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I have read several threads about voltages being too low on 5E3 builds. But my voltages seem too high.
Sorry for the long post, just trying to include everything that might be pertinent.
I am using a NOS 5Y3. This is actually just a rebuild into a nicer chassis from a working 5E3 so unless something terrible happened, my OT, PT, and tubes are all OK. Something obviously changed, because all of my voltages are too high. Here are my measurements, all with tubes in and turned on but no guitar cable plugged in. On the previous build (with all the same components except for the chassis) the voltages at the filter caps were all ~30v lower.
420 vdc at 1st filter cap
386 vdc at 2nd filter cap
304 vdc at 3rd filter cap
225 vdc after PI (coming out of pin 6 of V2)
185 vdc after pin 1 of V2
27 vdc at 6V6 cathodes.
On the OT I am using a center tap (not an artificial one) and I am reading 3VAC between one pin of the pilot light and ground. That doesn't seem right either. The center tap is grounded.
Those seem a bit high based on what I have seen on schematics that contain voltages.
I did not measure them until I noticed that when playing through channel 1, everything sounded great until I turned the volume up to about 11. There i hear a slight click and after that the tone gets very raspy and buzzy (not the normal OD sound) and the volume dropped pretty significantly. Channel 2 works perfectly even when dimed. Also, the power tubes have a blue glow that shows up ONLY when the volume is turned past this point (yes, I read up on blue glow but including this info in the name of full disclosure, but I did read something about this occurring during crossover distortion). I get all the above symptoms regardless if I use a 12at7 or a 12ax7 in V1. The only mod to the build is that the cathode resistor is a 330 5W instead of the 270 5W. But this worked fine in the old build.
I wondered if the 1st vol pot had gone bad (because of the click and then the bad sound) or something until I measured the voltages. Something is not quite right here. I used a buss ground this time instead of a star ground, so I did put some heat on those pots to get the buss soldered to the back. But I don't see how a bad pot could cause high voltages. My suspicion is that the two problems are related.
The amp sounds fine (no hum, etc), it's just that when I turn up the volume as described I get a bad sound. Something is obviously wrong, and I am scared to run the amp at those voltages. I am just out of ideas. I'd appreciate any suggestions.
Sorry for the long post, just trying to include everything that might be pertinent.
I am using a NOS 5Y3. This is actually just a rebuild into a nicer chassis from a working 5E3 so unless something terrible happened, my OT, PT, and tubes are all OK. Something obviously changed, because all of my voltages are too high. Here are my measurements, all with tubes in and turned on but no guitar cable plugged in. On the previous build (with all the same components except for the chassis) the voltages at the filter caps were all ~30v lower.
420 vdc at 1st filter cap
386 vdc at 2nd filter cap
304 vdc at 3rd filter cap
225 vdc after PI (coming out of pin 6 of V2)
185 vdc after pin 1 of V2
27 vdc at 6V6 cathodes.
On the OT I am using a center tap (not an artificial one) and I am reading 3VAC between one pin of the pilot light and ground. That doesn't seem right either. The center tap is grounded.
Those seem a bit high based on what I have seen on schematics that contain voltages.
I did not measure them until I noticed that when playing through channel 1, everything sounded great until I turned the volume up to about 11. There i hear a slight click and after that the tone gets very raspy and buzzy (not the normal OD sound) and the volume dropped pretty significantly. Channel 2 works perfectly even when dimed. Also, the power tubes have a blue glow that shows up ONLY when the volume is turned past this point (yes, I read up on blue glow but including this info in the name of full disclosure, but I did read something about this occurring during crossover distortion). I get all the above symptoms regardless if I use a 12at7 or a 12ax7 in V1. The only mod to the build is that the cathode resistor is a 330 5W instead of the 270 5W. But this worked fine in the old build.
I wondered if the 1st vol pot had gone bad (because of the click and then the bad sound) or something until I measured the voltages. Something is not quite right here. I used a buss ground this time instead of a star ground, so I did put some heat on those pots to get the buss soldered to the back. But I don't see how a bad pot could cause high voltages. My suspicion is that the two problems are related.
The amp sounds fine (no hum, etc), it's just that when I turn up the volume as described I get a bad sound. Something is obviously wrong, and I am scared to run the amp at those voltages. I am just out of ideas. I'd appreciate any suggestions.
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