Author Topic: Built 2 Danger Zones. 1 mostly metal film 1 mostly carbon. Totally different.  (Read 766 times)

Superstereosix

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Voltages around the chips are pretty much the same,(and close to readings in the pdf) but carbon one is giving me too much fuzz, almost octave like on the decay.  (Almost fuzz factory like if you know what I mean).
 I bypass the buffer and the tone still getting the same issue.  Something's going on around the 4049 I figure.. I don't think it would be the supply, probably one of the amplifier stages.. I think I'll see if I can signal trace through the stages.  All the resistors are carbon (these are older, I've had them since school) except R18.  Check and see if DC is blocked at C10 and C12..  Thinking of replacing the chip. 
Am I headed in the right direction?
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Superstereosix

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DC seems ok.  A bit low though on both circuits.  2.9 - 2.8V on most pins.  3.2V on pin4 of the metal film.  Bean's got his all up around 3.4 - 3.7V.
Haven't traced yet, but this could be it..
Hmm.  gotta 22ohm 1/2 watt in R5; the supply to the chip. All pins on the 4049 are on the low side of the pdf voltages..
I might have to change that to a 20 or so.. just tack something in parallel to bring it down some..

Might have to wait until tonight, got me some chores to do...
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blearyeyes

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Better if you post this in the Tech Help forum with pictures of the board etc. There is a sticky post with all the best ways to get help...
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m-Kresol

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I don't think that it has anything to do with carbon vs. metal film resistors in terms of material and mojo tone or whatever. It's more likely that there are differences in tolerances and thus more pronounced differences in resistances.
Have you double and triple checked your part values? it might just be that you've got a wrong resistor in there somewhere.
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