TR-909 doesn't play cymbals...

[thejoerusso]

I'm helping someone out with 909 where things seem to work, except for hi hat and cymbals, the sounds which are sampled.

Before I dig in, any 909 gurus out there have similar problems? Strange that none of the three ROMS are working. ???

http://manuals.fdiskc.com/flat/Roland%20TR-909%20Service%20Manual.pdf

 

[peterc]

Check the individual outputs. If the sounds play out of there, but not out of the main outs, you have a dirty or faulty individual jack socket.

 

[thejoerusso]

Thanks Peter, but after looking with a scope, it seems that im not getting audio before the jacks. Actually i've got nothing at the common pin of the resistor pack after the ROM either. I've found one bad via on the hi hat trigger trace, but still no love.

 

[peterc]

Hmmm. I dont have schems, but is there a VCA before the output? I think there would be some kind of volume controller for level recall and programming. Could have something to do with that.

 

[thejoerusso]

Attached is the Hi Hat section, from the manual. So I've got no audio pre VCA... 

 

[peterc]

Is there a trigger, IC10 pin 7?

If there is, check the run/stop circuit works, IC72 pin3

Also check that there is output from the oscillator, IC72 pin4

Peter