Blue Shoe Gai Pan trimmer bias

L

Lang1320

New member
Board has 3 trimmers. I need a High School shop class level explanation on how to set the bias trimmers, please. I understand the transistor inconsistency and thus the need for trimmers vs fixed resistors. Setting by ear is not an option. What voltage? Where do I connect the leads? 1/2 supply voltage and "typical" settings are not applicable. I'm looking for specific settings on a specific board.
 
Not sure if this is too late, but half supply voltage is applicable for trimming JFETs. Since the supply is 18V due to a charge pump, measure about 9V on each JFET Drain. Look up "J201 pinout" to find which pin is the drain. Hope that helps!
 
daveybee123 said:
Not sure if this is too late, but half supply voltage is applicable for trimming JFETs. Since the supply is 18V due to a charge pump, measure about 9V on each JFET Drain. Look up "J201 pinout" to find which pin is the drain. Hope that helps!
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Start with Q1 and go in order, some have suggested biasing a little hotter like 11v, set mine at 9v and sounds great
 
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