Tascam M3700 " My Grp Buss 3 has a flat tire"

[garryn]

Hi All,
I have been a Tech for many years but sometimes you hit thoes Dog Repairs. You know the ones that you just can't seem to find the problem. I picked up a fairly clean Tascam M-3700 and I decided to go over it. There were a half a dozen problems that I have already resolved but the one I can't seem to find is; Group #3 is dead. My question is to experenced Techs out there in Tascam land. How would you go about your search?
I have buzzed out alot of wires and I just don't find any breaks. From the Group output there is nothing when I inject a sine wave to an input. To verify the meter bridge I just swaped a channel and #3 LEDS work fine.

Any ideas are appreciated, please keep them positive.
Thanks

 

[garryn]

Manual / Service is on me.
Download > Tascam M3700 Manual_Service

 

[GlennM]

In my experience, switches are more prone to fail than a circuit. If two fail together, it may be a devil of a problem to sort out

 

[garryn]

Yahoo just found the problem . Two pins were bent and shorted on the Buss 3 fader.
All good now !