Gristleizer misery

Forum dedicated to helping people debug and troubleshoot non-functional pedals or builds. Please use an clear and informative title, indicating circuit and basic problem. Don't forget to mark the issue as fixed if this is the case.
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simmo
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Post by simmo »

Hi, I've recently built a Fuzz dog Gristleizer. Well actually I've built two. The first I got it working perfectly but I went for circuit board mounted pots which was not recommended. So when I went to mount it all in the enclosure it was difficult to fit. So in de-soldering the pots I wrecked the board. I’m now on to a second kit which works but has a annoying high pitched squeal I can’t remove. So all round misery here. I note Fuzzdog say, ‘Please do not attempt this build unless you're confident in your building and troubleshooting abilities. We cannot offer any support with this kit.’ As this was my first kit I should have listened. Still as a learning experience be it very expensive it was er...useful. So I would appreciate any thoughts as to what this squeal might be. I've put a perhaps not so helpful video of my Gristleizer on my youtube channel.

Thanks

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The G
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Post by The G »

You may have noticed that the lack of any context (schematic, version, build specifics, etc.) prevented your post from receiving answers. Squealing is usually a sign of positive feedback. Does it squeal the same when unboxed?

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simmo
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Post by simmo »

Sorry this is my first post , as with my making of this pedal I have not been reading the instructions properly. The schematic is on the fuzzdog site http://pedalparts.co.uk/docs/Gristleiser.pdf But hearing that squealing is usually a sign of positive feedback is a useful start for me to explore. And yes it squeal outside the box. My first pedal also squealed not at first but after I had wrecked the board de-soldering the pots.

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The G
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Post by The G »

First check: you should've used a 7660S (notice the suffix) and the pin 1 should be connected to V+. Otherwise, the charge pump's oscillation frequency will be in the audio range.

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