The ground switch is easy available if you disable the power supply wires and death cap. If four digits are present, the first two digits refer to the year i. This is the phase inverter and vibrato tube. I suggested 15 amp contact ratings because the heavy duty switches are physically almost the same size as the 4 amp version, but the heavy contacts inside would not be affected as much by the initial power surge into the transformer, bridge rectifier and filter capacitor circuit and contact pitting might not be a problem with heavier rated switches. This tube should be of good quality.
Rectifier tube is 5U4.
This can be desirable for those who have a hard pick attack. The sticker is a Black and Silver label, which contains several lines for "sign-offs" at the completion of sound and electrical tests, where applicable. LumberghOct 1, Aftermost Fender tube amps switched to solid-state rectifiers, until recent Custom Shop models reintroduced tube rectifiers. This code is located on the "QA" Quality Assurance sticker, which may be found on the back of the amp chassis.