Servicing a SONY DAT machine (Pictorial)

I'd like to thank SaSi, hdrobien, and the others for all the excellent work in here. Also to mention is 12voltvids on YouTube.

I have a Sony DTC-670 from eBay, which was producing no audio output. Mechanically it appeared OK. Play, fast-forward and rewind worked. There were no levels on the VU meters, except for a random burst of activity, and the mute relay (RY301) was clicking all the time.

I did three or four rounds with the mechanicals, cleaning and so on. I had no confidence I was making any progress, and there was no change to the symptoms. I was concerned I was doing more damage than good.

I took a gamble on the RF Amp, and opened the can. Nothing appeared a problem - no leaks or stains. Following some comments in various fora (German and English) I replaced all 6 of the capacitors. The YouTube video from 12voltvids gave me the confidence to work on this. A rummage through my spare parts box, and the stripping of some RS232 TTL converters produced enough components. The soldering was done slowly and with care.

And it works! Wow. Less than a Euro of capacitors, and the DAT deck is back working. I've tested digital in/out, recording and it's fine. Playback of DAT tapes from various sources is fine - so I'm not going near the tracking or any adjustments.

I'm tempted to re-read the thread, and product a summary FAQ, which has a symptom to issue mapping, as the RF Amp appears to be a close second to dried up lubricant in causing issues here.

Thank you again guys...

Aidan
 
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Well done.

The RF amp capacitors failure is indeed the first issue, but surprisingly only concerns some specific models: DTC-57ES/DTC-670 and, to a lesser extent, DTC-59ES/DTC-690. Never had this issue with older or newer models but usually replace them anyway as routine maintenance.

Btw there are only 6 capacitors to replace: 1x 4.7 uF and 5x 22 uF.
 
Yes, 6 capacitors - just edited my post. Thanks.

Next on the workbench is a DTC-55ES for which I have a replacement gear from Dr. Gear on eBay, and I am likely to do the capacitors in the RF amp anyway.

Has anyone tried 3D printing to replace broken plastic parts?
 
So far I have only seen 2 replicas: the one from Dr Gear which is machined, and another one, molded in resin.
 
On the DTC-55ES, I replaced the broken rotary encoder gear with one from Dr. Gear - he's expensive, but the steel gear looks great. OK, so I forgot to perform the alignment from Page 14 in the Service Manual. Some dead ends, including dismantling the rotary encoder and cleaning it with an alcohol wipe (not a bad thing possibly).

I then spent a while trying to get the pinch roller to touch the capstan for the alignment process, but it's actually only supposed to line up with the capstan housing. A poor case of not RTFM correctly. Alignment is done. It looks like there's a positive tension used to keep the pinch roller on the capstan for playback, but in a "rest position", it's only close to the capstan housing.

I replaced the 2 capacitors in the RF Amp as a matter of course.

I had some problems with the pickup reels, and cleaned out some gunk associated with one of the break pads. I'm going to have to revisit this. FF/REW functions are still feeble.

Right now, it's been playing a DAT tape for ~30 minutes with no problems.

Left to do, is a full strip down of the circuit board based motor for the take-up spools, and see if there's more gunk jammed under the black plastic parts which act as part of the break mechanism. I suspect this is the reason for the slow/weak FF/REW.

Mangled a bit of one of my "test tapes".

I don't like the relay based mute system - it makes me think the tension is all bad, as it clicks away, and it's just really reacting to a lack of data stream from the head.

TL;DR...

broken rotary encoder gear -> new one from Dr. Gear -> Alignment process
slow/weak FF/REW -> clean out gunk under black plastic break mechanism over the motor
 
On the DTC-55ES I also usually do theses routine maintenance operations:
- remove and clean F guide arm as its pivot is generally stuck by hardened grease (same as the DTC-1000ES)
- re-crimp both S1 and T1 guides on their slant block.
- replace both felt pads on the T-shaped lever #562 as they become sticky. It will improve FF/REW.
 
The same DTC-55 ES is not rewinding - it appears that something on the take up spindle is not releasing. Play, FF and eject spool-up is fine. I need to do a complete strip down of the reels again. I have a donor 55ES that might give up it's FF/REW mechanism instead. The donor 55ES has some corrosion problems, and probably not worth saving. It was likely stored in a damp cellar.

I have a second DTC-670. I replaced the caps on the RF Amp, which turned out to be a bigger mess than I expected. I pulled off two of the circuit board pads while removing the old caps, and had a serious problems getting the new connections to work. In the end, one is wired to the underside with a patch cable, and the other with a second patch cable to another cap. Not much fun at all. It's still a bit crackley - I will replace all the caps (again) later in the week, and clean up the mess.

It had a second problem - there was a broken piece of plastic stuck in the Optical Out (IC322 GP1F32T), and I had to remove the main board, unsolder the TOSLINK transmitter, and split it up to remove the plastic that was stuck. Then put it all back together. This seems to have worked. The original Sharp GP1F32T/R appear to be no more, and the Farnell website is down today, as I try to get an alternative.
 
Wow, amazing that this thread is still going. My band's studio work from the 90's was all recorded to DAT masters. At $400 a crack or so to record each song, I've obviously been wanting to transfer the DAT masters into my daw.

That had been a problem. Either no local studio had a working DAT, or I would be required to mail them away to some unknown entity to have them put on CD (which I didn't want, I wanted them direct files).

Finally, last week I acquired a Sony DTC-A7 to use to toslink digitally into my Daw. I wet cleaned the inside and heads like crazy because this brown crude kept coming off onto the cleaning paper. Turns out- it was that Sony cleaning foam wheel which was deteriorating and randomly dropping bits into the head. I vacuumed this in order to remove the bits and the entire wheel disappeared! It must have broken up completely- but apparently I'm better off with it gone.

This unit appears to have some of the same issues listed here. When I loaded a tape, it sort of got jammed and wouldn't do anything. I used the hidden window underneath to manually roll back the rollers and then roll the tape back.

I reinserted this tape because it wasn't one of the masters, it started working and I was able to play this tape back from 2000. Hopefully it would be ok on a few other tapes.

I'd love to overhaul this unit and provide digital transfers for other people, I know I was reluctant to mail my masters to just anyone because you never know what condition the deck is in or how well they treat the tapes. I'm well aware that 1 dat can be worth a lot to someone.
 
Hello Team!
I want to buy some Sony DTC gear - I am looking at 57 / 59 or 60ES. Can you please recommend me one? First use will be as external DAC, second play from digital tapes. Which one will have the best sound? And which one will be the most solid and have less problems?
 
I would go for the 60ES, even they are very similar:
- All 3 share the same transport, with minor improvements for the latest.
- The 57ES has a slightly better build
- The 57ES and the 59ES are more prone to suffer from bad smd capacitors in the RF amp
 
I would go for the 60ES, even they are very similar:
- All 3 share the same transport, with minor improvements for the latest.
- The 57ES has a slightly better build
- The 57ES and the 59ES are more prone to suffer from bad smd capacitors in the RF amp

Many thanks for reply. And sound quality? It appears that D/A converter on 59ES and 60ES is the same. And I also noticed that 57ES is around 2kg heavier that 59ES or 60ES.
 
Hard to say about sound quality, it depends of own taste.

As I said the 57ES is slightly better built. For example the tape loading mechanism is made of metal sheet instead of plastic for the 59ES and the 60ES.
 
After reading all 33 pages of this forum, I don't believe I have seen anyone reporting the problem I'm encountering now, which is, my Sony DTC-670 will not fast forward but it will play and fast rewind. I have downloaded a service manual, so what I describe here is what I read from the service manual. When I press fast forward, it appears the F/R lever assy (part #369) won't engage with the take-up reel assy (part #366), consequently it will produce loud grinding sound as if the two gears are trying to engage in order to fast forward. I have taken the mechanism apart several times, remove all the sticky grease, cleaned all the mechanism, and had recheck everything but couldn't find anything else that needs to be fixed or adjusted.

Tonight, after studying the service manual, I noticed that on my machine, I don't see a washer (part #367) installed on the very top of the take up reel, so whenever I press fast forward, it will somehow push up the take up reel a bit and consequently the gear from the take up reel won't engage with the F/R lever assy, thus preventing the mechanism to perform the fast forward function. If I tap/hit the machine a bit while in fast forward mode, the gears will engage and it will fast forward. By the way, when I said it doesn't have a washer on the very top of the take up reel, I don't mean the washer pop out or that it's missing, I meant the take up reel's rod doesn't have an indent on the top to fit a washer. I find this highly unusual but I assumed it somehow worked for many years with out the washer from the previous owner. I'm quite sure if there is a way to install a washer to hold down the take up reel, it would solve this problem. First of all, has any of you heard of this before -- I would call it manuf. defect? If so, or if not so, how would one go about modifying the take up reel's rod to fit a washer on the very top?

There is one more unusual thing about this machine. The service manual indicate that there is a back tension solenoid spring (part #390) installed near the back tension solenoid but my machine doesn't have the spring. I suppose this can also cause the fast forward not functioning properly. If so, is there any where I can buy this spring?
 
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Continuing from my previous post, and for your reference, attached are two pictures of the take-up-reel where it shows there is no provision on the take-up-rod to attach a washer to hold down the take-up-reel.

Also, noticed that the back tension solenoid's spring is missing.
 
First, without washer #367 the take-up reel will be push upward because of spring #364, above the end of the rod, and probably scratch against the transport chassis. Check spring #364.

Second, I can see the spring #390 on both pictures.
 
To illustrate what I meant by the spring, please take a look at the attached picture, which was downloaded from this forum. As you can see, there are two springs, the big one is anchored right next to the back tension solenoid but there is another smaller spring that is installed on the back tension lever (part #380), which is what I'm referring to, which on my machine, it doesn't have this spring (although after studying it for a while, I'm not sure what is the purpose of the spring).

As for the washer on the take-up-reel, I probably say too much on my previous post. It's basically this: on my DTC-670, the washer is non-existent because the rod inside the take-up-reel doesn't have an indent on the top to allow installing a washer. So, my question is this: how do I go about fixing this issue so that I can install a washer on the rod, so that the take-up-reel doesn't slip upward whenever I press the fast forward button? By the way, on my DTC-670, I do see spring #364, but that is not the issue here.

upload_2018-6-24_4-42-22.jpeg
 
Ok, but it is not spring #390. It is something else on part #380. I wonder if it would not be an alternative for spring #399 which I can not see on the last picture.

And I can not undestand why there is no indent. Would the rod replaced ?
 
Spring #399 is attached to the solenoid, which is not what I'm referring to.

Concerning spring #380, if you look at the last picture that I posted, it's located just to the right of the large spring. Once again, from left to right: motor, large spring, small spring #380 (attached to the white color arm), then lastly the yellow solenoid.
 
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