Deofol Whistle

Y

yanivt

Member
  • Project name
Deofol, Okko Diablo Plus

  • Description of the problem (What does it do? What does it not do?)
Pedal creates a loud high pitch whistle when engaged. Replaced the transistors and had the same result. The pitch of whistle changes when the gain/level knobs are turned but always exists. Q1 seems microphonic when knocked.
  • List any modifications/component substitutions
Zero mods. Used Siliconix J201 through hole from reputable source.

  • If applicable, did you hard-wire the 3PDT switch or use a Bypass Board?
Hand wired both switches.
 
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This fix seems to be working for everyone who has tried it.

Basically you need to:
  1. Disconnect lug 2 of the Gain pot from the PCB and insert a 39K resistor in series with the lug / PCB pad.
  2. Add a 10nF capacitor from the gate of Q3 to ground.
16
 
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hello, I've tried the fix as mentioned above. even though whistling disappears, to me it's not a way to go, since the tone color changes too much.

could someone please post target jfet voltages for this build.

any alternative fixes? bias trimmer?
 
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