Revisiting the Abductor debug...

Started by Luke51411, July 21, 2015, 09:39:39 PM

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anotherjim

Ok, have you tried grounding out the input? A spare jack plug with ring/sleeve shorted together is handy for this, as it makes the power contact (assuming power neg is switched by the ring contact of the socket). Output should be dead silent, if the noise is still present, you can be more certain of an onboard problem. And, while the PT2399's are out, make sure all delay level controls except for output volume are at minimum - check that these controls really have their wipers to ground with a resistance measurement. IC5b is a mixer, so any noise on the output can be the sum of every bit of noise on each input to this mixer.
While you're resistance testing, make sure your input jack is well connected - plug your guitar lead in and test for low resistance from tip at the guitar end to the junction of R3/C5 - and from the sleeve to everything in the pedal that should be ground. Similarly, confirm from the output lead back to the volume control.




snap

That D1 post made me look at the PS section. Again a question for deadastronaut: no small cap across C3 (and C1, C4)? All the possible hash coming in from the 9V jack directly to the noninverting input of the first IC (and others).
Shunt named 3 electrolytics with 100n ceramics. Basta!