• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Clean your tube sockets!

I recently had egg frying noises and popping in a vintage EICO integrated amp. Got rid of it by cleaning both the tube pins and the sockets first with the Deoxit D-series contact cleaner and then applying deoxit Gold. For the tube pins, I used a Q-tip. For the sockets, I used interdental brushes. Frying noises went away and the popping is now infrequent. Might need a second treatment. Deoxit makes a kit specifically for tube gear but I haven't used it.