To expand on Andy’s comments a little: The light bulb current limiter is an important safety tool when powering up a new (or repaired) amp.
There are several web tutorials on how to build one, check out this link:
The switch in this example is nice but the circuit can be built without it (I did not include a switch in mine).
The idea behind putting a 100w light bulb in-line with amp circuit is that if there is a dead short in the circuit, the light bulb take the load and prevent the current from blowing the fuse (if you’re lucky) or frying some amp component (usually the power transformer).
When you use the current limiter, the light bulb will light up and then become dim as the circuit stabilizes. If the bulb lights up brightly and stays that way, there is a problem with the amp circuit.
The construction of the current limiter is very simple and inexpensive to assemble (maybe $2.00-3.00), I built mine from stuff already at hand in the garage.
Kendrick amps sells one too. The Kendrick current limiter page gives a good description of what the limiter can be used for. Here is the link: