[sdiy] TR-909 repair Q

[Dave Magnuson]

The gate input on my analog kick used to do that...  There was a cap near
the input that would build up a charge after a few minutes.  It would then
stop working until the cap discharged... perhaps there's a cap on the
trigger for the snare's envelope generator that's holding a charge?  I put
a large resistor (can't remember if it was 470K or 1M) across the cap, and
it took care of the problem... it was enough to drain the cap between gates.

You probably won't need to add a resistor (used to work before)... maybe
there's a cap that's gone way out of spec

Dave



At 04:44 PM 5/9/02 -0700, Jim Johnson wrote:
>Well, the "dirt cheap" 909 I got a few months back has not been the
>blessing I thought it would be :'(. There were a couple of problems with
>it, and rather than muck with it myself, I decide to take it to a local
>tech. He solved one problem, but has been hung up on the other, which is:
>
>The snare's "crack" sound is intermittently inaudible. What happens is
>that, when it's first powered up, the snare works fine, but after some time
>- five minutes, an hour, whatever - the "crack" slowly fades away to
>nothing.
>
>Clearly it's something in the snare's VCO.. but what? The guy has been
>trying to isolate it with heat and cold, but so far no luck - once it goes
>away, it stays away. 
>
>Hoping that someone else has run into the same problem, and solved it.  
>
>
>Jim Johnson 
>Metaphoric Software
>-------------------
>Makers of Techno Toys
>Software for Electronic Music
>http://www.technotoys.com
>info at technotoys.com
>
>

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