[sdiy] TR-909 dead tom

[Adam Inglis]

Prob not much help in your case, but I recall a tom disappearing in my  
909 a while back, and it returned after I cleaned up some gunk on the  
board around the DAC.
Yeah it's pretty tight to work on the switch board, easy for the voice  
board.
May have to rig up a separate 5 volt source so you can have it right  
out and exposed?

Adam
On 26/07/2014, at 9:49 AM, greg at gzifcak.net wrote:

> 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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