Tascam 34 Repro Out Issues

LUNE

LUNE

...a pieds joints
Hello fellow Analog enthusiasts,
I’m new here to HR forum and signed up especially for the Analog corner over here relating to Reel to Reels - I’ve already mined some great info just eavesdropping. I’m also new to Reel to Reels, having (unfortunately, as I now see it) jumped right into Tascam DA88s from my cassette machines when digital came around. …Well, better later than never…
I’ve picked up a few stray orphan machines in the last month (Tascam 34 & 38) and got the 38 running after a belt change and rerubbered pinch roller, however the 34 still has some issues.

At first it would only record on channel 1 and would register input only on 1 & 3. It seemed to record a week signal on 4 even though it wouldn’t register an input on the meter. I sleuthed out the main problems working from the inputs to the channel boards and they cleared up with a good cleaning of the “mother assembly board” (the board where all the channel boards plugs into) with isopropyl and deoxit.

So, now I have a functioning machine that will record on all 4 tracks and play back on the sync head however there is no playback on the repro head on channels 2 & 3. Being channels 2 & 3 makes me guess it’s not an alignment issue (plus there is NO signal whatever coming out of the channel) – I’ve switched out the channel strips, but the problem stays on channels 2 & 3 which makes me guess it could not be an issue with the channel cards themselves.
It could still be an issue somewhere on the “mother assy board” or somewhere after the repro head, …or?
Anyone have any suggestions where I ought to be looking?

I’ve had some good learning even thus far with these Tascam machines – I’m no electronic repair guy, but these are great fun to learn on and it’s nice to have a few machines with similar designs to compare.
Tape path & heads are cleaned & demagged. Fuses measure good. I’ve got a maintenance manual for the 38. I’ve got a cheap multimeter, and I’ve definitely got the obsession.

Any ideas appreciated.

Cheers,
-LUNE
 
Welcome! I'm sure people will chime in but I was wondering if you checked the head harness to make sure all the connections are good and solid? I had an issue with my 38 on channel 5 when I first bought it last year and the (at the time tech) told me that I had a broken wire near the head harness. Good luck and don't give up. I hope this helps.
 
Thanks for the welcome and encouragement!
The solder joints at the head look good - i gave them a gentle wiggle in playback with no response. just now i measured continuity between the head and the end of the line that runs into the channel board's 'motherboard', which takes me back to the 'motherboard'. So I guess I'll be pulling out the channel card/motherboard chassis again to have a look.
is it possible that something is wrong with these individual channels on the head? some kind of internal corrosion? I'm wondering if there is some way to check if signal is coming off the head to rule this out, (or perhaps this would be risky with charging the heads somehow?) but I'll be sleuthing the motherboard again first.
Thanks!
-LUNE
 
Fixed (?) yet mysteriously so...

ok, so, for the conclusion (hopefully) on this story, I tested connectivity and found the bad connections on the 'motherboard'. I had previously well cleaned this and so I didn't jump on the de-oxit right off this time, but made my multimeter connectivity tests to find precisely where the the weak link was.

The 'mysterious' (to me) part is that the connectivity seemed to repair itself upon being thoroughly tested - it was in a section that went from top to bottom so it was crossing through the board I tested all the little sections one by one and they individually were working, and then in the end the whole section was passing current top to bottom. i put it all back together and have signal out of the repro head - I DID NO CLEANING THIS TIME AROUND, BUT MY PROBLEM SEEMS TO HAVE BEEN FIXED BY MERELY TESTING THE CONNECTIVITY. And this on two separate places - in fact I had a similar experience on some of the inputs on the motherboard, but because I was cleaning it just then, I presumed that it was the de-oxit working and not my electronic testing.

This to me seems rather mysterious, and (having little electronic experience and not having had this experience before) I guess I would not necessarily believe someone else telling me a story like this (thinking they had changed something else without noticing...). Maybe this is common on bad solder joints? (anyone have experience on this? should I be resoldering these joints to avoid problems in future?) and maybe my problem is not fixed forever but could come back if the temperature changes or something... only time will tell. I'll be using this deck as a multistage tape delay, so we'll see how it goes.

I can not help but think some Shrodinger's Cat / Quantum Mechanics style irony... My repro heads are working because I tested to see if they were working...
Or maybe that the electronics here just had a neurotic sleep - they just needed to be woken up with a bit of attention, just to know someone still cares about them... ...or, of course a rational thought would be that the joint is exposed to some small current when being tested and so a dead joint could revive connectivity somehow this way (and maybe only temporarily) - I think its interesting to note the suggestion I've seem with regard to revivifying crackly faders to work the fader back and forth WITH SOUND PASSING THROUGH. so Maybe this is all quite mundane to someone with more experience.
whatever, it does give me a little bit more of the feeling that our electronic friends really are ALIVE and maybe we are even somehow objectively justified with all our anthropomorphism. (they need our love...)

hope this story helps someone.
If anyone has some other reflections on this i'd be interested to hear - or if anyone suggests I resolder the joints - would it only be necessary to heat up the joints?
unless they start crapping out I'm going to leave it as is.
 
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