[sdiy] TR-909 mod Q

[Jim Johnson]

In trying to fix my TR-909's snare problems, I've come across what looks
like an earlier mod, and I'm suspicious.

The problem is that the tone portion of the snare drum is usually missing;
sometimes it is present right after power-up, but fades away a few seconds
or minutes later.

Here's what I've found: the VCO trigger line - the pulse that feeds the two
VCO's - is not changing state as I believe it should. In looking at this
circuit, I find that someone has scraped off the insulation on the trace
that goes just past R242, and there is a blob of solder there. That blob
might be intended to form a bridge to R242 - that's all that's nearby. In
addition, this trace has been cut a little later on - right beside the
jumper beside C66. I suspect that this blob might be making intermittent
contact to R242.. but should it be removed, or changed to give better
contact?

Does this mod sound familiar to anyone? I found a list of factory hardware
changes at http://hardware.freepage.de/raf909/, but none that mention
cutting a trace.

TIA - 



Jim Johnson 
Metaphoric Software
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