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What are these?!

Started by tonedawg, November 26, 2021, 05:42:45 PM

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tonedawg

Can anyone identify these little junctions on this board? Just wondering about their function.





theehman

Maybe test points that you can put your meter lead tip into while you make adjustments?
Ron Neely II
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iainpunk

they are trim-pots (trimmers), probably for bias or similar applications. what kind of board is that, thats something that helps us find out the function of those trimmers.

cheers
friendly reminder: all holes are positive and have negative weight, despite not being there.

cheers

tonedawg

This is actually a Trueman 1966 fuzz I am tracing. First time I've ever seen trimmers like that.

iainpunk

isn't it just a fuzz face without a gain control?

those trimmers bias the transistors.

cheers
friendly reminder: all holes are positive and have negative weight, despite not being there.

cheers

tonedawg

The configuration is a little more complicated as there seems to be two of these trimmers on either side of the bias knob which seems a bit odd. The bias pot is a 500k and also seems to be going to Q1's collector and Q2's base. The third trimmer seems to be going to a portion of the bass boost circuit which is one a switch but I'm having trouble understanding the tracing there since there's multiple resistors in series. I going to have to study a bit more to try and make sense of all of it.

Rob Strand

QuoteThe configuration is a little more complicated as there seems to be two of these trimmers on either side of the bias knob which seems a bit odd. T
They  would be used to set the min and max points so it sounds good/correct over the whole range of the pot.
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According to the water analogy of electricity, transistor leakage is caused by holes.