Tascam TSR-8 Takeup Problem

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kduncan99

New member
I got a TSR-8 from ebay (my second one), and the capstan belt was slippy. So I ordered a new one, and just now replaced it, and that seems to be going well. However, the takeup is acting weird. FF and REW are fine, capstan/pinch is fine, but when I go into play mode, the takeup reel starts to turn, then just stops and the tape spills to the floor.

Can anyone point me to troubleshooting steps for this symptom? TIA...
 
That is extremely weird. The TSR-8 does actually have a DUMP mode, but it's not normally accessible. You didn't touch anything on the capstan servo board, by any chance? That seems to have something feeding into (or from) the _DUMP line on the processor, but I'm not sure what. I'll look at the schematics in more detail later.
 
jpmorris said:
That is extremely weird. The TSR-8 does actually have a DUMP mode, but it's not normally accessible. You didn't touch anything on the capstan servo board, by any chance? That seems to have something feeding into (or from) the _DUMP line on the processor, but I'm not sure what. I'll look at the schematics in more detail later.
Click to expand...

Not that I recall - I've been pretty careful handling this thing. EDIT mode works fine, but that's not much help. :-(
 
kduncan99 said:
Not that I recall - I've been pretty careful handling this thing. EDIT mode works fine, but that's not much help. :-(
Click to expand...

***EDIT*** - See the following post, it may be as simple as a stuck EDIT button on the front panel. If not, read on.


OK, so as far as I can tell, the _DUMP line is a signal coming out of the processor, not going in. It does two things: disable the right reel motor, and also sends M-STOP to the capstan servo - presumably telling it to keep the motor running even though the right-hand tension arm has gone slack.

Assuming the machine really has gone into Dump mode, it either means that something is accidentally pulling the _DUMP line low, e.g. a piece of something has shorted it to ground, or else the CPU is deliberately pulling it low for reasons we don't understand.

Are all the controls on the command panel working, e.g. RTZ, LOC1 etc? If so, that would probably rule out a phantom keypress from the control panel. I'm assuming you've turned the machine off and on again just in case it's a transient fault?

If it were me, I'd first verify that it's not something mechanical like the brake drum seizing up - if the capstan motor is still turning while the tape is being dumped, it's probably a good indicator that it's somehow got into Dump mode because the right-hand tension arm going slack usually shuts off the capstan. Running the machine with the front panel off may help too, so you can see what the brake mechanism is doing.

If that doesn't yield further clues, I would take the back off the machine, flip down the control board (remove the 3 screws at the top) and have a close look around the big chip, U9 just in case something has shorted out pin 30. U17 and U29 are also implicated.
It might be worth reassembling the machine afterwards and testing it again, since if it really was a piece of metal swarf the act of inspecting the control board will likely have moved it elsewhere.

After that, I would get worried because we'd be going into "Find out what the logic levels is on pin 30 of the CPU" territory and that would be bad.
 
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OK, I have made a bit of an error - there are some weird inaccessible modes on the TSR-8 (e.g. Spooling mode), but Dump isn't one of them. It's a hidden function documented in the manual.

If you press EDIT and PLAY simultaneously, the deck will do exactly as you describe, with the right reel stopped and the tape spilling continually until you press STOP. The EDIT button should be lit in this situation. Is that the case? If so, it might be that something has jammed the EDIT button down internally.

If not, we may be still be looking at the machine going into Dump mode for no reason.

EDIT: Another thing to try - when the deck is in FF or REW mode, are the lifters pulling the tape away from the heads or is it scrubbing (i.e. you can hear the audio during fast wind)? If so, that would imply the EDIT button has been stuck on somehow.
 
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Update:

Edit and dump work as they should.
If you let the right tenion arm down, it stops the machine (and the capstan stops).
The brake solenoid and bands are doing what they should.
The lifters are working properly.
(I'm doing all this with the front panel off).
... ongoing...
 
kduncan99 said:
Update:
Edit and dump work as they should.
If you let the right tenion arm down, it stops the machine (and the capstan stops).
The brake solenoid and bands are doing what they should.
The lifters are working properly.
(I'm doing all this with the front panel off).
... ongoing...
Click to expand...

Right. So is the machine still spilling tape in Play mode, or is it now working correctly?
Just to double-check, when tape spill occurs, does it stop as soon as the right tension arm goes slack, or continue? My assumption that it was doing a tape dump is based on the notion of it doing so continually - if it's only spilling enough to switch out of play mode, that might be a problem of back-tension on the right-hand reel.

At this point it would be worth posting a video of it malfunctioning, assuming it still is. IIRC you will need to have 5 posts on the forum before you can post a URL.
 
Nothing seems amiss with the control board. Still being weird - what is very strange is that the takeup actually does spin for a second, then slows to a stop. I wonder if there's a bad capacitor somewhere. <sigh>.
 
sry - yeah, still messed up, and it stops as soon as the tension arm goes slack. is the back-tension one of those things that is very fussy to adjust?
re posting video... hmmm, let me figure something out. I don't have an account for youtube, but I do have a facebook account.
 
kduncan99 said:
sry - yeah, still messed up, and it stops as soon as the tension arm goes slack. is the back-tension one of those things that is very fussy to adjust?
re posting video... hmmm, let me figure something out. I don't have an account for youtube, but I do have a facebook account.
Click to expand...

Supposedly. I've never needed to do this on mine. You'd have to take the back off the machine, and have the control board flipped out so you can get at R103 and R104, which control back-tension (L reel) and takeup tension (R reel) respectively, and adjust them while the machine is running. You will need a non-conductive screwdriver or adjustment tool, or you'll risk killing the deck completely. The books say that you need a tentelometer to do this. If I was stuck with the machine otherwise useless I might be tempted to give it a try, however. If you can find a service engineer and ask them to set up the playback tension that might be best.

It did occur to me that there might be an issue with one of the tension sensor coils, but that would mean that it despools in FF or REW modes as well.
 
I second posting a video.
[MENTION=31942]jpmorris[/MENTION] thanks for your expert help with this.

Tensions do require a Tentelometer to set. I have one, but I do not loan it out. If you happen to be located reasonably close I might be able to help. Feel free to PM me if you want to share general info about your location if it looks like this may be related to takeup tension setting. I will say though it would really have to be out of whack to cause the problem described if I’m understanding correctly.
 
It appears R106 is damaged. The black cap which presumably is connected to the rotor, and allows a screwdriver to turn it, is missing/broken/something. I have no idea if the resistor is functioning, but it is a good bet it is doing something wrong. What does 106 control?
 
Hmm, I thought I hit reply. So I re-visited the circuit board. R106 looks like it got damaged - the black plastic top which should be attached to the rotor is missing, and possibly the whole thing is not functioning. What does R106 do?
 
kduncan99 said:
Hmm, I thought I hit reply. So I re-visited the circuit board. R106 looks like it got damaged - the black plastic top which should be attached to the rotor is missing, and possibly the whole thing is not functioning. What does R106 do?
Click to expand...

R106 is REW back tension - so it should in theory affect the torque of the right motor, but only in fast rewind mode (probably fast forward as well, I don't know). The test involves holding the left reel in place while the machine is in Rewind, and measuring the tape tension between the capstan and the guide roller on the right with a tentelometer.

The total list of tension adjustments is:
R101 - EDIT back tension
R102 - EDIT takeup tension
R103 - PLAY back tension
R104 - PLAY takeup tension
R105 - FF back tension
R106 - REW back tension

...but I would be very wary of adjusting them without the proper tooling.
 
I think I'm going to go back to the 1st machine and try to get it running for now. I'll leave this for another day. Thank you both for your help, I appreciate it very much!
 
That is really weird. I'll have to look at the schematics again when I get home. Clearly the right reel motor is working, and it's even maintaining tension correctly in EDIT mode. But for whatever reason it's not operating in PLAY mode. It rules out the Dump theory, though.
I'm not sure we can rule out tension 100% since PLAY has dedicated tension trimmers, but it would have to be a total failure, e.g. the trimmer has gone short or open-circuit.
When I get home I'll look at the logic path from the PLAY pin on the CPU, and try and figure out where it differs from EDIT etc. It might be a failed op-amp or something.
 
I wonder... The right tensioner has two opto-detectors. The one on the bottom is on-off, and the one on top is graduated (the bit of plastic or metal which blocks the beam is shaped such that it blocks more of the beam as the arm gets progressively higher). We've been presuming the tension mechanisms are all okay because the machine shuts down when the arm drops. What if the on-off detector is working, but the graduated one isn't? Would that produce this symptom?

---------- Update ----------

BTW - do you have an electronic copy of the schematics? That would be a groove...
 
The reason I’m going with “not a tension issue” is the takeup motor jumps. If it was a tension issue it wouldn’t move at all. If it won’t go when there is no load (the tape is slack), it certainly wouldn’t move at the beginning when it is overcoming static forces, tension arm load, etc.
 
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