[sdiy] TR-909 dead tom

[greg at gzifcak.net]

Cool, thanks for the suggestions. I've got consistent continuity between
the connector and the inputs to the 4174s, so I don't think that's it. I
should go back and check the outputs of each of those chips though.

I know it's not on the sequencer input side either because I can see the
leds lit up for the low tom track, so my deduction is that the pattern is
stored, it's just not reaching the voice board.

>
> On 26/07/2014, at 9:52 AM, greg at gzifcak.net wrote:
>
>> 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.
>
>
> IC 1 is right at the corner of the voice board. Check the area
> carefully for a hairline, because 909 boards have been known to crack
> at the mounts on the corners when dropped, causing all sorts of lovely
> madness.
>
>
>
>
>
>>
>>> 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
>>>
>>> _______________________________________________
>>> Synth-diy mailing list
>>> Synth-diy at dropmix.xs4all.nl
>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>>
>>
>>
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>
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