[sdiy] TR-909 dead tom

[greg at gzifcak.net]

Hi guys,
Just joining the list again after a few years away. I'm working on my 909
and kind of stumped by my dead low tom.

I've determined that it's not the voice circuitry since I can trigger it
from the trigger lines of the other sounds. I've verified the trigger line
connection between the voicing board and switch board, and from the
connector back to IC604 and the other ICs to which it should connect. At
this point I'm not sure where else to look except to try every other
connection on the switch board. My only other thought is to drag out my
scope and look at the trigger lines, but it's tough to power the switch
board and still have enough room to probe around.

Can anyone offer any insight into the workings of the switch board so I
can narrow down my hunting?

service manual here if you need it:
http://www.gzifcak.net/TR-909_SERVICE_NOTES.pdf

Thanks in advance,
Greg