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Servicing a SONY DAT machine (Pictorial)

Hi @hdrobien, i have a question.

With the deck in test mode, should i hear sound when playing the tape at x1.5 speed (AMS -->| ) ?
Also should i hear sound with ATF set to off (Rec mode set to std) ?

I have a tape that i know the first few minutes are bad (head B showing much lower signal than head A) but the 2nd track is ok.
However my 3 other decks can play fine this portion of the tape. The last one i bought can't play the bad part of the tape but can play fine with good signal on both heads the 2nd track if adjusted.

I wondering if i need to adjust both T1 & S1 guides to bring the whole tape up or down against the head insted of changing only the angle.
 
Hi

Hard to say, as I never use the test mode + AMS with audio recorded tapes, only with tracking test tapes.

But you should hear audio in play mode, whatever the ATF setting.

Concerning your second question : hard to say as some decks have much more "tolerance" than others (possibly related to a lot of factors).
 
Hi @hdrobien


hdrobien said:
But you should hear audio in play mode, whatever the ATF setting.
Click to expand...

Mine doesn't do that... When i turn off the ATF, the RF signal progressively is getting lower and lower, to the point that the deck can't keep up and mute the output...
(about 4 -5 seconds from the moment that i will turn off the ATF)

But the RF envelope is still fine, only lower than before... I Don't know what that means.... trying to adjust the guides at this point only make it worse.

hdrobien said:
Concerning your second question : hard to say as some decks have much more "tolerance" than others (possibly related to a lot of factors).
Click to expand...

I don't think this is the case for me: I'm comparing a DTC-75ES with a DTC-55ES (same model for those who don't know).
The new 75ES can't read the tape, while the 55ES can.


I also swap the transports and RF amps between the 2 decks, The problem is following the transport. It's not the electronics or the RF amp.
 
Dimitris_ said:
I know but he didn't touch it in his video, that's why i mention it.

Maybe he thought that the spring keeps back the whole gear??

Can't be anything else. This or the rotary encoder is misaligned or dirty.
Click to expand...
The video was made before dismantling the gears.
I confirm that everything slides freely and the silver hook moves freely against the black gear.
Nothing is bent. The encoder is clean. Zero old grease residues.
The black gears are synced between them (with the hole) and the encoder realigned in all possible positions.
No matter what I do, the pinch roller gets engaged during fast forward or reverse.
A-B gears and encoder gear are brand new. Tried all 3 sets I have (3d printed, stainless steel and brass) but...nothing.
Thanks!
 
Hi @hdrobien,

This video is with a good condition tape (don't know if recorded with an aligned deck or not) , Test mode on, offset set to 0 (timer set to off), playback x1 speed.
Look what happened when i turn on and off the ATF switch. With ATF off it's impossible to align, signal goes up and down all the time.

At some point i made it to produce sound at 1.5x speed (AMS -->| ) but when i test it with x1 speed the results was not good.

 
vallentin said:
The video was made before dismantling the gears.
I confirm that everything slides freely and the silver hook moves freely against the black gear.
Nothing is bent. The encoder is clean. Zero old grease residues.
The black gears are synced between them (with the hole) and the encoder realigned in all possible positions.
No matter what I do, the pinch roller gets engaged during fast forward or reverse.
A-B gears and encoder gear are brand new. Tried all 3 sets I have (3d printed, stainless steel and brass) but...nothing.
Thanks!
Click to expand...

Does it read the ABS time from the tape when in this mode?

I manage to *somehow* reproduce your problem yesterday when i was trying to fix mine.
I say somehow because it did it only in AMS -->| mode (next track). Not in FF or REW.

In my case i forget to connect the head output cable to the motherboard. Pressing the AMS -->| button the pinchroller pressed against capstan and stay like this. No ABS time obviously due to disconnected head.

Did you change the capacitors in RF amplifier? I have 3 decks with similar mechanism, all of them had leaking SMD capacitors inside RF Amp.
(there are 2x 22μf, 63v electrolytic SMD caps)
 
Interesting.

I think that it does not have to read ABS (as some earlier decks like the 1000ES do not record ABS time subcode), but maybe needs to read the ATF subcode (tracking).

It would be interesting to monitor the RF signal on the scope. Maybe a part is missing.

You could try to rotate the S1 left guide CCW (counter clockwise) of 1/4 turn, and check again (memorize the initial position).
 
But it does it only in AMS -->| (next track) for some reason...

AMS |<-- (prev track), FF and REW was unaffected, even with the head disconnected from the board.
 
hdrobien said:
Thanks but the video is private so I can not watch it.
Click to expand...
Re my issue are you able to watch the video?

I'm thinking to do a last test... swap the heads between my 55es and 75es. If the problem follows the head then i have a weak head and there is nothing more i can do.
If the problem follow the transport, then it's alignment issue.

What do you think? I'm risking to missalign my good 55es by doing that?
 
Looking at the video, It is not clear when the ATF is on (Long) or off (Standard).

As I never tried to visualize a standard tape in test mode (As I have tracking test tapes) I can't really say. But if the RF signal is stable with the ATF and unstable without, I would first try to adjust tracking.

Remember : in normal mode (test mode off), you should hear chopped sound while playing a tape in fast forward, without digital artifacts.
 
Good morning!

Video starts with ATF on
At 0:08 i switch it off, at 0:15 the deck turn off by itself the output (relay kick in)
At 0:25 i turn on the ATF again and output come back immediately.
Αat 0:33 i turn off again the ATF, output is turned off at 0:36
Αt 0:46 i turn again on the ATF and output come back.

As you say, RF is stable with ATF and unstable without...

When you say to adjust tracking you mean the tape path with S1 & T1 guides? or there is other procedure for the tracking?

Re playing a tape in fast forward in normal mode:
I can achieve this behavior (chopped sound without digital artifacts) but with a catch:
I must precisely adjust the S1 & T1 guides for the specific tape that is playing. New tape, new adjustment needed.

Sounds like it's normal but it's not, since all my other decks can play fine all tapes and i can hear the chopped sound while playing the tape in fast forward.

Looks like this one is very sensitive, there is no any margin for errors. If it's not perfectly aligned with the tape doesn't sound good...

I'm tempting now to brake the remote control (the only one i have) in order to access the stupid hidden button to check the head hours...
 
Hi

From my experience, only the RM-D55A and the RM-D757 have the hidden button.

About your tracking problem, I would start by re-adjusting the left guide S1, then the right one (T1).

Rotate S1 CW until the left part of the signal (on the scope) starts to shrink (disappear), then go back 1/8 turn.

Then adjust T1 until the signal is nicely shaped and chopped sound can be heard.
 
Yes i have a RM-D55A R/C. Need to find a non destructive way to open it, then i would like to find a way to capture the signal of the hidden button (with an arduino maybe).

The guides are already adjusted but maybe not this way (i start with T1, then go to S1).

I will try again as per your instructions and let you know.
 
Thank you SaSi for posting this. Some posts are timeless! I retrieved my DTC-690 from the attic last week and started to transfer my old DAT masters to the laptop. The 690 hadn't been used for 13 years, though I bought it new, er, in the last century. Recorded ten of 16 master tapes then it suddenly wouldn't eject (or play, FF/RW) a tape after I rewound it. Tried some other quick-solution posts, which didn't help, and then found your excellent post. I now have the tape back in its box and the tape-drive mechanism removed, and, after scoffing some food, will remove the casing--thanks for mentioning that screw which is only visible through the holes on the wheel! I hadn't noticed that. I can see that the problem is T1, which didn't move when turning the black cog. S1 and T1 were both wobbly, though a gentle push moved S1 yet the same pressure broke off T1 (tiny screw looks unsnapped, so I'm guessing it was just very loose). Remembering calibrating Otari 24-track ATRs, I'm concerned that S1 and T1 affect the azimuth, but I'll blub about that once the 690 is working again. Truly, I hope you are living long and prospering :) Thanks again for this very helpful post.
 
Hello.
I have a weird problem with the DTC-55ES.
When I press the record button, it goes straight to AD-DA or DA converter, the relay clicks and that's it.
Any idea what to check?
Thanks!
 
It looks like there is a problem with the rec enable switch, thus the deck switches to converter mode.

Check the switch and its continuity to the main board.
 
hdrobien said:
It looks like there is a problem with the rec enable switch, thus the deck switches to converter mode.

Check the switch and its continuity to the main board.
Click to expand...
S901-1 and S901-2 are both ok.
When I press them both, I get continuity on pins 6 and 7 from CN132. Checked continuity of pin 6 from CN132 and CN312 up to pin 50 on IC312 (REC ENABLE).
But, the devil is in the details :)
It was the Recognition Board PCB. One of the traces was broken.
Now I can record without a problem.
@hdrobien you have my thanks!

WhatsApp Image 2023-11-07 at 18.00.45_75b70b63.jpg
 
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