Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Mike_J on February 03, 2021, 11:47:34 am
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The only thing I soldered onto the board for my 5f6a rebuild was the 50K trimmer pot. I am going to buy another one from Hoffman because I need more turrets and drill bits. Was wondering how much heat one of the trimmer pots could handle because originally I planned to remove it. Not that big of an issue because they aren't expensive and I need other things from Doug anyway.
Look what I found in storage. Either one of these things in conjunction with the center punch would have made a great board. Forgot I even had it. The bottom picture shows turret spacing that is 16" long. Must have gone to Office Max or somewhere to get this copied on 11" X 16" paper. That is what I am headed out to do after I order my parts. Having this all spaced out makes it much easier to do this well and I don't recall ever making a board over 16" long.. Wish I had remembered I had these tools. Would have saved a lot of work. Live and learn and forget and relearn and on and on.
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How much voltage can Doug's 10K Piher trimmer pots handle. Thinking about using a 10K to balance the PI resistors. Have used trimmers rated for 500VDC in the past for this purpose and might have one around here somewhere. If you use these in the bias circuit they don't need to handle the voltage I would need for the PI. Have a 10K Piher that looks like the picture on Doug's store site. Probably bought it from him some time ago.
Thanks
Mike
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How much heat at trim pot's legs could handle when unsoldered ?
How can I tel you ? Can you use a heat sink on each leg like a pliers if you are not sure ?
This one ?
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How much heat at trim pot's legs could handle when unsoldered ?
How can I tel you ? Can you use a heat sink on each leg like a pliers if you are not sure ?
This one ?
No you can't use a heat sink. No place to put it. I am buying a new pot. I am confident they can handle the heat when I install them as long as I am careful. Wondered if the heat of removing them once they were already installed would be too much for them. Best course of action is to just buy another trimmer pot. They are not that expensive. Thank you for responding.
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> balance the PI resistors.
Why? Even hi-fi amps don't do this much. The final stage tends to average-out errors. Pots go bad and this is a bad place to be bad. And guitar is NOT harmed by a little 2nd harmonic distortion.
How much voltage? About the same as the bird on the wire. 10,000V on both legs does no harm.
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> balance the PI resistors.
Why? Even hi-fi amps don't do this much. The final stage tends to average-out errors. Pots go bad and this is a bad place to be bad. And guitar is NOT harmed by a little 2nd harmonic distortion.
How much voltage? About the same as the bird on the wire. 10,000V on both legs does no harm.
Thank you for the advice. Not enough impact on tone to justify the risk you are suggesting. I will leave it out.