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DIY Stompboxes => Building your own stompbox => Topic started by: tonedawg on November 26, 2021, 05:42:45 PM

Title: What are these?!
Post by: tonedawg on November 26, 2021, 05:42:45 PM
Can anyone identify these little junctions on this board? Just wondering about their function.

(https://i.postimg.cc/mP8rNwZY/IMG-8450.jpg) (https://postimg.cc/mP8rNwZY)

(https://i.postimg.cc/XZqY2CXT/IMG-8451.jpg) (https://postimg.cc/XZqY2CXT)
Title: Re: What are these?!
Post by: theehman on November 26, 2021, 05:47:32 PM
Maybe test points that you can put your meter lead tip into while you make adjustments?
Title: Re: What are these?!
Post by: iainpunk on November 26, 2021, 05:54:54 PM
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
Title: Re: What are these?!
Post by: tonedawg on November 26, 2021, 06:23:49 PM
This is actually a Trueman 1966 fuzz I am tracing. First time I've ever seen trimmers like that.
Title: Re: What are these?!
Post by: iainpunk on November 26, 2021, 06:58:27 PM
isn't it just a fuzz face without a gain control?

those trimmers bias the transistors.

cheers
Title: Re: What are these?!
Post by: tonedawg on November 26, 2021, 07:39:19 PM
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.
Title: Re: What are these?!
Post by: Rob Strand on November 26, 2021, 08:07:05 PM
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.