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Randall RG50-112 Distortion Channel intermittent then quit working

Started by LBeast, November 18, 2023, 05:55:32 PM

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That is one of the better pictures I have seen of the track side of a PCB, it really helps to see the shadow of the components through the board.
I often use a torch to shine through the board when I take the photo.
Would you be able to take some good clear shots of the component side, it helps to see where the tracks go to.

Perhaps you can open your 150 amp and see if the same link is on the bottom of that PCB ?
It seems to be the same amp basically and the PCB seems to be the same type.
If you do that then you might as well take the photos of that amp.
There are no stupid questions.
There are only stupid mistakes.


Sorry for the delayed response. Been battling Covid for the past couple of weeks. See if this component side pic will work.


I don't think that green wire under the PCB is at fault, they just relocated the wire from the relay to the Master Volume pot.
The wire goes from the relay to a point after the Gain Pot in the Distortion Channel.
It goes to a junction between a 1k resistor, JFET, 22pF capacitor (20pF).
I am still tracing it slowly for you.
There are no stupid questions.
There are only stupid mistakes.


This is what I have come up with from the pictures of your RG50-112 PCB.
I copied a picture of the tracks (mirrored) into KiCad, drew up the original schematic and made up the components.
I had to give the components names in KiCad so I made them up as I went. (Ie. R1, C1 etc)
I placed the components on the picture of the PCB tracks and drew the tracks in as close as I could.

I did find some differences compared to Randalls schematic so I changed my schematic to match what was on the PCB.

I think my version might be helpful for anyone who is trying to fault-find one of these amps as the components have names on the schematic and on the PCB drawing.

There are no stupid questions.
There are only stupid mistakes.