Uploaded October 2021 | Updated September 2026, 2 days ago
Back to troubleshooting this guitar amp. I've had this old tube amp for years, and it always had a problem. It worked fine at low volume, but I couldn't turn it up very far on either channel, before it got to the point where it would break up uncontrollably on louder notes. I've pretty much rewired the whole amp. Partly to make room to take measurements, and partly to work through the schematic, checking that it was all correctly wired. Also, the lead dress was appalling, and may even be the cause of the problem. I also replaced the filter capacitors, since they were 20 years old, plus however long they sat on the shelf. In this video, I fix some errors in the ground scheme. While I had the amp open, I also cleaned the gunk off the circuit board, and cleaned the contacts in the tube sockets and potentiometers.
I also found that the mains transformer wasn't securely bolted down. Hopefully, fixing that will reduce the hum.
Back to troubleshooting this guitar amp. I've had this old tube amp for years, and it always had a problem. It worked fine at low volume, but I couldn't turn it up very far on either channel, before it got to the point where it would break up uncontrollably on louder notes. I've pretty much rewired the whole amp. Partly to make room to take measurements, and partly to work through the schematic, checking that it was all correctly wired. Also, the lead dress was appalling, and may even be the cause of the problem. I also replaced the filter capacitors, since they were 20 years old, plus however long they sat on the shelf. In this video, I fix some errors in the ground scheme. While I had the amp open, I also cleaned the gunk off the circuit board, and cleaned the contacts in the tube sockets and potentiometers.
I also found that the mains transformer wasn't securely bolted down. Hopefully, fixing that will reduce the hum.
