape isn't pulled back constantly.
This is a different type of problem (actually a calibration matter) and I'l cover it later, for now we need to establish operation where a good tape doesn't get mangled.
I will try grinding the roller a bit, take pictures and report back.
Tinman
09-20-2008, 10:38 AM
SaSi, on the pinch roller problem, check the tape tension. Too loose and it will ride up or down. Check the takeup clutch and the backtension band. Most likely the backtension.
EDIT: Just noticed that you don't have backtension. That's your problem.
Unfortunately I cannot see if the mechanism is using a brake band or clutch to tension the tape. If it's a clutch, make sure you put the reel tables back in the same order. Usually the clutch is in the reel table, and locked by a cog.
Well, you'll figure it out when you see it.
junkaudio
09-20-2008, 01:16 PM
i´am happy with my sony dtc 1000 es dat 4 direct drive motors no problems :banana: 16 years in use
SaSi, on the pinch roller problem, check the tape tension. Too loose and it will ride up or down. Check the takeup clutch and the backtension band. Most likely the backtension.
EDIT: Just noticed that you don't have backtension. That's your problem.
Unfortunately I cannot see if the mechanism is using a brake band or clutch to tension the tape. If it's a clutch, make sure you put the reel tables back in the same order. Usually the clutch is in the reel table, and locked by a cog.
Well, you'll figure it out when you see it.
Well, I did: When I disassembled the undercarriage, I removed a tension spring connecting the two white arms that press against the spools. I didn't put that back on. The result is that there was no friction against the spools, solving the sluggish FF/REW no PLAY but as there was no tension hell broke loose with the pinch roller. I saw that as soon as I opened up the unit again.
Conclusion: Don't work on fixing things when you are tired and sleepy. You will make silly mistakes you won't even suspect you did. I know I did...
So we are back with perfect tension, all my pinch rollers are running well but running sluggish for reasons unknown. At least I have it where I want it. Causing the problem I want to solve.
Tinman
09-20-2008, 04:58 PM
Did you take the capstan motor apart, clean, and oil it? This was already a problem with 8mm decks.
Did you take the capstan motor apart, clean, and oil it? This was already a problem with 8mm decks.
No, but I think this one calls for a total stripdown. It's a good opprtunity to document the whole thing.
The capstan seems to function OK, but I am not sure that there is no oil that leaked and contaminated the capstan's shaft.
In any case, I removed the capstan for cleaning. Although it is not necessary to remove the shaft itself, it helps both document and handle the two white washers.
To remove the capstan the 3 small cross screws need to be undone from the top of the transport. These are shown in the first picture.
The rotor is secured in the motor assembly by magnetic force. To further reduce the effects of stray cables inside the assembled transport it is shielded with a clear plastic cover. One screw secures it.
In the 5th and sixth pictures, the two white washers are clearly visible. They are there to protect the ends of the shaft from tape particles that could otherwise attach the friction points.
To remove the rotor only a gentle pull is needed. Also care is required so that the two white washers don't jump and get lost.
The two last pictures show the rotor and windings of the capstan motor.
I cleaned and reassembled the rotor / capstan shaft but it didn't make any difference (negtive or positive).
Judging by the behavior I see, I would guess the problem is combined gummed up lubricant in various places and a weak (?) solenoid (the one that disengages the breaks).
Tinman
09-21-2008, 09:21 AM
The capstans tend to drag. We had to clean and oil them when I fixed camcorders. Typical on Sony capstans. Oh, I could tell you stories....
OK, I compared the transport exhibiting the FF/REW/PLAY sluggish performance with one that operates fine and was able to track down the fault.
I need to refer you to a previous picture (http://www.audiokarma.org/forums/attachment.php?attachmentid=109138&stc=1&thumb=1&d=1221771576). We need to discuss the two solenoids.
The yellow one (horizontal orientation in the pic) is responsible for back tension. The black one is responsible for the breaks.
The difference that I noticed between the two transports in operation is that the "good" one will plunge the solenoid and keep it plunged while the tape is moving. As soon as transport is stopped the solenoid is released and the breaks engange.
The "faulty" transport seems to plunge the solenid at all the correct times, but the solenid doesn't keep position but instead is released. This results in the breaks being enganged while the tape should move. Not really easy to do that.
Now that the reason for that has been found, I need to find the reason why the plunger doesn't remain in place. It is obvious that for that to happen a steady current flow must be ensured through the plunger. It appears that is not the case.
I am studying the service manual to see what could be wrong. There is a large TO-220 transistor showin in the service manual as driving the plunger and I wonder what mode of failure can cause the transistor to deliver pulses but not keep them alive. There is also a buffer IC there used in several functions related with motors and solenoids. That could be also suspect.
I am now thinking of putting two decks on the bench. One that operates flawlessly and another with a problem. The fault appears not certain to be isolated on the transport mechanism. So, an exchange of transports between a faulty and a working deck appears tempting.
vincei
09-21-2008, 12:50 PM
Interesting, I wish you were around 10 years ago! I sold my MINT in box, low hours 59ES for next to nothing because of the sluggish transport. :( I seem to recall a service bulletin for these transports. In fact I recall trying to order a new complete transport and got a look like I was nuts from the guy at the counter. :D
Interesting, I wish you were around 10 years ago! I sold my MINT in box, low hours 59ES for next to nothing because of the sluggish transport. :( I seem to recall a service bulletin for these transports. In fact I recall trying to order a new complete transport and got a look like I was nuts from the guy at the counter. :D
Sorry to hear that vincei. But it is interesting. Low hours mint condition. The sluggish transport problem doesn't appear to be tied to 1000s of hours of operation or years of idling in storage then. Therefore it CAN be an electronic part failure.
Did you use 60 and 120 minute audio tapes only or did you also use DDS 90m and 120m tapes giving 3h and 4h play time?
The reason I'm asking is that these tapes have almost double the weight of tape compared to the normal audio tapes and that could cause marginal operation due to the higher load.
Torgue in the DAT drives are in the order of single digit g/cm for the SONY transports. Direct drive transports (like Panasonic and JVC) can have 50-150g/cm torgue but the Sony ones are marginal for heavyweight tapes - hence the problem with moaning FF/REW and failure to rewind 120m tapes even in perfectly running machines.
vincei
09-21-2008, 01:27 PM
I always used audio DATS from Sony or Maxell. I used 60, 90 and 120 minute tapes, all had the same problem. I had only put about 200 hrs on the unit at most, maybe lack of use was a problem. I bought it in the fall of 1992 and it started having the problem about 1998. I seem to recall looking at the transport at the time and also suspecting the solenoid wasn't releasing the brakes enough. I also bought a used A7 DAT that had a completly frozen takeup reel.
I always used audio DATS from Sony or Maxell. I used 60, 90 and 120 minute tapes, all had the same problem. I had only put about 200 hrs on the unit at most, maybe lack of use was a problem. I bought it in the fall of 1992 and it started having the problem about 1998. I seem to recall looking at the transport at the time and also suspecting the solenoid wasn't releasing the brakes enough. I also bought a used A7 DAT that had a completly frozen takeup reel.
Lack of use should be the reason for failure on heavyweight heavily lubricated and greased machines. Although I have seen some grease gumming in sony DAT transports (1 out of 15 units), I think that these sparcely lubricated machines don't fail if not used (save for some atmospheric contamination on the head drum that might render the unit mute (until cleaned).
At the title says:
I brought up from the basement two different units, reason being I had to compare two identical machines, one having the fault and one not. And the two easiest to access machines were 2 DTC ZE700 units. Actually one, as I already had a problem unit on the bench...
I verified that the transport on the "good" machine operated flawlessly and then I transplanted it to the host deck that originally housed the "faulty" mechanism. It doesn't operate any more. Not even play. BUT it DOES rewind the tape back in the supply reel when eject is pressed (like all "faulty" transports do).
I then put the both transports back to the host deck that originally hosted the "good" transport. The one originally there of course operates flawlessly. The second one is also working flawlessly.
Therefore:
The sluggish FF/REW and sometimes PLAY fault is NOT a fault of the transport but a fault in the main PCB that hosts the control electronics for motors and solenoids. Most likely the fault is lack of steady signal to the break solenoid. The breaks need to be released during tape transport and the fault is failure to release the brakes.
Now some bad news:
Firstly, my attempts to fix the problem transport included heavy cleaning and removal of the slightly sticky tension pads. The result is that the "previously-thought-of-faulty" transport operates freely now, but a tad too freely - no back tension. The result is that FF/REW is free but a bit jerky and lack of back tension causes the tape to curl off the pinch roller.
Secondly, as I considered how to work on the main PCB I realized removal of that PCB is a major task. Not difficult or risky of braking things but big time tedious.
Thankfully, I have a set of DTC ZE700 electronics in a box removed from an enclosure that was shot. The electronics operate ok and I hope the PCB has the same problem so I can work on that and identify the fault.
A hint: Touching the power transistor on the faulty PCB I feel it hot and I also feel it rather loose on it's leads. Like something is unsoldered or broken underneath. On the good machine, several cycles of FF/REW don't seem to increase temperature to a level I can feel it by touching.
Now that the fault is isolated on the main PCB I have to work towards fixing the "faulty" transports using the good deck as a testing unit. My plan is to clean and lubricate the transports, replace loose and missing tension pads and document that procedure. When this is over, I will work on the PCB faults that cause the transport failure.
The reason is: All these units share a virtually identical transport but differ in the electronics. I also feel more comfortable with the mechanical aspects rather than the electronic ones (for now). Therefore as soon as transport issues are eliminated and described, we can delve into the unknown and troubleshoot the circuits.
Tinman
09-21-2008, 02:21 PM
Very interesting....
Cold solder connections were another common problem, but hot transistors... hmmm.
I'd resolder it first, just to see. Then replace it. That's pretty interesting with the solenoid.
(Makes notes...)
I'd resolder it first, just to see. Then replace it. That's pretty interesting with the solenoid.
Will most certainly try resoldering first.
Well, I brought out the electronics parts from that shot ZE700 and laid them on the bench.
The good news is that both transports (the verified one and the previously suspect one) operate in the same way they did with the good host.
The bad news is that I cannot troubleshoot this PCB :sigh: That means that I need to remove the PCB from the other deck and use that instead.
That's a considerable amount of work and pictures and for now I only took a few pictures of the "workbench" version of the deck. More will come tomorrow evening.
For those who might have lost this, I've temporarily stopped working on the DTC-59ES as I had to compare working and non working transports, which later moved to comparing working and non working PCBs - as the transports were proven inoccent.
I have quite a few DAT units around, but unfortunatelly only one DTC59ES, therefore troubleshooting that fault needs to switch into troubleshooting DTC ZE700s of which I have plenty.
As a sidenote, the ZE700 is a much newer deck which adds the SBM circuit (Super Bit Mapping). Apart from that, it appears to be more or less a DTC690, which appears to be a cut down version of the DTC59ES.
The circuitry in all these machines are quite similar, even the designation of certain parts is the same. I've compared the schematics of the 59 and the ZE700 and the spool motor / plunger driver circuits are quite similar. Therefore, I am hoping that solving the problem on the ZE700 will point directly to the offender on the DTC59 as well.
I hope the above cleared things rather than confusing the issue even further.
Tinman
09-21-2008, 05:00 PM
Uhhhh...........:scratch2:
Naaa, just kidding. :D
I removed a faulty PCB from a deck. The pictures show the particular unit and the red circles show where plastic retainers need to be twisted with pliers. In total 8 white retainers are to be released.
In addition to the retainers, two plugs from the transformer and another two from the headphone amp and line in volume control need to be disconnected.
Finally, 4 brass screws need to be undone in the back, close to the analog and digital inputs and outputs.
Removal of the PCB isn't as hard as I recalled for this deck. It was hard on the particular one I worked on as that was crushed and deformed and I had to work around so that the PCB wouldn't break. Strangely that PCB not only survived but also performed well in the "sluggish transport" department.
The next few pictures show the main PCB from the underside, mainly to show a peek on the ICs. This particular deck (DTC-ZE700) has the ICs surface mounted at the bottom.
By the number of jumpers on the board, I assume it is a single layer board. Therefore the SMDs need to go under. So much about high-end and expensive...
The second picture shows a general view of the motor and solenoid control area from below. The third picture is a close up of Q451, the TO220 transistor I felt being rather loose. The solder is broken there. Fortunatelly the tracks are intact.
The first thing I tried was to resolder that particular transistor (although it is not the one responsible for driving the offending solenoid).
As I worked on resoldering that and a few other joints I saw as suspect, I was in for a big surprise. Quite a few of the soldering pads, when warmed by the soldering iron, lose their solder. The last picture attached shows Q459 and the middle lead shows how solder is going away (onto the soldering iron).
It appears that the PCB has very little (I dare say inadequte) solder on the tracks.
I re-soldered all the passive components near the motor and solenoid control area and also the transistors.
As soon as this was finished, I reconnected that faulty PCB back to the testbed version of a DAT and tried 3 mechanisms I have handy. None of them operated properly and with all of them the same problem. The brake solenoid doesn't release.
I attach a block diagram of the solenoid driver and a shot of the actual circuit driving it. It is driven by Q481.
The service manual diagrams are useful as they provide reference voltages to check across the circuit. So I ventured to probe the referenced voltages. More or less the readings are what the circuit describes.
I measured 3.54 at the base and 4.65 at the collector while the emmiter voltage was just a bit lower than 2.8V. Compared with the voltages measured on a good-working board, these values are within the measurement error.
By measurement error I mean that these values are there for 1-2 seconds after PLAY or FF/REW is pressed. Soon after that the deck decides it can't move the tape and aborts.
I was not surprised to measure these figures. I was surprised to see these values last that long while the solenoid just fires and retracts. I was expecting to barely measure any pulses as I was thinking that for some reason, instead of providing a steady current, the circuit was merely producing a brief pulse.
I did measurements both in peak hold mode and in RMS mode. The measurements don't differ.
Now, I am really stuck. I can't figure out why this is happening. The circuit appears to be healthy, all solenoids measure approximately the same resistance (19-20Ohm), yet some PCBs are able to hold the solenoids in while others can't (the same solenoids). :scratch2::scratch2::scratch2:
Now would be a good time for any kind of suggestions.
Tinman
09-22-2008, 04:21 PM
This is a long shot... but check the B+ capacitor for that supply. Also, check for a solid ground return.
I should have a look at my own DAT. I have a similar Sony and a Tascam, which never gives me trouble.
B+ is the positive power rail for most circuits. There appear to be a couple of decoupling capacitors near the driving circuit (10nF) plus a medium electrolytic I need to check where exactly sits.
"Solid ground return": Combined with the previous point, do you suspect lack of adequate current available and / or increased resistance reducing the driving current below the level that would keep the solenoid retracted?
Is is possible that a circuit unable to deliver enough current would deliver a peak (resulting in the solenoid kicking in) but not sustain it to keep the solenoid kicked in?
It does make sense to me. I am thinking that I should measure the voltage across the solenoid socket. Whatever I measure at the circuit needs to travel halfway across the PCB, go through the white ribbon cable to the drum drive board and then through the socket to the solenoid. Would it make sense to bypass all this and connect the solenoid directly to Q481?
I cannot suspect whatever exists from the ribbon cable to the solenoid as the fault remains with the PCB rather than follow the transport assembly. So, I am focusing from the ribbon socket to the LSI giving the initial pulse. I am still trying to find a proper spot to probe for the pulse. I think I need to switch to a scope - the DMM doesn't help that much in transient pulses.
I am also thinking to put the recent findings into use and check the failure mode back on the DTC-59. The circuitry is much less dense and somewhat neater in layout.
Tinman
09-23-2008, 10:14 AM
Well, it was a known issue when I worked in a shop that sony stuff of that era had a lot of bad solder. We did re-solder a lot of boards. That fixed many weird faults.
The white ribbons were replaced as well, though I still don't know what made them go bad.
The Capacitor in the B+ is a guess. I had a similar fault on a linear tracker TT. The tonearm solenoid would engage, but not stay locked. I bridged across the main cap for that supply.... problem solved. I replaced the cap.
The point is, I repaired so many "dogs" that I don't rule out anything anymore.
But... a quick test is to bridge the cap, and if that doesn't do it, run a wire from the transistor right to the solenoid connector to test the board. You could have a resistive solder connection. Yes, I have had those. Especially with the transitional junk when they went to lead free solder.
It's gotten better, but I still hate the new crap. Very difficult to work with.
Speaking of working with stuff, I am restoring an old STUDER mixing console. Talk about a DREAM to work on. EVERYTHING comes apart. Even the sliders are made to be serviced. Man, oh man... what quality. It's a pleasure to restore.
We'll NEVER see that sort of engineering again.
aldena007
09-24-2008, 11:30 AM
I am new to DAT decks and obtained one is a bizarre way. I was in an old recording studio and observed a Sony Deck that I thought was a cassette deck. I asked if it was a cassette deck and the owner of the studio said it was a DAT deck. This deck was at the bottom of a pile of other old audio equipment and he said I could have it if wanted it. It was a rack mount unit with a cassette tape stuck in it, but is really good shape considering. It powered up, but that was it. I gave me a strange error on the display. I opened it up and found that a tiny belt had jumped off a pulley. I replaced it and the deck works now. I am an old analogue cassette user and this thing is way too complicated for me. I am trying to find an operators manual. It is a Sony DTC-8A, but that does not bring up any information when I Google for it. It does record, but there are a lot of features I don't understand.
Anyway, on the old cassette decks that used solenoids, there was a configuration that provides full power to the solenoid to engage it, but this produces a lot of heat within the solenoid. A circuit was designed that would fire the solenoid (usually a capacitor/transistor combination) when the solenoid was engaged the voltage was dropped to just hold it against the load. I have seen conditions when the solenoid would not fire, but if you "helped it" it would hold the load, and then I have seen the condition you have described with the solenoid firing but dropping out.
I see a lot of IC's in my unit and the solenoid function may be handled by one of the IC's. On the old cassette decks it was easier to fix since it was more oriented to individual components.
Sorry about the long explaination. It may not even be revelant.
vincei
09-24-2008, 12:52 PM
I am new to DAT decks and obtained one is a bizarre way. I was in an old recording studio and observed a Sony Deck that I thought was a cassette deck. I asked if it was a cassette deck and the owner of the studio said it was a DAT deck. This deck was at the bottom of a pile of other old audio equipment and he said I could have it if wanted it. It was a rack mount unit with a cassette tape stuck in it, but is really good shape considering. It powered up, but that was it. I gave me a strange error on the display. I opened it up and found that a tiny belt had jumped off a pulley. I replaced it and the deck works now. I am an old analogue cassette user and this thing is way too complicated for me. I am trying to find an operators manual. It is a Sony DTC-8A, but that does not bring up any information when I Google for it. It does record, but there are a lot of features I don't understand.
Anyway, on the old cassette decks that used solenoids, there was a configuration that provides full power to the solenoid to engage it, but this produces a lot of heat within the solenoid. A circuit was designed that would fire the solenoid (usually a capacitor/transistor combination) when the solenoid was engaged the voltage was dropped to just hold it against the load. I have seen conditions when the solenoid would not fire, but if you "helped it" it would hold the load, and then I have seen the condition you have described with the solenoid firing but dropping out.
I see a lot of IC's in my unit and the solenoid function may be handled by one of the IC's. On the old cassette decks it was easier to fix since it was more oriented to individual components.
Sorry about the long explaination. It may not even be revelant.
Try DTC-A8. That's a nice machine with SBM I beleive. Lucky it was only the belt! Enjoy.
dr*audio
09-24-2008, 01:57 PM
Great thread, SaSi! I have a couple of comments. The pinchroller is very critical on all DAT machines. If tape alignment is not exact, you will have increased error rate, and damage to the tape. If you suspect the pinchroller, or if you are simply overhauling a deck that hasn't been serviced in a long time, replace the pinchroller with a new one. Messing around with other used rollers is a false economy, and may even prevent you from diagnosing other problems because of bad tape path.
Sony DATs use a bunch of micro switches to sense the position of the mechanism. Some decks, and I believe the ones you are working on, have a complicated rotary switch, located on the mechanism, called a mode switch. The switches get dirty and cause problems similar to what you are experiencing. If any of the micro switches are located on the questionable PC board, try cleaning them.
If you do end up having to replace the mode switch, you must mark the position of the switch, and the transport, and make sure not to move the transport while replacing the switch, otherwise the timing of the mechanism will be off. The correct positioning of the mechanism and switch will be in the service manual.
Anyone wanting to know about troubleshooting DAT decks should check out Eddie Ciletti's website: http://www.tangible-technology.com/
He is THE DAT GURU. If you get stuck, he will answer your e-mailed question, for a low fee; I think it was $15 the last I used it, and money well spent. He says the fee is per e-mail, but he will go back and forth with you a few times without charging extra, till he is sure you've got it right.
Tinman
09-24-2008, 07:53 PM
Ahhh... the dreaded mode switch....
BTW, sony had a few issues with the rubber suspension on some decks (in general) that outgassed and tarnished the little switches inside to the point of not working. A few minidisc decks actually had an internal service bulletin with a replacement kit for the switches and suspension bushings. However, when called on the phone, they denied any problem. I have been hung up on a few times when quoting THEIR part number for the fix.
Anyway, an unrelated bit of trivia.
dr*audio
09-24-2008, 08:17 PM
The Sony Professional people are much more helpful when it comes to DAT decks.
https://servicesplus.us.sony.biz/sony-parts.aspx
Tinman
09-24-2008, 09:44 PM
Yep, have an account. :D
Thanks for the comments and suggestions.
I have been a little quite in the past couple of days - I also have to work for a living - but will come back to it after the weekend.
Regarding sensor switches on the transports, there are the usual cassette in / media recognition switches (2 pins on the right side and 3 pins on the left side). For transport management there are 2 more switches mounted on the RHS PCB that receives the cassette in / rec enable sensors. These switches sense two positions in the mechanism: Arms extended and pinch roller engaged.
Perhaps the rotary switch exists in the older transports, e.g. DTC55 which has a totaly different beast of mechanism...
Regarding pinch rollers: I would be more than happy to buy 20 of those (it appears to be the same in all DAT transports). If only I had a source. At this moment in time, a shot roller means a dead deck.... Can anyone suggest a source for Sony DAT pinch rollers (bear in mind I live in Greece and not the USA) or some equivalent. I know there is this guy that re-furbishes them, but...
For the time being I do have a roller in excellent condition from a unit that was built in 2003 and died an early death being left idling due to head cogging.
From that unit and another one that operates wonderfully I must conclude that DAT transports should not be greased and lubricated. They appear to work much better after washing and cleaning with pure alcohol than when they are oiled or creased (as I've seen some faulty ones that users desperately tried to repair).
In the past two days I have been doing some offline testing and experimenting. I have tried several transports and several PCBs and discovered that there is only one PCB responsible for sluggish transport (the one of the DTC-ZE700). All the other transports suffer from worn out tension pads that stick to the spools.
I have also doublechecked my measurements and realized I was probably too tired or drunk or both when I did the first ones. Upon second inspection I realize that the transistor driving the solenoid does not close the circuit when the pulse is received even though it's base receives a pulse. I have removed that transistor for testing and replacement but tried the PCB without that transistor and it behaves showing the same fault. The solenoid kicks in but doesn't stay in. Therefore the initial pulse is provided from a different source and the transistor's function is to keep it there (or so I suspect).
I obviously need to spend more time reading the schematics and then try again.
dr*audio
09-25-2008, 08:17 AM
Isn't there a Sony parts center in Europe? I find that hard to believe. You can try http://www.doknet.nl/eng/index.html
He sells service manuals and parts.
Thanks for the pointer to doknet. Sent them an email and received a reply already. They do stock several spare parts I asked for and the price is reasonable, except for the pinch rollers where they stock the sony part that is the pinch roller mounted on the rotating plate at 30 euros.
I asked them if they stock the pinch roller by itself (which is the same part across all DAT units I've seen).
dr*audio
09-26-2008, 03:19 PM
I think the guy's name is Harri Brouwer. He's very helpful. You might offer to order 20 pcs to make it worth his while to order the pinchroller.
Yes, I explained to him just that, plus asked for a couple more items that seem to be common offenders.
For now I think I will put this DAT thing on hold. I am going through a pile of new acquired LPs, mostly Jazz, and they've grabbed my attention.
Tinman
09-26-2008, 06:17 PM
But....but......
I want to know the REAL culprit! This is my evening entertainment, you can't just leave me hanging! :cry:
dr*audio
09-26-2008, 08:30 PM
We will stay tuned....
But....but......
I want to know the REAL culprit! This is my evening entertainment, you can't just leave me hanging! :cry:
Me too...But I am more or less stuck with 1 faulty PCB on one deck and 4 faulty/sluggish transports.
I need to try replacing some suspicious parts as the cleaning that fixed some transports doesn't seem to fix these.
So, I am waiting for some RFC-300 motors, belts and hopefully pinch rollers (that's a besides the issue servicing as all old units suffer from deteriorated rollers)
medio_format
10-07-2008, 12:53 PM
Funny I should come across this posting today, I just bought a dirt cheap (75$) Sony DTC-59ES DAT Recorder in MINT condition but with just a few (I hope, minor) problems. żAre you planning on finishing this guide? You definitively should, our lives depend upon it!!! lol
The seller told me this machine always worked perfectly, but started failing some time ago. He said it correctly loads the tape, and that *sometimes* it might rewind a tape...but that it wouldn't play at all, nor rewind normally. I recently serviced an incredible Pioneer RT909 reel-to reel, the service included cleaning, replacing the capstan motor belt (gummy 70's plastic, groovy!) and the slippery pinch rollers for new ones. Worked like a charm! (for anyone interested, the original posting for that is in this same forum)
Although DAT machines are another story, from what the seller explained I suspect my faulty MINT 59ES could work again with some good tape mechanism/head cleaning, a new pinch roller and some minor adjustments. What do you think??
Looking forward to getting to see the end of the tutorial. :thmbsp:
Thanks, Carlos
Note: I have the service manual, in case you need it (I suppose u already have it, but just in case)
Hi,
I definately plan to continue and finish this service turorial. After a week of working with 4 different transports and 3 different decks on the (small) bench, life started getting a little miserable and the project started loosing it's appeal. Plus, I ended up needing some parts - my original donor transport ran out of bits and pieces to transplant.
The transports depicted on this guide are identical to the DTC59ES so the guide is totally relevant to your unit - it actually started on this deck.
From your description of the fault, it looks like the rotating gear that enganges the supply or take up spool on the transport doesn't work properly. This can be caused by dirt in the transport (as the deck is rather old), a weak spooling motor or too much tension in the spooling motor belt.
It might also be caused by a failed attempt to repair something. I've had two cases of such problems and these were the really easy ones to fix. One needed cleaning to remove tons of grease and the other needed replacement of the tape load arm location switch sensors.
In the week that passed since my last post on this, I did a little more work that I keep notes on but didn't post it as it mainly involves myself running in circles mostly.
I have "modified" a transport and removed the breaks and tension pads (that needed replacement). This transport has no breaks, no back tension and was thorougly cleaned and carefully lubed. It should have minimum of friction and tape travel should be nice and easy.
I have found that even this transport struggles to FF/REW a tape. 60 min tapes are ok, but 120min are moaning and 180min tapes struggle and 240min tapes don't make it to the end of tape.
Now, I know what most people write about 90 and 120 meter tapes and DAT machines (they are not compatible), but having 2 professional DAT units use them like a charm and also a couple of fully repaired consumer versions (DTC 670 and DTC55) doing the same, it feels like the concensous is a result of lots of units in bad shape having the same problem.
Anyway, I have just received a small lot of spooling motors at $3.95 each and I am planning to replace the motors on two transports that I cannot find anything else wrong with.
I am also doing some experiments on refitting tension pads where the original ones were reduced to a muddy lot of sticky substance and had to be removed. Without them there is no back tension and I can either over tighten the tension arms and get decent play but no FF/REW or keep them loose and get good FF/REW (too good and the deck stops thinking the tape is ended) but having no back tension it leaves me with playback problems as the tape get's curled off the capstan/pinch roller.
I am also looking for a source for pinch rollers. I am expecting a faulty computer DAT drive that might be a source for parts. The Dutch supplier Warren suggested seems to have everything but at 5 euro for bits and pieces each and 38 euro for a pinch roller, fixing a $20 faulty unit makes no sense.
I will be back in a few days (next week most likely) with some more feedback and progress. Most likely I will document the full stripdown of the transport for cleaning and lubrication. This has fixed 10 decks for me already and it is the hardest cases that were left when I started this thread, so perhaps the problems of these last decks are uncharacteristic of the majority.
Hi, I'm back with the DAT machines.
My donor DAT driver arrived and it was indeed a source for a pinch roller in excellent condition - and readily replaced an old one that showed cracking.
I also received a few spooling motor replacements that I am planning to try out.
In the meanwhile, I studied a disassembled transport and realized what I was missing. "How it actually works".
The transport must be clean, surgically clean. It's not bad to have some oil at the reduction gear shafts - I guess - but my bet is they are better off clean.
The two black clams that are pressed against the reels have a small cotton pad each that acts as the tension pressure pad. In one of the failing transports, the left reel pad was dislodged and sticky all over. On a second transport I had to remove both as it was filled with white grease and everything was sticky. I thought these pads are break pads. I was wrong...
Well, these pads are the secret for correct operation:
When in Play mode, the left one, if correctly adjusted, provides back tension to the supply reel. Not enough pressure and the tape gets mangled between the capstan and pinch roller. Too much pressure (i.e. adjustment screw missing) and tape movement get's sluggish, especially during FF/REW.
The first attempt to improve upon sluggish FF/REW was to increase the pot controlling forward tension. That had the side effect of making FF quite violent, especially at the beginning of a tape, causing the deck to stop. Too little forward tension and the take up spool won't rotate during play (especially if the tension pad is dislodged and sticky).
So, the repair/healing required is:
Total dismantling of the transport if it was lubricated (I did that on two of them), and thorough cleaning with alcohol, detergent, anything it takes.
Replacement of the tension pads with adequate material (still experimenting on this; found something that does the trick but have to find a way to make it last in position).
Adjustment of forward tension trimmer in 3/4 position,
Adjustment of back tension screw during play so that tape travels correctly through the capstan,
Fine tuning of the forward tension pot
Adjustment of S1, T1 guides for correct tracking,
Close the lid and enjoy.
I will continue with some experiments on replacing the tension pads and provide photos of the dismantled transport and points of interest in the next few days.
Hopefully, someone might point out a better solution for the pads.
Tinman
10-29-2008, 07:36 PM
SaSi,
You would really benefit from owning an ultrasound tank for cleaning. I SWEAR by mine, and I just got a larger one that holds 5 gallons and a small child. Now I can clean BIG things! YEAH!
A small tank that cleans jewelery would do those mechanisms perfectly.
ultrasound tank
What is this? Sounds interesting. Can you give me any links to products?
Soaking is feasible for certain types of PCBs even though drying them later takes some time, however there are things I could not think of soaking, like a complete Technics RS M85 that is full of sticky dust inside. I wouldn't dare striping it apart.
Tinman
10-30-2008, 09:21 AM
Here's just an example. 380077257324
I then dry with compressed air. You can also dry things in the oven at 140 degrees F.
And, believe it or not, most circuit boards clean just fine in the dishwasher. But the ultrasonic cleaner can do the same job in about 10 minutes.
I understand what this type of cleaner does. So, it also uses water.
:scratch2:Have you tried this to clean really filthy LP Records?:scratch2:
dr*audio
10-30-2008, 10:38 AM
For the pads I use felt. You can get it at craft shops and hardware stores (furniture slides / pads). The things you put under the feet of furniture to allow it so slide without marking the floor.
Good idea. But do these come ultrathin? Like 1~1,5mm thick?
After reading your suggestion, I was thinking of exploring using cassette tape pressure pads. The size seems almost right, slightly on the fat side.
dr*audio
10-30-2008, 01:33 PM
Craft Stores and fabric stores sell the thin stuff. It is difficult to find the really dense material, though. Some of the thin stuff just falls apart when you cut it into small pieces. You will have to experiment. If you can find anyone who makes hats, they should have the denser felt. May be some of that in Europe, but not in the USA.
Tinman
10-30-2008, 05:43 PM
I understand what this type of cleaner does. So, it also uses water.
:scratch2:Have you tried this to clean really filthy LP Records?:scratch2:
I'll try that when I set up the big tank. It cleans microscopically clean, so it should be fantastic on records.
OK, we are getting way-off topic here, but I was also thinking:
A square plastic container,
a heater,
a rotation mechanism mounted in the bottom of the container,
a KEF T27 mounted flush in the bottom in a small opening facing upwards,
a record rotated in the water
The tweeter has a plastic dome so it should be waterproof. And it can produce sounds in excess of 30kHz. And should be able to take 35~40 degrees (Celcious).
When you try that ultrasonic cleaner on vinyl, I guess it should be a good idea to start a relevant thread in the TT section.
Anyway, to get back to the relevant topic:
The original DTC59ES that was under surgery in the beginning of this thread is reassembled and undergoing a burnin test since last night. (repeating a 120meter tape with 10 tracks at no end. This tests play (and the tension pads I improvised) as well as rewind. And as the tape is twice as long as it supposedly should be handled by the deck, I will be happy if it passes the test for 24 hours.
When I get home, I will check and hopefully then post pictures of the cleaned and relined tension pads as well as describe the forward and back tension calibration + tape/head alignment over the weekend.
Well, the unit passed the test - almost.
Playback and FF/REW works great. No more curling the tape off the pinch roller (as back tension is there) and FF/REW is fast and stable.
But, one out of four times, ejecting the tape failed. The transport tries to retract the tape into the cassette but something is sensed wrong and the tape is extracted again. The cycle goes on 3 times and then the transport stops. It is required to shutoff the unit and upon power-up, eject succeeds.
Something to look into and a great excuse to strip down the transport once more and take detailed shots for your benefit.:music:
dr*audio
10-31-2008, 01:10 PM
Sounds like a switch problem, maybe the mode switch, or did you say this one doesn't have one?
Sounds like a switch problem, maybe the mode switch, or did you say this one doesn't have one?
I am not exactly sure what you mean by "mode switch". Apart from the cassette sense pin switches, the unit has two switches sensing the location of the slider controlling the tension arms and pinch roller. First switch senses "arms extended" and the second switch senses "pinch roller engaged", or so I gather from the state of the transport when the switches close.
Now, if this is what youi mean with "mode switch", you could be right, as I recall one of those switches to be rather abused and sticky - perhaps from too much grease.
In any case, a total stripdown is called for.
dr*audio
10-31-2008, 01:41 PM
Oh, THAT transport. I've worked on those. Those friggin' switches went bad after only a year or two. I'd check them out for sure. The mode switch I was talking about is a rotary switch about 20mm across with maybe 5 or 6 wires going to it, or a flat flexible cable. A friend of mine has a Sony that has one. I thought it was a DTC-690 but I'm not sure. Or maybe DTC-A7? If memory serves, the mode switch is located near the pinchroller, or to the right of the head. Those go bad all the time. VCRs had them, too.
Replaced the sensor board with one from the donor machine. It works like a charm now. 20 out of 20 cycles of load, play, ff, rew, play, stop, eject worked perfect. Thanks for the hint.:thmbsp:
Took some pictures of the process as well. I have now the transport in a state ready for alignment.
More to happen tomorrow.
Tinman
10-31-2008, 05:56 PM
Oh god yes, those switches are TERRIBLE. Both the rotary mode switches and the little push switches sony uses on the tiny transports. You should see the one's in the mini disc decks.
dr*audio
10-31-2008, 07:31 PM
The little microswitches used in the DTC-1000ES to sense the tape and record interlock are dodgy too, but I've been able to resuscitate them with cleaner and De-Oxit. Took a few treatments but they have been ok for over 2 years now. Digikey sells some microswitches and eventually I'll check them out as a replacement. Glad I could help. Sony has a bad habit of making the same mistakes over and over again. Grease that gets gummed up, tape guides in DAT decks that come loose and lose the height adjustment, using mounting screws on pc boards to complete ground paths on the board (screws get loose and you all of a sudden get poor ground paths, noise and dc offsets between 2 places in the circuit that are supposed to be ground.)
Nitro70
12-13-2008, 10:13 PM
The same kind of problem is found on several of the mechanisms used in DTC57, DTC 59, DTC670, DTC690 and DTC ZE700. All these decks use the same transport with minor differences on the first two models. There must be other models out there sharing the same transport, just haven't seen them all.
Hi,
After reading a major portion of this interesting thread I wanted to see if my Sony DTC690 would still work after it had been doing nothing for at least 3 years. It seems these Sony mechanisms are rubbish: last time I used it nothing was wrong with it and now, because it probably has been sitting too long doing nothing, it won't even load a tape anymore. The problem lies with the right spool, which for some reason won't turn around anymore when a tape is loaded. Because of this there is no tape tension, and therefore the loading fails.
Since I bought this deck that it has been sitting there more for looks then for purpose, only 25 tapes have been recorded on it: mostly 60 and 90 minute tapes, along with about three 120 minute tapes and one 180 minute tape. The whole unit it in mint condition, I even have the original packaging and because it probably now has been sitting too long doing nothing I can take it to a repair shop, which s*cks as repairs on DAT decks always cost $$$$$. Anyway, anyone who has ideas what the problem could be, as this unit has barely been used wear & tear would be a ridiculous reason.
A friend of mine also has had no luck with Sony DAT decks. His DTC690 ended up on the junk yard years ago, but at least he taped about 150 tapes with it. After that he got a DTC57ES, which again after 3 months began to show the same mechanical problems he had with his DTC690. So his 57ES also ended up in the trash. He now has a DTC60ES, which so far seems to be working reasonable... but he already has detected the first minor signs of the very same problems that surfaced with his prior two Sony DAT decks. If the 60ES fails he's never gonna buy a Sony DAT machine again :thumbsdn:, but get a model from Tascam instead.
Now that my DTC690 also has problems it appears to me that whatever you do with these Sony DAT decks you always loose: if you use them regularly they are prone to failure... if use them scarcely or put them back in their original packaging for years they'll also stop working.
Anyway am I looking at a reasonable repair or am I better of trashing my DTC690 after recording the a 'massive' amount of 25 tapes...
vincei
12-14-2008, 12:12 AM
Nitro70, I have had bad luck with Sony transports on certain decks. However, Sony's 4 head 4 motor decks are excellent, no comparison. Super quick, smooth, silent, all around superior. Of course this is my experience. I've had a DTC-59ES (failed), DTC-A7 (failed), DTC-87ES (ok 4H-4M), DTC-75ES (ok). I've also had a Technics SV-DA10, which was nice too.
...
The problem lies with the right spool, which for some reason won't turn around anymore when a tape is loaded. Because of this there is no tape tension, and therefore the loading fails.
...
Anyway am I looking at a reasonable repair or am I better of trashing my DTC690 after recording the a 'massive' amount of 25 tapes...
I can feel you. One of the decks I've received was delivered full with instruction manual and a pack of cut pages from hifi magazines with reviews. Raving reviews. The unit is a 690.
Once you study the Sony mechanism against, say, a Panasonic or a Technics, several small details become apparent on how simple things are kept simple and other mechanisms appear to be less prone to faults.
What is really a mystery is checking how a sony computer dat mechanism is designed. ALL the problems related with the Sony transports AREN'T there. Separate direct driver motors for each spool, no belts or pulleys, just gears and metal gears where torgue appears critical and high.
Regarding your deck's problem, my first reaction is: Don't trash it. The problem is bound to be simple to fix. This whole thread is about such problems.
I would like first to make sure of what the symptom is. We are talking about the right hand side spool, right? The take up spool. You load the cassette and the left spool is unwound but when the deck wants to move the tape slightly forward and backward to make sure it has been tensioned OK over the drum, the take up spool doesn't turn. Is that the symptom?
First of all, you can remove the deck's cover to verify tape loading and motion. It's not simple to do that through the small cover window. Or you can remove the cassette compartment cover for a better view.
The simplest reason I've seen that happen is because the cassette is faulty. when it is inserted in place, the front flap is opened and the bottom drawer cover is pushed back. This causes two spikes inside to retract from the geared reels and allow tape movement. Some cassettes sometimes don't release the RHS spike and that locks the reel in place. Just try a different cassette first.
A second thing to try is to repeatedly (>10 times) load and remove the cassette. Eject the cassette as soon as it locks itself in place, before the deck finishes the tape loading process. Sometimes, the "elevator" doesn't properly pull the cassette into proper position and the aformentioned spike is not retracted because of this.
Or the tape loading path might have been affected. If for example the tape isn't threaded through the pinch roller and capstan, it isn't moved properly and it shows as the RHS spool not moving. It could be that the pinch roller is bad.
If the above fail, then it is the turn of the transport to be examined. A violent removal of a cassette in the past might have broken or bent one of the tape guides (S1 or T1) and the tape might not be properly loaded.
Or, if a cassette was left inside the deck for years, the tension pads were set to press against the spool plates and they may have gone bad. Their glue is known to bleed and cause the tension arms to stick against the reel plates.
If you could take a video of the tape loading process through the cassette opening or the top (with sound), it would readily help identify what the problem is.
The 690 isn't a bad deck. The mechanism is the "most refined" transport of the consumer series and survived intact for a decade or so.
I have repaired a few of those and use one myself day today and given the other two to friends who run them daily for background music playing a 120m tape at half speed for 8 hours without any problems.
It might be worth to give it a shot at repairing it yourself, depending of course on how confident you feel with all things mechanical.
Nitro70
12-14-2008, 07:02 AM
Hi Sasi,
Thanks for all your help and suggestions.
Maybe I was a bit harsh, but as you can imagine I'm not happy to see that my DTC690, despite my discrete use, now also has mechanical problems. I used it discretely because I knew that a lot of Sony DAT machines were prone to such problems.
Although places that will still do repairs on DAT machines are hard to find these days, thank goodness I know one. To narrow things down somewhat. Prior to yesterday the DTC690 had been boxed during the last 3 years and was stored away in my bedroom.
I've never left any cassette in the deck for days on end without using it. Yesterday I also tried to load several cassettes, 60, 90 and 120 minutes - all to no avail, so I think faulty cassettes can be ruled out. It also does not matter if the cassette is completely wound back prior to loading it, I also tried to load one which is almost at its end with the same result. Since I bought this new, not one cassette has ever been violently inserted or removed from the deck.
Interesting thing detail is that the mechanism makes a soft squeeling noise whilst trying to tension the tape during the loading process. While observing the loading mechanism through the cassette door its 100% clear that the take up spool doesn't turn at all anymore.
I would like first to make sure of what the symptom is. We are talking about the right hand side spool, right? The take up spool. You load the cassette and the left spool is unwound but when the deck wants to move the tape slightly forward and backward to make sure it has been tensioned OK over the drum, the take up spool doesn't turn. Is that the symptom?
Yes, I confirm that this is indeed the EXACT symptom! I wouldn't be surprised if the problem is belt or pulley related. Beats me why on earth these were used in home audio DAT decks, whilst as you wrote, they weren't used in computer DATs.
One other thing you must know about is that despite the loading problem the digital counter of the deck will display an 'ABS time' which shows the position of the tape.
Once you study the Sony mechanism against, say, a Panasonic or a Technics, several small details become apparent on how simple things are kept simple and other mechanisms appear to be less prone to faults.
Besides the Sony I also have a JVC XD-Z505 (Panasonic mechanism): are you saying that Technics + Panasonic are less prone to faults because things were kept simpler compared to Sony mechanisms?
Thanks!
On Panasonic/Technics transports, there are simpler mechanisms and less plastic. Correction, no plastic on gears, pulleys and levers.
What you described appears to be a bleeding glue from the tension pad that has caused the pad to stick on the take up spool plate bringing it to a standstill. Do you live in a hot place?
It is good that the tape counter shows ABS and tape location. It means that the drum and alignment is fine.
gunnyjoe
12-14-2008, 10:34 AM
awesome thread THANK YOU! I have two SOny DATs one working and one not, following your guide here I think I can get the second unit going again!
Nitro70
12-14-2008, 10:45 AM
On Panasonic/Technics transports, there are simpler mechanisms and less plastic. Correction, no plastic on gears, pulleys and levers.
What you described appears to be a bleeding glue from the tension pad that has caused the pad to stick on the take up spool plate bringing it to a standstill. Do you live in a hot place?
It is good that the tape counter shows ABS and tape location. It means that the drum and alignment is fine.
That's why my JVC XD-Z505 (with Panasonic transport) probably still works fine... I tested this deck moments ago and it still is alive & kickin' :tresbon:
As for my DTC690: the place where I live can get hot during summer time. Although I always protect and if necessary shield all my audio- and video gear from direct sunlight at times during the summer the temperature in my living room can rise to about 29-30 C, which is pretty hot.
If the problem is caused by the pad being stuck to the take up spool plate: am I looking at something seriously, and more importantly would it be worth getting it repaired? As said, this DTC690 is as close to being mint as its gets, with only 25 tapes ever recorded on it, and play back hours have also been very modest.
Sometimes things break just because they aren't used. I know it sounds funny, but my Aiwa AD-F880 cassette decks developed a slack on the main belt just because I didn't use it much for a few years. It was 5 years old. I replaced the belt and used it regularly since then - 2001. It's working fine until now.
Tinman
12-14-2008, 12:13 PM
I have has sony's myself. But my Tascam DA-30 seems to go on forever.
Still, I like some of the Sony mechanisms. I think in general that prolonged non-use isn't good for any mechanical deck. Have to exercise the mechs from time to time to keep lubricants where they belong. I have had a few sony DAT's recently that just needed to be run a bit before they settled back in. On these, the brake bands were fine. The deck's just getting a little sticky. I suspect, though, that this is just the prelude to having to re-lube it.
Nitro70
12-14-2008, 12:43 PM
Sometimes things break just because they aren't used. I know it sounds funny, but my Aiwa AD-F880 cassette decks developed a slack on the main belt just because I didn't use it much for a few years. It was 5 years old. I replaced the belt and used it regularly since then - 2001. It's working fine until now.
Yes, this is indeed true - that's why it also is a bad idea to put a car for years on end in storage without ever starting up the engine. Even classic cars which could be worth millions need to be fired up and driving a bit at least a few times each year.
Anyway: I was hoping that you could indicate if my problem, which is probably as you indicated, caused by the pad being stuck to the take up spool plate, is something seriously or something that can be taken care of relatively easily?
Thanks!
Btw. Some basic small repairs on audio gear is something I sometimes do, but fiddling around with the delicate mechanism of a DAT deck is not my piece of cake - I'd much rather leave that to a professional.
Nitro70
12-14-2008, 03:27 PM
I think in general that prolonged non-use isn't good for any mechanical deck. Have to exercise the mechs from time to time to keep lubricants where they belong.
Tinman,
I think you're right - I should have used my Sony DTC-690 DAT deck a bit more intensively instead of keeping it as a mint backup unit to my JVC DAT deck. The JVC has been used more intensely and on a more regular basis and is an active part of my system.
Regarding 'exercising the mechs': do you think the same applies for cassette decks and VCRs? I have so many of these that only two of each are used regularly whilst the other ones remain vitually unused. If so, I'd have to set up 'exercise programs' for all of these.
There is a rather easy and safe way to check the problem on your DAT transport. It might also do the trick and fix it, although the chances are low.
If you can remove the top cover and then remove the transport mechanism as a whole (unplug the unit, slide and remove the outer cassette compartment cover, undo the 3 or 4 screws securing the plastic mounting of the transport to the base of the unit).
You don't even need to remove the wires from the main board.
Lift the transport out of the unit so that you can see the front edge of the mechanism, where the manufacture date is stamped (BTW what does it read there?).
To the left edge of the transport you can see a lever mounted on a rod driven by a solenoid. To the right edge you can see the reduction gears.
Use a clip, pen, screwdriver to gently push the left side rod inwards. This should release the reel plate brakes. Once this is done, you should be able to freely rotate the reel plates with your fingers. You should be able to rotate them even with the breaks engaged, but in that case you should feel a slight drag from the brakes.
If releasing the brakes makes no difference on the drag while rotating the RHS reel manualy, then the problem is a sticky tension pad.
Another test you might be able to to easily is to test the reel plate motor.
It is located underneath and it drives a toothed plastic band. You can rotate it to either direction. In one direction it should engage the supply reel and rotate that, in the other direction it should engage the take up reel and rotate that in the correct direction. It takes a firm spin with the pointer finger to make the inner "fly-gear" engage the proper reel. It might not be able to reproduce it manualy so the result of this test is not conclusive.
BTW, the sony transport mechanisms on these decks must not be lubed. They should run dry. the cleaner the better. Don't be tempted to spray WD40 or anything similar inside, it will only ruin the pads.
Tinman
12-15-2008, 10:57 AM
EEEEEEK!!!:yikes:
NEVER WD-40!:no:
But so many people do...
vincei
12-15-2008, 12:26 PM
After reading this thread again, I made sure to power up my mechanical transport components and use them for a bit to get the "Juices" flowing! ;)
I have to admit that my basement storage room has some magical abilities. Two units, one cassette deck and a DAT deck were briefly tested and stored with faults to be fixed. I left them be there for a couple of months. I brought up one of them to work on it, but it works. I gave it some time to fail but it doesn't. I am listening to some cassettes right now played on that.
I then thought, what the heck, it might as well be a DAT day today. So I brought that to the bench. It was supposed to have sluggish FF/REW and I was supposed to bring up some additional info to this thread. It works fine.
What's happening?
Tinman
12-15-2008, 08:30 PM
I have to admit that my basement storage room has some magical abilities. Two units, one cassette deck and a DAT deck were briefly tested and stored with faults to be fixed. I left them be there for a couple of months. I brought up one of them to work on it, but it works. I gave it some time to fail but it doesn't. I am listening to some cassettes right now played on that.
I then thought, what the heck, it might as well be a DAT day today. So I brought that to the bench. It was supposed to have sluggish FF/REW and I was supposed to bring up some additional info to this thread. It works fine.
What's happening?
Huh.... maybe it'll restore old tapes as well. :scratch2:
Nitro70
12-16-2008, 10:47 AM
EEEEEEK!!!:yikes:
NEVER WD-40!:no:
But so many people do...
I'll never use anything like that or try anything that I'm not the least bit confident about or familiar with, especially not with a delicate machine like a DAT recorder.
Nitro70
12-16-2008, 10:50 AM
I have to admit that my basement storage room has some magical abilities. Two units, one cassette deck and a DAT deck were briefly tested and stored with faults to be fixed. I left them be there for a couple of months. I brought up one of them to work on it, but it works. I gave it some time to fail but it doesn't. I am listening to some cassettes right now played on that.
I then thought, what the heck, it might as well be a DAT day today. So I brought that to the bench. It was supposed to have sluggish FF/REW and I was supposed to bring up some additional info to this thread. It works fine.
What's happening?
After reading that I think I'll let my DTC690 'rot' for a few months in a basement as well... if only I had a basement. Perhaps an outside somewhat moist shed would do the trick, that's where I keep my bicycles as well.
vBulletin® v3.7.4, Copyright ©2000-2009, Jelsoft Enterprises Ltd.