Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: pima1234 on May 13, 2011, 08:49:07 am
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Does anyone here know the resistance value of the pots used in the Maven Peal amps (specifically Ganesha and Tuskadaro)? Or, can you tell me how to test them to find out. The pots sold on hoffmanamps.com are the same as the ones used in my amps, but I don't whether they are 10k or 50k.
I tried testing the resistance with a good multimeter by touching the probes to the other end of a short 1/4" cable plugged into the 1/4" access jacks, with the meter set to 20komhs and then 200kohms but was getting a negative reading.
I'm not a tech, so I shouldn't open the chassis, you know. Or, maybe I need to finally start taking some electrical engineering classes!
Anyway, thanks!
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Do you have the owner's manuals for these amps? They should describe the bias setting procedure and the measurement values and units.
With the test jacks, you are not measuring the value of the bias pot itself, you are only measuring the effect of adjusting the bias pot. You'll have to open it up, or contact Mr. Zimmerman, to determine the value of the pots.
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Thank you. I was able to open the amp, and the pots I need are Piher Spain 20k 236M, which I can't find anywhere, even in the Mouser catalog. But, there has to be a suitable replacement available, I just want to make absolutely sure I get the right one. Dave's phone is not accepting calls right now, and he's not answering e-mails. He's been very helpful in the past, but I've expecting a shipment, which is supposed to include replacement bias pots, for some time. I understand what you said about measuring the effect that the adjustment has on the tubes, not the resistance of the pot itself. That makes sense. Thanks again for your reply.
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Any 25kL pot will do the job. No biggy.
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Excellent! Thank you.