Servicing a SONY DAT machine (Pictorial)

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.
 
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.
 
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.
 
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.
 
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).
 
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.
 
But....but......

I want to know the REAL culprit! This is my evening entertainment, you can't just leave me hanging! :cry:
 
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)
 
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. ¿Are 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.
 
Back in the game - anyone still cares?

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.
 
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.
 
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:
 
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