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The pot for the filter res also control a VCA which counter acts the drop in audio level when the filters resonance increases. Sounds like the VCA is working just fine but for some reason the feedback res for you filter is not. Res CV control is pin 2 on the SSM 2044 filter chip. It may be socketed and could need a little push to make sure it is seated correctly or the chip might be at fault. Trimmer VR-3 adjusts the res and the only other component between that and the pin is R2 1.7k resistor. Check these are still OK. I’m pretty sure VR-2 Res pot is fine and VR-4 trimmer is all good as this is the trimmer for the VCA which we know is working.
As it’s something that happened from being in use of a while rather than it being worked on or moved around then I suspect your chip has gone bad but these can still be found at a reasonable price. If it’s socketed I would remove it and check with a scope what voltage I could see at the pin 2 socket point when adjusting the res pot. If nothing then there’s a problem with the trimmer VR-3 or R2. If there is a good CV there then it’s your chip.
Sent from Mail for Windows 10
From:
voltagegrove@... [korg_mono-poly]
Sent:
02 December 2015 05:57
To:
korg_mono-poly@yahoogroups.com
Subject:
[korg_mono-poly] Filter Resonance Not Working
Hey guys, delighted to tell you that my Mono/Poly is full healthy! For the time being that is... All voices are stable and in tune.
I had it powered on all day today, twiddling about to check over the parameters and what not. I had let it sit powered on for a few hours only to come back to it with the filter resonance not working. It only just increases the output level, basically just makes it louder. Regardless of settings, unison, poly, etc.
It was working great and then all of a sudden, no resonance, but it just increases the output level. The rest of the filter works fine. Very strange...
Does anyone have any thoughts or ideas of what this could be caused from
I was so happy to have it back after its three month stay with my tech, only now to have another issue...
Any thoughts, hints, tips or tricks would be much appreciated...