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Hi all, I am a proud and very satisfied 3 year owner of a Trinity18 watt plexi TMB build. This amp is amazing and his pretty much been my main amp ever since I built it It was my first build of an amp of any type. I was very proud of the results and Stephen was very helpful and I could not have completed the build without his kit instructions and help via email. If your considering one of these amps I would not hesitate. They are the real thing. I am a total tone freak, very picky about what I play and the quality of everything. Well I used to be. Now I'm laid back and just play. I love this amp.

However, when I originally built the amp, ch1 was not working. The only problem I could troubleshoot was that the vol pot for ch1 read 0.. I figured it was a bad pot to begin with since I made the mistake of not double checking the pot values with a meter before putting them in place. I was so happy to get the amp working that I just left things as they were and have been satisfied with the 2nd channel all this time. I really should fix ch1 though. Again, being a novice, only building a few pedals prior to this kit, I felt very nervous about going in and unsoldering all the parts wires to the ch1 pot. There is a lot going on there, and I was meticulously careful in putting it all together. Again, I assumed that the pot is bad. I just didn't have the heart to undo anything.

However, I was looking over some old notes and I found a remark suggesting that the pot may be ok but just shorted.

I have not really been inside this amp in 3 years. I have only had to change the EL84's once. I used a set of Holland NOS tubes for about 2 years and now I am getting by on a pair of cheaper new stock tubes.

Can you guys give me some tips on how to go about trouble shooting the pot. I guess I need to determine a shorted pot verses a bad pot? I need to familiarize myself with the circuit again so I have some homework to do. Please give me any help or suggestions you have.

Thank-you.

Fuzzylogic

Which channel are you referring to the TMB or the "normal" channel. Also are you sure it's a pot problem? Have you trouble shot the affected channel? If you think it's the pot itself you can measure across the 1+3 lugs of the pot and check the resistance. On a lot of instances other components in the circuit will be in parallel with the pot so you need to take that into the equation. Have a look in the resource section under plexi 18 watt and look at the schematic and let us know which pot you are concerned about VR1, VR7 or VR3.

The channel that does not work is the normal channel. When I measure the resistance of VR1. When I measure the resistance between 1 and 3 lugs I get a value of 0. The other pots measure out at there proper values. As far as troubleshooting the normal channel, all I did was make sure everything was connected correctly and that I had continuity. Outside of that I am not really sure what to check. Please let me know what you think, I have plenty of pics too.

Thanks,

Jason

Did you take the pot out to measure it?

Pics would help yes.

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http://pdfelectronics.com

Yup pix please! It's rare to have a pot short,usually they go open. better possibility is there is a problem with the associated wiring

At least disconnect it to measure.

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Stephen
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