Filter only worked a year. Than wobbeled into silence

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VerreyckenGerd
 
Posts: 13
Joined: Tue Feb 28, 2012 12:30 pm

Filter only worked a year. Than wobbeled into silence

Post by VerreyckenGerd »

Hi all,

I have a problem with my x0xsh0p kit.
I built it a few years ago. It has worked perfectly the first weeks. After that the filter was unstable. Like a random signal was modulating it towards completely low passing the signal into complete silence. At the moment only the ENV and ACC modulation "plops" are audible. These plops are changing when tweaking the Cutoff, Reso, Mod, Decay and Accent. So I guess the 4066 IC is OK.
Bypassing the VCO directly into the VCA gives me the sound you would expect from a filter less synth.

I triple checked for bad contacts already. Shaking every single component while playing the sequencer doesn't do the trick. However touching some components "electrically" on the filter section seems to briefly activate the filter again.

The x0x did always sound a bit agressive compared to others.when it worked.

I checked every resistor value of the filter.

I socketed and replaced q22 by a pair of 377s, no difference

I allready replaced some caps I could not measure on the cirquit. But not all.

Could it be that the filter is OK but being modulated beyond its working limits?
Does anyone know how can I voltage control the filter manually with a lab PSU?

Any other tips or probing tests to do are very welcome.

Kind Regards,

Gerd

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antto
 
Posts: 1636
Joined: Thu Apr 15, 2010 3:21 pm

Re: Filter only worked a year. Than wobbeled into silence

Post by antto »

what's your voltage at R46?

VerreyckenGerd
 
Posts: 13
Joined: Tue Feb 28, 2012 12:30 pm

Re: Filter only worked a year. Than wobbeled into silence

Post by VerreyckenGerd »

3,27v on each side

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