Before I turned on my newly built amplifier for the first time, I wanted to be sure that I could do so safely without damaging the amp or injuring myself.  If there were a short somewhere in the amplifier, it could suddenly start drawing current from the wall AC outlet without any limit except for the 2 amp fuse built into the amplifier.  Of course, it could be too late by then, as components or transformers could be damaged by the sudden surge before the fuse could blow.  For this reason, I put together a series test lamp to act as a simple current limiter.  Here is a simple schematic from Tino Zottola’s Vacuum Tube Guitar & Bass Amplifier Servicing. Continue reading →