[sdiy] Oberheim Xpander Res fail

[Gordon JC Pearce]

On Mon, 9 Jan 2012 15:12:41 +0100
Csaba Zvekan <czvekan at gmail.com> wrote:

> Hi Group ,
> 
> My Oberheim Expander fails to tune the resonance section but it doesn't tell me what voice. If I force pass it then the synth works just like expected. Even the percussive patches with high resonance work excellent .
> I'd like to look at some schematics in particular the auto tune feature perhaps some 4xxx CMOS is bad or something. Any suggestions ?
> 

My favourite for that sort of weirdness is 405[123] multiplexers.  See if you can find one that muxes the filter outputs back to an ADC or comparator of some sort.

-- 
Gordon JC Pearce MM0YEQ <gordonjcp at gjcp.net>