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Bigtime Lost output and crazy high voltage readings (540 volts AC) on rectifier tube heater. (Excessively High DC voltage (12 to 17 volts) readings on tube heaters also).
I was screwing around - testing old junk tubes on my previously well functioning Magnavox (2-6v6, one 5y3 and with mini preamp tube I forgot the number).
At one point, my volume and tone controls had beccome half disconnected - via the RCA jack on the chassis. This caused much hum and squealing. Unplugged unit ASAP.
After finding that problem, I began testing some old 6v6 tubes (ebay) with my guitar connected. I replaced the Magnavox 6v6 tubes with a pair of GE or something. At first, they sounded good. Then sound began cutting out and in. Out and in. Shut off amp.
Then I tries some Sylvania 6v6's. No sound except some hum.
When I replaced my original Magnavox tubes, half my output or more had gone away.
I noticed red hot areas on top of the 5y3 that I thought I hadn't noticed before.
I checked with my cheap Chinese Digital mutimeter and found voltage readings that are way out of the norm.
540 volts AC on the yellow leads from the power trans to the 5Y3 rectifier tube. Yikes! Isn't that supposed to around 15 volts DC? The red striped leads on the bottom read 249 volts AC.
540 volts were found on the pins of the output tubes. 405 volts at the cap can. Green heater wires for the preamp and output tubes read 12.5 DC volts intially. After a few minutes, the voltage climbed to 17 volts DC. The bulb never blew out.
My thinking is that my PT got fried.
Please advise.
Forgot to add that smoke came from somewhere at some point when testing the bad tubes. I could not detect from where the smoke had come. When I unplugged the amp and turned it over, I could not trace it. The amp still operates, but at less than half the output it had prior to my screwing around tube testing. And those readings seem scary.
I was screwing around - testing old junk tubes on my previously well functioning Magnavox (2-6v6, one 5y3 and with mini preamp tube I forgot the number).
At one point, my volume and tone controls had beccome half disconnected - via the RCA jack on the chassis. This caused much hum and squealing. Unplugged unit ASAP.
After finding that problem, I began testing some old 6v6 tubes (ebay) with my guitar connected. I replaced the Magnavox 6v6 tubes with a pair of GE or something. At first, they sounded good. Then sound began cutting out and in. Out and in. Shut off amp.
Then I tries some Sylvania 6v6's. No sound except some hum.
When I replaced my original Magnavox tubes, half my output or more had gone away.
I noticed red hot areas on top of the 5y3 that I thought I hadn't noticed before.
I checked with my cheap Chinese Digital mutimeter and found voltage readings that are way out of the norm.
540 volts AC on the yellow leads from the power trans to the 5Y3 rectifier tube. Yikes! Isn't that supposed to around 15 volts DC? The red striped leads on the bottom read 249 volts AC.
540 volts were found on the pins of the output tubes. 405 volts at the cap can. Green heater wires for the preamp and output tubes read 12.5 DC volts intially. After a few minutes, the voltage climbed to 17 volts DC. The bulb never blew out.
My thinking is that my PT got fried.
Please advise.
Forgot to add that smoke came from somewhere at some point when testing the bad tubes. I could not detect from where the smoke had come. When I unplugged the amp and turned it over, I could not trace it. The amp still operates, but at less than half the output it had prior to my screwing around tube testing. And those readings seem scary.
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