What causes excessive power tube cathode voltage?

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Re: What causes excessive power tube cathode voltage?

Post by yello »

JMPGuitars wrote:
Mon 03/06/23 9:51 am
yello wrote:
Sun 03/05/23 1:42 pm
Thats part of the problem, I'm not sure what the voltage is supposed to be before the rectifier. Schematic only lists voltage after the rectifier and after the first power dropping resistor.

I tried a different 5y3 and got the exact same voltages so thinking the tube itself isn't the problem.

What is a reasonable plate voltage for 6V6's?
Get the voltages anyway. Don't you have more than 1 of these amps? You seem to have 30 of everything. 😉
I did measure the voltages in the amp, with different rectifiers, and with different setting on R40 the variable 500r resistor, that is what I am exploring currently.

While my other similar amps aren't exact in the circuit, a few have the same PT and B+ scheme. I measured 3 of them yesterday, and came up with a range of voltages, and also reached out to a friend who measured his same amp and I got those voltages.

This amp in question does seem to have about 15-20 volts higher coming from the same type of PT as the other amps measured above. That said, tube dissipation is fine at about 90%, and the plate voltage on the RCA 6V6GT tubes is around 370. Amp seems to be happy and sounds good.
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