[sdiy] TR-909 dead tom

[greg at gzifcak.net]

I forgot to mention, I've also verified that there is no trigger signal
coming out of the 4174 (IC1) on the voicing board at the pin for the low
tom.

> 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
>
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