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Oakley Chorus Distortion Problem
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author Oakley Chorus Distortion Problem
househead
Hi All, I finished my Oakley chorus a while back and was very pleased with the results, the next time I turned it on it started distorting in one channel ... I've recorded short video, hopefully you can hear the problem...

https://youtu.be/0i0tSdctMAs

Any light you could shed on this would be greatly appreciated
househead



Synthbuilder
It's horribly difficult to fault find without actually having the unit in front of me. Particularly with distortion problems. Right now, I can't say where the fault could be.

Check every IC has the correct power supply. So check for 0V (best done with the unit off and with a resistance/continuity tester) and +/15V (with it powered up and with a voltmeter). Use the schematic to see where the power pins are on each IC.

It'll be worth building yourself an audio probe:

http://diy-fever.com/misc/audio-probe/

These are actually useful even if you have a scope.

You should be able to trace the audio signal from start to finish as it moves through the SE330 with this probe. Found out where the audio goes bad. If it's distorting even when in fully dry mode (ie. no modulation at all) then it won't be a problem with either the companding circuit (V2164) or the BBDs (MN3207/MN3101).

Tony
Synthbuilder
One other thing: That case really needs a lid. On its own dust is not a major problem - but once moisture gets in there it'll mix with the dust to form a layer of partially conducting muck. Then you'll have problems like clock bleedthrough, unwanted noise and poor performance generally.

Use a soft paintbrush and a vacuum cleaner to clear the dust from the PCB. You should really use a special anti static brush and air duster but I don't think you'll have any problems using the ordinary household items.

Tony
househead
Some great advice regarding checking/testing and also some interesting points regarding the dust that wouldn't have crossed my mind to be honest..... I know it's hard to to diagnose a problem without the unit being in your workshop, thought it might have been something that's happened a few times with oter customers... As always thanks for your time and valuable advice brother Tony.

Cheers Tim
househead
Update: I'd put 620k resistors instead of 620r as well as missed a ceramic cap underneath an oversized poly cap....
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