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Hey yinz'all, I've got a late 60's Ampeg G-12 on the fritz. Over the years I've gotten to know it pretty well, replaced the big multi-cap, all the electrolytic caps, the higher value resistors, a blown output transformer and a tube or two. But I'm a total hack. The other day I powered it up to dead silence; only the power tube in V1 position would light up.
A while back I rewired the tube heater circuit with a twisted pair off the board which reduced hum dramatically. The amp's worked flawlessly since, but I tend to assume my work is the most likely source of a problem, so I figured I'd check that first. However, after getting the chassis out of the cabinet and reconnecting everything, with the amp plugged in but before powering it on I happened to touch the center of the power transformer. I got a mild zap. So I'm a little suspicious that maybe the PT is fried. Powered on, I went to check the heater voltage: I read 3.2V at each each connection except V1, where pin 2 reads 2.8V. They're supposed to be 6.3V on the schematic.
Pin 2 on V1's solder looks oxidized, so I'm planning on cleaning and re-doing it... but would one poor connection cause the entire circuit to drop voltage, rather than just short? Am I right to suspect the PT? Any other likely suspects or tests I can run to be sure? I'd hate to go through the trouble & cost of replacing the power transformer to find out something else was the issue.
Thanks in advance!
A while back I rewired the tube heater circuit with a twisted pair off the board which reduced hum dramatically. The amp's worked flawlessly since, but I tend to assume my work is the most likely source of a problem, so I figured I'd check that first. However, after getting the chassis out of the cabinet and reconnecting everything, with the amp plugged in but before powering it on I happened to touch the center of the power transformer. I got a mild zap. So I'm a little suspicious that maybe the PT is fried. Powered on, I went to check the heater voltage: I read 3.2V at each each connection except V1, where pin 2 reads 2.8V. They're supposed to be 6.3V on the schematic.
Pin 2 on V1's solder looks oxidized, so I'm planning on cleaning and re-doing it... but would one poor connection cause the entire circuit to drop voltage, rather than just short? Am I right to suspect the PT? Any other likely suspects or tests I can run to be sure? I'd hate to go through the trouble & cost of replacing the power transformer to find out something else was the issue.
Thanks in advance!
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