Tascam 38 Sync Mode Level Drop Problem

[LivingRoomSounds]

Moved

PostPosted: Sat Jun 22, 2013 4:37 pm Post subject: Tascam 38 Sync mode level drop problem

Hi, I?m new here and I have read through many Tascam 38 threads already, but the issue with my 38 seems to be different. I would be very thankful for a suggestion on how to solve this problem.
I had it in a repair shop various times after the Input/Sync/Repro control died. I couldn?t select any of the 3 modes anymore, which meant there was nothing going in or out of my 38.
Since everything else worked fine I figured I would just need to get the Input/Sync/Repro control fixed. Since they changed it, it has never been the same.
I can?t exactly remember what they did to it, but I brought it back 3 times and after the last time they replaced the Input/Sync/Repro PCB.
It worked fine at first, but then the problem came to light:

The level drops heavily in Sync mode. When I switch to Repro the level is still low until after 5 seconds, when it slowly rises back to normal level.
This happens with all 8 tracks, so I doubt it?s every relay on each card.
When I switch from Input to Repro everything?s fine and the level is there instantly.
Whenever I switch from Repro to Sync or back, the level is almost gone and I also hear a clicking sound.
When I turn the machine on and off I hear a clicking sound, too, when it?s set on Sync. This clicking sound isn?t there when I turn it on and off in Input or Repro mode.
The other significant difference to other 38s is, that there is no blinking on the tracks when armed. If I want to record something in sync mode I have to set the level while actually recording or go on input mode. It has always been like that and worked fine, but I couldn?t find any info on this.
It?s been overhauled at Tascam Germany from the previous owner in the late 90s and it used to work great.
Any idea anybody?

Thanks in advance
Roman

[LivingRoomSounds]

I get a great playback in repro mode, but when I switch to sync mode the level on all 8 tracks drops drastically, maybe to 20%.
When I switch from sync back to repro it's still at 20%, but after 5 seconds it rises back to normal level.
When I switch from input to output the level is there, 100% right away.
It happens on all 8 tracks simultaniously, so this can't be a track pcb relay problem, right?

I was wondering, can anybody tell me if there's a difference between the output select pcb of the older 38s to the newer ones? I know the difference between the 2 in sync mode when it comes to arm a track/ punch in.
On the newer ones, when a track is armed, you are still hearing the recorded track until you hit record while on the older ones you hear your new signal when the track is armed. Could that possibly have anything to do with that? Is there a different wiring from the output select pcb?
Or is there another relay in there that could be a problem?

Sorry for my lack in technical knowledge. I'm just wondering if anybody has experienced anything similar.
Any leads are highly appreciated.

Thanks
Roman

[wkrbee]

There are transistors on the I/S/R PCB that switch relays on the R/P cards.Being all channels are affected, it points to the I/S/R pcb assy.You could have a leaky transistor or cap.On some of the older 38s the bracket that holds the pcb would short to a trace on the pcb when it is reassembled.That would explain the multiple returns to the shop.They may not have taken the effort to resolve,(test after reassembly), the problem.Take it back,or get your money back and take it to someone who will make the effort to fix it right.

[wkrbee]

And swapping out a PCB that has at best 10 components on it is a sign the shop doesn't know what's going on-and there is a difference between the older and newer version of the 38.

[LivingRoomSounds]

Thanks so much!
Funny thing is, after I left the machine on for about 36 hours the problem disappeared. But only for a minute, then it was right back there.
So a cap failure would make sense.
I also remember after getting it from the shop it always worked for a while until the problem reappeared.
This is one of the newer models, does that mean if they put in an old I/S/R pcb it could also be a problem with a short?

Yeah, that shop wasn't the right place for the Tascam. Unfortunately it's been too long to get my money back and I defenitely won't bring it back there.
But I have a friend who is able to help me with his technical skills.
We've been considering to take a closer look at the I/S/R pcb and the connections to the motherboard.
Thanks again!

[LivingRoomSounds]

So, we took out the "Out Select PCB" or "Selector PCB 104" as it says on it.
Now, I realized that the number on it is "5210075201", while on the manual it should be "5210075200". Could it be that the "...01" card is from a newer unit (s/n above 400 000) and causes problems cause my 38 (s/n 330 064) is an older unit and requires the "...00" card?
I cannot find any information about the actual difference between older and newer "Out Select PCB"s and wonder what it is...