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Servicing a SONY DAT machine (Pictorial)

First of all, let me tell you that I'm very impressed by the quality and the activity of this community, long life to music-lovers :music:

here goes my first Post in this forum....

I quickly switched off my hifi rack when a strange smell of burning electronic components hit my nose :boring:
just after this incident my Sony DAT dtc-670 refused to play any sound , although all mechanical parts and illuminations are working fine, the bar graph shows no sign of modulation signal anymore..,
I might suspect some power supply components but there is absolutely not sign of damaged electronics on the various boards.

Did someone already had similar experience ?

All comments and advices are welcome :yes::yes:
José
 
If the display and the mecanism are operationnal i won't suspect the power supply.

If you have access to another DAT player you can try to record something with your 670 and then play the tape on the other player.

If the tape is indeed recorded the problem is probably on the main board. Otherwise you can suspect the heads or the RF amp.
 
Thank you for your reply,
OK, I'll check out on another DAT machine.
I wonder which one of your possibilities is the best ;-(
J.
 
Thanks to all

I would like to thank everyone, but SaSi in particular, for the suggestions. I successfully repaired a Sony DTC-690, using the pictures and comments.

The service manual that I found on the internet was not very helpful, as it does not describe the procedure to take the mechanism apart.

With my machine, a bushing was missing. The T1 guide did not move properly.

The part was obtained from vento.nl (rather expensive, about EUR 8 plus shipping). But a working machine as a result.

A picture indicating the problem is attached.

Thanks again!

Henk Jan
 

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Regards to all the guys this is my first post...
I have three DAT machines, two 55ES, 59ES one.
On 59ES I successfully solved the problem with missing clips on T2.
55es generally have the problem that when the cold will not rewind the tape. After cleaning everything works great.
My first 55ES looks like it survived the Second World War, everything is in the process of decay, but work as a clock.
Other 55ES looks like it is now taken out of the factory but has a problem with mechanics. I tried to change my mechanics from one to another and always the same problem with same mechanic.
For now, the failing DAT I use as a DAC, but I would like to again in working condition.
The problem is that when you set tracking on one tape, the other is not working properly, when you adjust for it does not work with the third. But all the tapes work perfectly in other DAT 55ES, 59ES and 77ES. Tape is 100% correct. The next problem is that the cassette that was recorded on it to hear music with intermittent audible clicking of relays. This DAT tape played on other machines result no sound only digital mistakes with music periodicaly 1 second and no sound again.
The head is pure, mechanics look like new.

Is there any idea ...

My english is bad, sory for that. I hope you understood me..
I am from Serbia.
 
uzvarb said:
Regards to all the guys this is my first post...
I have three DAT machines, two 55ES, 59ES one.
On 59ES I successfully solved the problem with missing clips on T2.
55es generally have the problem that when the cold will not rewind the tape. After cleaning everything works great.
My first 55ES looks like it survived the Second World War, everything is in the process of decay, but work as a clock.
Other 55ES looks like it is now taken out of the factory but has a problem with mechanics. I tried to change my mechanics from one to another and always the same problem with same mechanic.
For now, the failing DAT I use as a DAC, but I would like to again in working condition.
The problem is that when you set tracking on one tape, the other is not working properly, when you adjust for it does not work with the third. But all the tapes work perfectly in other DAT 55ES, 59ES and 77ES. Tape is 100% correct. The next problem is that the cassette that was recorded on it to hear music with intermittent audible clicking of relays. This DAT tape played on other machines result no sound only digital mistakes with music periodicaly 1 second and no sound again.
The head is pure, mechanics look like new.

Is there any idea ...

My english is bad, sory for that. I hope you understood me..
I am from Serbia.
Click to expand...
It is likely that the transport is worn to the point that the azimouth adjustment doesn't remain fixed. It's also possible that there's a fault (or dirt) on the flywheel head. It's hard to be certain.

I've had decks presenting this kind of problem and a few were "fixed" by repeatedly recording silence with them on a brand new tape. When recording these decks do not check for errors (don't have monitor capability) so they will record even with faults.

This is a nice way to "clean" the transport and "burn it in" once more, especially if it was left unused for years or decades.
 
Thanks for your reply SaSi. I will try to complete disassembly of mechanics and to apply a deep cleaning.
Also I think that is defective electronics that are located on the mechanics and it is connected cables from the head. Is it the RF amplifier?( DTC-55ES )
I am from my DAT remove a proper mechanics and installed it in the DAT which is in mint condition. This now works great.
On a DAT deck (55ES and 77ES ), I entered the experiment with a pinch roller that looked like the one that set the SaSi at the beginning of topics. That was 2 years ago, and the unit operates to this day great. The experiment was successful, and as I applied to several devices and all work great.
If anyone is interested I would have gladly shared it with you.
I only have to prepare a photo and description of this simple repair that returns the pinch roller in operation.
 
Hi Sasi,

I'm very glad that i've found your topic, maybe you can help solving the problem.
My 670 DAT recorder wil load the tape fine but then something goes wrong.
It will not play the tape and ejecting the tape issn't possible.
(only after turning off)
The left reelside works but the right side doesn't
Can you help me out?
 
I have seen a few DAT decks that have the take up spool (right hand side) sticky. The result is that when the tape is loaded and the take up spool needs to rotate to tension the tape, this doesn't happen and the tape remains loose.

Typically, if this happens, the tape will get mangled along the rotating head wheel, more tape will be extracted from the cassette and you get a mess in the transport requiring to destroy the tape in order to remove it. If you are lucky you can eject the cassette without messing it.

I can't say I know all the reasons for this happening but on the 670 that would mean that either a retaining bracket is loose - causing the cog rotating the take up spool not to engage - or there's dirt or solidified grease that's inhibiting the rotation, or - finally - the break pad around the take up spool rod is worn and it's glue agent spilled on the take up spool or / and it has accumulated dirt and is engaging the spool.

In every case above, what is needed is a careful opening of the transport, separation of the top and the bottom part, and thorough examination for the casue of the problem. A cleaning on such an old deck is always welcome.
 
SaSi said:
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,
Click to expand...

Hello SaSi

I am trying to repair my DTC 670 and after removing the mech I find it passes all your suggested tests but it does not play sounds and forward Rewing is sluggish.

Would you please explain where the forward tension trimmer is and the forward tension pot ?

Regards

Ricardo
 
The forward tension trimmer and forward tension pot are one and the same. Sorry for the confusion.
IIRC the trimmer is located on the main board, to the front, left hand side of the board. I think it's the only trimmer mounted on the board.

3/4 is a rough adjustment but to fine tune it you will need a tension meaurement tape. It does make a difference if it's fine tuned (same as back tension) but you really can't get it totally right unless you can measure it.
 
I dismantled the transport (thanks to your detailed fotos and text), cleaned the gears and the excess grease on the white bridge and now the player loads, unloads, forwards and rewinds perfectly.

In play mode, there is good tension on the pinch roller and the tape contacts perfectly with the rotating head but... there is no sound. The metter does not indicate any signal.

What should I do ?
 
I assume the cassette is recorded, right?

It's possible there's a fault or it's possible the head is mis-aligned or is dirty.

What I would do with a suspect deck would be this:
Take a long tape (3 hours) and record (silence or whatever) on it throughout. At random intervals press the write ID button. This tape will serve you as a "cleaning" tape from now on for such suspect decks.
When the tape finishes, rewind and play it back. Check if the time counter advances. Check if the track mark counter advances. If these things happen it's a good sign - the markers are recorded on tape and read back succesfully.

Repeat this with the same tape 2-3 times. If the head was dirty (or accumulated dirt due to sitting idle for years) it will eventually start reproducing sound - jerky and with artefacts mostly but even that is a good sign.

At that point it might be a good thing to use a proper cleaning tape on the deck. The problem is, they are hard to find, expensive and short in tape run. And a dirty head needs a lot of tape run to loose accumulated grit. So I prefer to use a normal tape.

If you don't see any response (track marker counter or time counter) after repeated attempts, then we need to check different things.

Head mis-alignment might be an issue but I've found that slight to moderate mis-alignment will not result in failure to record and playback a tape on the same deck. It will simply mean the deck will fail to reproduce tapes recorded on a different deck.

Try the above and come back with your results.

BTW, regarding the forward tension trimmer, it might be that the 670 doesn't have one. IIRC, there's one or two Sony models that don't have this and the DTC-670 (being a low end unit) might be one of them.
 
I left the player recording for 6 hours now and there are no evolutions.

How can I check adjustment of S1, T1 guides for correct tracking ?
 
I believe there the issue is somewhere else.

I must get a schematic and hopefully some repair guidance for the electronics. Can you help me SaSi ?

For now I will bench the machine. It works as a DAC... The transport works but there is no sound :(
 
SaSi said:
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.
Click to expand...

I'm in the process of removing the transport and have disconnected 3 of the wire harnesses but am concerned about the flat white ribbon. You stated "The white flat ribbon cable is attached by pressure to the ribbon socket." It does not appear to have an outer housing like the other three and before I attempt to remove it, how should I proceed? If it simply pulls out of the socket, how does it line up to be refitted?

Why am I even doing this? I bought a PCM-R500 from eBay and the transport runs fast. I'm no service tech, but believe the pinch roller to be inside the case and possibly wedged somewhere and hidden. I spoke to prominent DAT facility in NY or NJ and based on the symptom, the initial speculation over the phone was a cracked pinch roller cover. Another forum thread corroborated a similar response to someone else with the same symtom:

Sounds like the pinch roller is your likely suspect...Common issue with them coming off the arm.
There is a plastic retaining cap that usually cracks and causes the pinch roller to come off...
If you can find it inside the deck, you can easily put it back on (pinch roller and cap) with a slight touch of nail polish to top it off to keep it locked in.
Click to expand...

That's why I'm in my deck, but I'd like to remove the transport wiring to be able to freely inspect all possible places the capstan could have been wedged into (it's not on the roller where it belongs) and also maybe find the cap. That flat white wire is all that's left to remove and it worries me to do so without a little more info so as not to damage it. Thanks in advance, I can't believe the talent and skill collected here at AK, and this guide is a prime example! :-)
 
Problem on a new addition to my collection, a DTC-690. Sound is distorded on both outputs: analog and digital (optical). Mecanism seems clean and everything else runs fine (transport, time counter...).

I was able to switch heads and RF amp with another transport but no improvment (that is supposed to run fine). I also tried a cleaning tape.

Any idea ?
 
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