Tacam 58 won't record on any channels

ethyrvalve

ethyrvalve

Norman Nanoweber
Hi all,
I was repairing some of those infamously dodgy rca connection on the mother pcb of a friend's 58-OB (incidentally this issue was exacerbated by the fact the machine had been dropped at one point and the RCAs bore much of the brunt) and that all went OK (but what a hellish job getting at that mother PCB!).
But once I got it all back together, the patient presented with a new, nastier disease:
None of its channels would record.
I verified the following:
1) Input as well as the sync and repro playback work OK on all channels
2) I verified that the erase function works correctly (so the master bias amp must still be functioning, right?)
Anyone have any ideas where to troubleshoot next? I have the full service manual and I also have my own, fully functioning 58 on hand to aid in troubleshooting.
Thanks in advance for any insights.
 
I have the same problem with my 48. It plays back previously recorded OK, but upon new record it is extremely faint across all 8 channels. So it's erasing and recording but barely!

I removed the two OSC boards and they look fine-no obvious signs of trouble. Re-installed and did a test record which worked for about 60 seconds and then degraded to miniscule audio!

So based upon Ethan's great comments, I have deduced that it's either- a) main OSC board issue or b) power supply issue or c) both.

I have removed the P/S and just ordered all new caps from Mouser. Once all caps are replaced and I have re-installed I'll try again.

If it persists the main OSC board will have to come out and be checked.
 
Hey Greg,
Thanks for sharing that.
I'm thinking in my case it isn't the main oscillator board because I have a working 58-OB at my disposal and I tried plugging its main oscillator board into the problem machine and there was no change. And I was also able to get the problem machine to erase using its own oscillator card.
This power supply thing is intriguing tho... Were you able to determine if your 48 erases OK?
There's a very small chance that this issue was caused by getting shook up in transit but it was only a few blocks and a couple staircases that it had to travel. It seems a lot more likely that my disassembling it to get at the mother PCB caused this.
 
It does erase and record but the record is barely audible!

So I was after recapping the P/S anyway and felt this was a good way to go to isolate that issue, and then I'll have a clean power source.

If not the problem then as Ethan suggested I'll have to check main board. It is very unlikely that both OSC cards would fail. So either is power or a bad main oscillator.

I hope it's a power issue but will not know until I receive the cap with the order I just placed with Mouser. So at least a week's wait.

Back track what you did and maybe you have a plug not fully seated.

Do you need a copy of S/M?
 
I do have a service manual, but it very kind of you to offer!
You're probably right that I have a plug not fully seated--those little pin and header things are the bane of my existence (I built an 1176 with a bunch of them without the proper crimp tool--they kept popping out of the housing).
Best of luck with that power supply recapping. I re-capped the power supply on my Studer b67mkII last year, and it turned out that the problem was actually just a loose jumper on a card. But I'm really glad I re-capped. I swear there was an audible improvement in the sound of the machine.
I can't remember who said this (someone on the groupdiy.com forum IIRC) but at the end of the day you're listening to your power supply.
 
Lytics age and get noisy. Huge problem in audio circuits and especially in loudspeaker crossovers.

Power supply caps take a beating over time and the heat does not help either. So replacements produce great results.

I am doing a ton of cap replacements on more than just P/S's. Redoing every sound card in my 42 and 48!
 
GCalo said:
Lytics age and get noisy. Huge problem in audio circuits and especially in loudspeaker crossovers.

Power supply caps take a beating over time and the heat does not help either. So replacements produce great results.

I am doing a ton of cap replacements on more than just P/S's. Redoing every sound card in my 42 and 48!
Click to expand...
I hope it goes swimmingly Greg!
For the record, cleaning the 'Function A' PCB (track arming) seems to have fixed the record issue on the 58. It was pretty gummy and grimy with years worth of tape particles.
 
What is the Function A PCB and where is it in manual?

I'll look that up to see if similar to 48.
 
Hi Greg,
The track arming switches (record enable/sync pre-load--maybe the remote switch too, I'm at work and I can't recall exactly) on the 58 are connected to two PCBs -- Function A on top and Function B on the bottom. I tried to make sense of the schematic and saw that the record signal was passing through the function A board.
 
GCalo said:
So what did you do then to correct your record problem?
Click to expand...

Strangely enough, cleaning the tape oxide pieces and gunk off that PCB seemed to fix it. (I had already tried re-seating all the pins and headers related the record function to no avail).
I don't discount the possibility that it could have been completely unrelated to the problem and that maybe I unwittingly got it working just by putting it back together for the umpteenth time.
 
So do I.

Went through whole unit yesterday and nothing seems out of line, and while that's no absolute at least there does not appear to be any visible evidence of a toasted part.
 
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