more midi2cv...

[Andrew Schrock]

(Ok. One more try to get this email through.. I tried twice this morning
and they just dissapeared.) 

In a nutshell, my midi2cv has been in for service twice and is still
somewhat ailing. I'm tired of bugging paia since it's spent so much time
there. Most of the time I'm able to puzzle things out, but this one has me
stumped. 

The midi2cv works ok, with one exception: it seems like the 8 ouputs bleed
into each other _far_ more than they should. The main area this is
noticible is the frequency c/v (in mono mode) which goes sharp when you
depress a key and then flat when you release. The output goes between .02
and .04 volts higher than it should, depending on how hard you press the
key. (definitely velocity bleeding in) I can hear the VCO it controls go
sharp then flat, and my DMM confirms this. Somehow the different outputs
are modulating each other. I don't have an oscilloscope so I can't really
see what's going on. 

I've tried different grounding schemes, I've even disconnected everything
except for _just_ the frequency c/v and ground and the problem still
exists. It's definitely internal to the PCB, and not a grounding issue. 

Any ideas? Replace the opamp buffers? Power supply? Help...? 

Andrew

-| Andrew Schrock | aschrock at cs.brandeis.edu |-