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Sony DAT DTC-790 "Caution"

Brendan65

Brendan65

Member
So my Sony Dat deck has stopped working ... surprise, surprise !! :D
I got the "Caution" display and all functions stopped working, including the eject.
So I manually opened the door by rotating the pulley, and carefully removed the tape.

Right before it stopped working I noticed that the last cassette I loaded was difficult to insert. I now realize that the loading mechanism wasn't opening completely. It also stopped working and displayed the "caution" message when I tried to eject that same cassette.

I removed the drive mechanism and checked the belt - it seems OK but maybe it's stretched enough to slip before the door is completely open ?
I can only open the tape holder manually since the open/close button has stopped working. When putting a tape in and turning on the power, the tape seems to load properly.

I've done the search thing .. but I thought I'd throw it out there just in case ! :D

It's too bad - I've really enjoyed the deck for the 2 months I've had it ! :tears:
 
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If you have removed the transport mechanism (4 screws to the bottom of the chasis), then you should have access to a white horizontal gear slightly protruding at the right edge in the front. Try to rotate it in both directions. It should move the tape loading arms towards the drum and away from it depending on which way you rotate it.

If the two arms don't both move towards and away from the drum then the most likely cause is that a safety clip that secures the arm mechanism inside the transport has fallen off. Most common problem with these decks.

There's a sticky on servicing Sony DAT decks. It shows how to take a transport apart and fix such problems. It's long and full of pictures and discussions but don't be intimidated - it's a simple task.

I recently had the opportunity to fix a similar problem with a DTC-55ES. I confess to have done this several times and know my way around these decks, so I was able to remove the PCB in the back of the transport (3 screws) then the backplate of the transports (another 3 screws IIRC) and fix the problem without even dismantling the elevator from the transport. It took about 10 minutes to fix this.

A valuable piece of advice I read from another contributor. If the cylindrical clip is missing or doesn't fit snugly anymore, try using a 0.75mm gauge cable jacket cut at 2-3mm length. With a drop of super glue on the cable jacket, it replaces the safety clip more reliably.
 
OK - the loading arms are in the "loaded" position (forward, towards the tape drum).
Moving the gear counter-clockwise does nothing as the arms are against the stops.
Moving the gear clockwise, S1 moves about 2mm down the track towards the front of the deck, then stops (though the gear is still being turned.)
T1 doesn't move at all, though it wiggles like it wants to !

This is all I'll have time for today - back to reading your excellent sticky ! :thmbsp:

p.s. The deck was assembled on May 10, 1996 !
 
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All right - I went through the back of the transport - removed the pcb board and then the backplate.
Once it was apart, the loading arms moved freely when the geared "table" was moved sideways.

I couldn't see any missing clips and all the drive gears seemed to be engaging without slippage.
I re-assembled the transport and what do you know ... the arms now moved back and forth when spinning the gears !

So I put the remaining parts all back together - powered on - and all appeared normal and working properly. No caution message.
It didn't make sense that it could be fixed by simply taking it apart and putting it back together. So I got a tape and it loaded properly and all the functions worked ... until I tried to eject it. Then the arms (specifically T1) gets stuck in the loaded position and won't move. (Caution message appears)

Sigh ... not sure what to do now, other that take a break !! :D
 
Whoa .. I was dejectedly putting the deck aside when I noticed this rolling around inside the chassis :

os98xg.jpg


Looks like a missing clip to me !

Now I just have to figure out where it goes - and whether or not it needs to be glued. :scratch2:

Renewed optimism !! :D :D
 
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Once more, carefully read Sasi's sticky post, it's a goldmine for DAT fans.

I would recommend message #27: your clip probably goes on one of the arm pinions. I recently repaired a ZE700 and a 59ES suffering from this problem.
 
hdrobien said:
Once more, carefully read Sasi's sticky post, it's a goldmine for DAT fans.

I would recommend message #27: your clip probably goes on one of the arm pinions. I recently repaired a ZE700 and a 59ES suffering from this problem.
Click to expand...
You were correct .. it was this clip that had popped off :

11m9s2v.jpg


I re-assembled the deck - but the problem isn't fixed ! :tears:
Maybe the clip popped off again right away ?
Sigh ... I'll keep at it.
 
The picture is not big enough to be sure but I think you misplaced the white arm pinion.

If you look carefully the white pinion has a larger dent that should fit the notch on the dented part of the sliding white "bridge".
 
hdrobien said:
The picture is not big enough to be sure but I think you misplaced the white arm pinion.

If you look carefully the white pinion has a larger dent that should fit the notch on the dented part of the sliding white "bridge".
Click to expand...
That is Sasi's photo from the sticky - I just used it to show which clip had come off.
But I didn't realize the pinion/bridge fitting part - I just stuck it back together without noting the notch etc.. :sigh:

I'll get it eventually ... hopefully .. :D
 
Whoo-hoo !! Everything appears to be working now ! :thmbsp:
All functions (play, ff, etc ..) and I've loaded and ejected the tape 5 times with no problems.
I'm still not sure what the problem was/is .. as the last "repair" I did was only to manually remove the tape that was stuck in there. I spun the loading arms back and forth easily, so I just put it back together.

I did notice that T1 sometimes sticks with a slight "click" when it reaches the loaded position. Not sure if that's normal ? As it seems as that is where the hang up occurs.

Anyway thanks Sasi and hrdobien !
I'm sure my DAT deck is good for another solid week of use !! :rolleyes:
 
SaSi said:
If you have removed the transport mechanism (4 screws to the bottom of the chasis), then you should have access to a white horizontal gear slightly protruding at the right edge in the front. Try to rotate it in both directions. It should move the tape loading arms towards the drum and away from it depending on which way you rotate it.

If the two arms don't both move towards and away from the drum then the most likely cause is that a safety clip that secures the arm mechanism inside the transport has fallen off. Most common problem with these decks.

There's a sticky on servicing Sony DAT decks. It shows how to take a transport apart and fix such problems. It's long and full of pictures and discussions but don't be intimidated - it's a simple task.
Click to expand...

Hello SaSi,
Well, 7 years later, your post seem like my best chance at resolving my A8's "caution" light...(door won't open).
Where can I find that "sticky" you referred to. Thanks.
 
Hi

The A8 does not share much with the 790 and problems are different.

First check: remove the cover and look for the belt on the left side of the transport. Is it ok ?
 
hdrobien said:
Hi

The A8 does not share much with the 790 and problems are different.

First check: remove the cover and look for the belt on the left side of the transport. Is it ok ?
Click to expand...
The belt is good. Turning it's wheel manually turns the larger gear which then opens the transport. Turning on the power then causes it to shut the transport, then displays "caution".
The open/close button is inoperative.
Thanks for getting back!
 
Ok

Could you take pictures of the transport ? I would like to see position of the pinchroller and all guides.

If you have contact cleaner (deoxit), spray on all switches. They are usually green and located on the side, near the pinchroller and under the lower side of the cassette. Protect the head-drum.
 
Thanks for the pictures, nothing obvious found.

Additional questions:
- Does the drum freely rotates ? (with your finger on the top, not on the side)
- Are both guides fully retracted ? (can't see on the pictures)
- When the door closes with a tape, do the guides extend (or at least try to) ?
 
hdrobien said:
Thanks for the pictures, nothing obvious found.

Additional questions:
- Does the drum freely rotates ? (with your finger on the top, not on the side)
- Are both guides fully retracted ? (can't see on the pictures)
- When the door closes with a tape, do the guides extend (or at least try to) ?
Click to expand...

When opening and closing door by manually turning gear on side, there is no movement of any arms.
When tape is inserted, then power turned on, tape goes in, but still no arms, and no tape threading.
While power is still on, manual turning of gear is stopped.
Power must be turned off for manual tape ejection.
Thanks again.
 
Ok

- Does the drum freely rotates whith your finger ? (or does it rotates by itself when powering on or off ?)
- When tape is inserted, then power turned on, do you hear any motor spinning inside the transport ? (the motor that drives the arms)

The motor and gear on side are only loading the cassette shell in and out. There is another motor inside that drives the arms and the pinchroller. It uses a belt that could be stretched. That is why I am asking you if your hear any noise.
 
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