Help needed: Restoring an AIWA XD-S1100 DAT recorder

[BijanK]

Hello!

I am currently restoring an AIWA XD-S1100 DAT recorder. I am aware of the issues with the SMD components on the mechanism's board, but those issues have been solved. The board has been properly restored and runs fine. Voltages are all there. All other components of the device also seem to be pretty much brand new, except for the mechanism.

The mechanism has been degreased and fully lubed up again. However, the machine is suffering from the apparently well-known and widespread "CAUTION"-message issue that always appears 3 seconds after PLAY or REWIND/FORWARD have been engaged. There are several machines to be sold on the web that show this issue.

It has been suggested that this might be a tape tension issue, but I am still in the dark on this.

Does anyone with experience in servicing AIWA DAT recorders know how to resolve this issue? Or, if not, know how tape tension can be adjusted on this machine?

Many thanks!

 

[hdrobien]

I would suspect a problem with the reel rotation sensors (CP3 & CP4).

Does the counter "move" (normal mode, not ABS) during the "3 seconds" ?

 

[BijanK]

The counter seems to have 3 different modes: A.TIME, P.TIME and a simple 4-digit counter. You seem to mean the latter? I don’t see any kind of movement in any of these modes whenever I try to play or wind a tape. (To be honest, it’s less than 3 secs, unfortunately.)

A few other oddities I observed: whenever I press RENUMBER, ID.ERASE or any of the track calendar numbers, the mechanism will immediately enter REWIND and aggressively rewind into the tape end and then giving me “CAUTION” again. Curiously, the recorder also enters REWIND whenever a cassette is inserted and I press OPEN/CLOSE to eject it. As both reel and tray motors are handled by IC18 (driver), I was suspecting a fried IC. However, all other mechanism functions work fine.

I checked voltages on CP3 and CP4 and they’re all fine. I also cleaned the sensors with alcohol (but without entirely disassembling them), but no change. Now, of course, the photo diodes themselves could be broken, but I wouldn’t know how to reliably test them.

 

[hdrobien]

I would check signals on IC6 "System Control", pins 29 & 30, or on the collector of TR8 & TR9.

While rotating the reels, you should be able to monitor pulses 0-5 V DC.

 

[BijanK]

Thanks, that’s a great idea! I’ll try that this weekend and let you know.

 

[BijanK]

Thanks a lot, you might be on to something here. SFG (supply reel) measures correctly on TR8's collector, but TFG (take-up reel) measures only in the millivolts on TR9. On closer inspection, TR9 behaves somewhat strangely: all TR7 to TR10 measure correctly emitter-to-collector and base-to-collector (0.7 in diode mode), but while TR7, TR8 and TR10 give me 32 kilo ohms in resistance mode emitter-to-base, TR9 gives me a whopping 6 mega ohms. Now, does that indicate that TR9 is faulty? After all, there is some change when I measure voltages on TR9, but, as I said, only in the millivolts.

What do you think?

I might begin by revisiting all vias on the board that might have been damaged by SMD leakage. Maybe this is a voltage issue. After all, I noticed that the rewind issue I mentioned earlier when pressing OPEN/CLOSE seems to originate in the motor selection on the SYSTEM CONTROL IC: reel or tray motor selection is done through setting pin 13 (TRSEL) LOW or HIGH, so it would seem that this pin is staying LOW (reel motor) when it should be HIGH (tray motor) when pressing OPEN/CLOSE.

 

[hdrobien]

Checking vias and tracks continuity seems a good start.

 

[BijanK]

So, after much probing, it turns out the take-up reel sensor was indeed defective. That was only a symptom, though. The real culprit was a tiny, hard to see via in the vicinity of the TFG sensor that had been corroded. I rebuilt the via and the deck does run now (mostly). On to the next set of problems.

The deck does record, the level meter does show an input signal, starter IDs are written to the tape and the tape counter is running. However:

- If I rewind and check the recording, there is nothing. I do not hear any audio. Very occasionally, every few minutes or so, I do hear a brief speck of music. Thus, I think the recording itself is properly done. Also, starter IDs are read correctly.
- Recording only works through the analogue input, not the digital optical (could not test coax yet). If I connect a toslink cable and select the input, the level meters remain unresponsive.

As the recording works and some sound seems to end up on the tape, would this indicate a tracking/tape alignment issue that could be fixed through manual realignment? Is there a best-practice for this without a proper measurement tape?

Thanks a lot for your help!