Following up on yesterday’s question, where an inSync reader asked for help tracking down a problem with his guitar amp. We suggested substituting a known-good preamp tube for each tube in the amp until the problem tube was found. In this case, this didn’t solve the problem, because two tubes had gone bad — apparently damaged during shipping or by dropping the amp. The problem was eventually solved by replacing all of the tubes in the amp, which ensured that there were no problem or weakened tubes left.
There are two things we can take away from this:
1. Having just one known-good replacement tube on hand may not be enough — keep a selection of spare tubes handy.
2. Vacuum tubes are fragile glass bottles that can be easily damaged by mishaps. Treat your tube devices wth care!