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Servicing a SONY DAT machine (Pictorial)

jan_stevns said:
8mm decks ? which are you thinking of
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Most of the early stuff, including the camcorders. I don't know if Sony ever fixed that and don't care. But I did a LOT of guide gluing with locktite in the late 90's to early 2000's. They would just unscrew after a while. And the itty bitty set screw wasn't always accessible without taking the whole mech out.

Marc
 
Hello everyone.

I just found this fantastic message seeking help for a problem on a DTC-59es I just get a nominal price. The mechanism seems to work (loading, playback, forward and rewind), but no sound comes out. The level meters does not move, the sampling frequency indicator flashes. The meter is running.

I tried cleaning the head but nothing changed. Once or twice the device was thought to recognize a "start id" but that's all.

Any idea ?
 
heads could be dirty or worn beyond use - don't clean these heads by hand, in a shop selling backup medias for DAT's you may find a cleaning tape for backup devices, they can be used for Digital audio Tape decks as well ....

If the heads are dead, it's a pretty expensive task you're facing.
 
Another interesting finding: with a 60mn tape (recorder in long play mode) instead of 120mn i have much more start id / sampling rate detections and meters sometimes move.
 
Probably best if you start a new thread specifically about your issue. Likely you will get more info that way.
 
Bigerik said:
Actually, this thread is so good, it deserves a sticky. Thanks Sasi!
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You are welcome. It was a nice surprise to see it stickied. I actually will need to reference it again as I pulled out several transports that need repair or will become donors and plan to fix a couple of them.

It has been more than a year that I last worked on these transports and some details are now forgotten.

What I still recall is that these transports should NEVER get greased or oiled and that the main issue with them is the felt pads that are responsible for braking and back tension. They either stop generating any friction or become sticky and the spool locks up easily. Still need to find a correct fix for these.
 
SaSi said:
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.
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Just read your problem. From past experience of CD, VCR, R to R repairs. I note on your drawings that the drive circuit is noted as PWM-Buffer. The PWM usually denotes a Pulse Width Modulator. It would seem that the signal coming in from TPWM will be a square wave from a uP port which is filtered by R481/C481 to give the average DC voltage which is buffered by the IC and then drives the Solenoid via Q481 which is meaty enough to handle the solenoid. If you use a scope on the DC voltage you may see a high "Pull In" voltage which drops to a small "Hold Voltage" after the solenoid has pulled in. This may happen in less than a second which will not be picked up by an analogue meter or DVM as they will not respond fast enough. Try cleaning the solenoid plunger and housing. There may be dirt or grime which is preventing the plunger from fully seating which will render the hold voltage insufficient.
Hope this helps

GPS16
 
SaSi said:
You are welcome. It was a nice surprise to see it stickied. I actually will need to reference it again as I pulled out several transports that need repair or will become donors and plan to fix a couple of them.

It has been more than a year that I last worked on these transports and some details are now forgotten.

What I still recall is that these transports should NEVER get greased or oiled and that the main issue with them is the felt pads that are responsible for braking and back tension. They either stop generating any friction or become sticky and the spool locks up easily. Still need to find a correct fix for these.
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Hello Sasi

Thanks to your excellent post I was able to repair a "DTC-59ES" and a "DTC-55ES". I bought them both for a few euros and they were in very good cosmetic condition (and with wood panels).
The DTC-55ES: I disassemble and clean the mechanism (and of course the case).
The DTC-59ES: the RF amp was dead, but I was able to retrieve one on a DTC-690 in wreck condition.

After much work I was also able to even rehabilitate the DTC-690: the case was dirty behond imagination, belts were dead, the loading mechanism had exploded and above all the axis of rotation of one of the arms was broken. I fixed it by inserting inside a piece of metal pin to secure.

To finish the job I wanted to know if it would be possible to recover some parts from your wrecks (against payment of course)?
- One foot (with rubber sole) and the door cover for the DTC-55ES
- The RF amp for the 690/59ES

Thank you in advance.
 
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I have a 59es and a 700.
The 700 I smoked by dragging an rca plug across the power supply. Creamed the logic as the capstan motor ran full speed, the display showed "pretty flashing segments" nothing worked and I WAS PI$$ED!!!
That was about 15-20 years ago.
I used my port-a-dat for a while (a Sony TCD-D3) until I saved enough for a 59ES.
Well fast forward (hehe) to 2005.
The 59 would not load/play/FF/RWD. DAMN!!!!
Took it a part and found the grease had turned into glue for the threading gear train! Same thing that SaSi has been talking about.
Cleaned all the "goop" and it threaded like a dream BUT still didn't RWD/FFWD/play. THEN found that the reel tables lub had also turned to glue.
Cleaned them and now tape moved BUT would NOT playback/tape counter would not move.
Looked deeper and found that the RF amp was not outputting good signal.
Took the RF amp apart (opened it up), scoped some signals (I have the service manual... could not do it without one!), and found weird things happening.
Looked REAL close and one of the surface mount electrolytic caps had "farted" it's elctrolyte onto the board, disolved the copper under it and had enough leakage current to pull an input to the amp to +5 volts.
The cap in question was C22, a 4.7 uf cap that was between pin 8 "envelope peak" and +5 volts.
A copper trace that passed under the cap went to pin 6 of the same IC "envelope out". This caused the AGC portion to change the gain of the RF amp so that it mis interpreted the level and destroyed the closed loop portion of the AGC.
Just replacing that cap revived my 59ES!!!!
BUT it took ALOT of CLOSE investigation and probing. I am once again a happy DAT user!
The port-a-dat (the D3) had problems of it's own... the T1 and S1 guides decided to "auto adjust" themselves. This meant that they would unscrew themselves when a tape was loading, and screw themselves back when a tape was loading!!!! Thank goodness they didn't come apart and get wrapped up in the drum, or I possibly would have broken heads!!!! I did my best to adjust them for no tape curl (yeah RIGHT) and a good RF envelope and am once again happy. It still, once in a while, has problems unloading where it will fail, and I have to press eject again.
SaSi.... did you ever come up with a procedure for the 59 on adjusting the back tension solenoid? I just kinda did it by watching the curl around the capstan, but wanted to know if you had any better procedure?
I can attach a block diagram/RF amp board layout with the C22 cap problem is anyone is interested?
 
popmonabill2 said:
... SaSi.... did you ever come up with a procedure for the 59 on adjusting the back tension solenoid? I just kinda did it by watching the curl around the capstan, but wanted to know if you had any better procedure?...
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The short answer is ... No!

I tried several things and some worked sporadically.

The procedure is to adjust the screw in order to get enough friction but not too much. I suppose the difference between inadequate and too much may be less than a quarter of a turn.

There are two reasons for this.
This adjustment can't really be made without a torque measurement cassette
And
The back tension issue cannot be resolved before a proper replacement pad can be found for the "brakes".

At one point I was lucky to be able to grab a couple of torque measurement DAT cassettes. But they arrived shortly before I was moving from my appartment to a new home. Supposedly I have plenty of room now to do such work and fix those DATs, but unfortunately betwee day work and gardening and resting a bit, there is hardly enough time.
 
I hope it's ok to ask on this tread than to open a new one.

I have been offered a Sony DTC 55 ES, it has been very well taking care of, cosmetically perfect, side panel's, remote , box, but it has a problem.
It will not rewind the tape at the beginning when cold and everything work's after the unit warm's up .

Is this a common problem with this Sony model !?

How fixable is it ?

Thank you -any help appreciated !
 
steve_pan said:
I hope it's ok to ask on this tread than to open a new one.

I have been offered a Sony DTC 55 ES, it has been very well taking care of, cosmetically perfect, side panel's, remote , box, but it has a problem.
It will not rewind the tape at the beginning when cold and everything work's after the unit warm's up .

Is this a common problem with this Sony model !?

How fixable is it ?

Thank you -any help appreciated !
Click to expand...

It is very likely fixable. A thorough cleaning of the transport is certainly required. Hopefully the pressure pads have not given up.
 
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