Tascam 34 - meters doing strange things

R

rob aylestone

Moderator
I've looked at the schematics but his fault seems to make little sense.

Meters work fine on input monitoring, but sync or replay produces zero output on the meters - the actual function works fine, but the meters just zero when you switch from input? I've not found anyone mention this as a fault anywhere, so figured I'd ask the clever folk here.
 
34 or 34B? Probably irrelevant but just in case it matters…

And just to confirm, it’s global across all meters, and it doesn’t matter if channels are in sync or repro? The simple fact is there is no meter activity unless the source mode is in input?
 
Sorry, a 34B. Lets say you have level on all 4 channels. You hit record and it starts to record, but try to monitor off tape and the meters go dead. Rewind and replay reveals the recording happened, but no meters working. Very odd. I didn't do anything?
 
I’ll have to see if I can find the schematics for the 34B. Unless you have them? I’d start at the global mode switching circuitry since it is a global issue. But I’d need to have schematics to advise further.
 
I'm sure I have it in the office somewhere - I'll try to find it. I had a serious tidy up and can't find anything now!! I think it was for the 34, not the 34B I have.
 
I got hold of the full operation/maintenance manual for the 34B.

So just to be sure I understand what you are saying and doing, you have the OUTPUT SELECT switchrack set to INPUT, you adjust your levels on the four input channels, put the transport into REC/PLAY with all tracks armed to record, you still have VU meter activity because you are monitoring the INPUT still, but when you switch the OUTPUT SELECT switchrack to REPRO the meters go dead while still recording? And when you rewind and playback with the OUTPUT SELECT switchrack still set to REPRO you have proper print to tape on all four tracks but there is still no meter activity?
 
Try reseating connector J180; a white 5-pin connector that plugs into P180 on the motherboard and goes to the OUTPUT SELECT PCB.
 
Just a guess? A relay not dropping in or out? If Tascam do signal routing with FETS or transistors these often gave problems in all sorts of vintage gear. Odd because 'muting' transistors are not stressed and have FA to do really!

Also, if transistor control a +ve or -ve supply might have gone AWOL. IF you find a schematic Rob, may we see it?

On another front: I am feeling much better these days (but diuretics are a B nuisance!) and I will have to gird my loins and tackle the BOsc problem with my A3440 soon. The fashion for analogue tape can surely not last much longer?

Dave.
 
Yeah that was my line of thinking, Dave…because Rob’s issue is global I took a look at the global OUTPUT SELECT circuitry. It looks like the INPUT mode is different than SYNC or OUTPUT…the latter two when engaged ground switching FETs to a common ground rail to change the source path for the meters along with the audio. And that rail connects to the system through one pin of the connector I mentioned for the meters…there is a separate connector for the audio. If that connection was compromised I think, if I’m understanding the circuit correctly, it would elicit the symptoms Rob is describing. So, maybe even manipulating that connector during SYNC or OUTPUT mode operations might show some intermittent meter activity and if so affirm a compromised connection of some sort; oxidized contacts, bad solder joint, etc.
 
I will confirm this as soon as I can, but I'm a bit stacked out at the mo - next week should be fine! I really appreciate the guidance here guys!
 
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