# Twin Face PNP Biasing



## JetFixxxer (Jun 7, 2020)

I went to check the biasing of my Twin Face with the trim pot fully CCW I can only get it to -5.35v.  Bad trim pot?


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## ferdinandstrat (Jun 10, 2020)

JetFixxxer said:


> I went to check the biasing of my Twin Face with the trim pot fully CCW I can only get it to -5.35v.  Bad trim pot?



Actually there's another option: You are most likely using PNP Germaniums right? Well they are incredibly sensitive to heat. It happened to me too, I built a PNP Germ Fuzz Face and suddenly it sounded splatty and....crap, checked the voltages, pot vaules, tried a 500K bias pot and nothing....turns out I had to throw the thing in the fridge cos it was middle of the summer


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## music6000 (Jun 10, 2020)

Did you change the toggle mode switch to the PNP side to adjust Bias.
Toggle switch feeds voltage seperately to each side!


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## JetFixxxer (Jun 11, 2020)

music6000 said:


> Did you change the toggle mode switch to the PNP side to adjust Bias.
> Toggle switch feeds voltage seperately to each side!



Yes I did.


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## Many__Of__Horror (Jul 15, 2020)

JetFixxxer said:


> Yes I did.


Did you end up figuring this out, I just built one and am finding the exact same thing. Though I seem to be getting no sound out of the PNP side so i have some more investigating to do.

EDIT: I had the PNP trannie in the wrong way with the base & collector swapped. Put them in the right way & the voltage is now correct & I get fuzz.


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## JetFixxxer (Jul 17, 2020)

Nope.


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## benny_profane (Jul 17, 2020)

What was the source of your transistors? Were they measured for gain/leakage?


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## JetFixxxer (Jul 18, 2020)

benny_profane said:


> What was the source of your transistors? Were they measured for gain/leakage?



I got them ebay about 8 years ago and they were in my original Fuzz Face Clone.  I don't remember leakage measurements.


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