If you are going to work on old/tube gear, you need a Variac. Back in the day, my hobby was refurbishing old tube gear. Mostly tube AM/shortwave radios, Transoceanic, etc. Letting the smoke out, is bad. Which can happen if you just plug them in and turn them on.
I built this Variac with a light bulb so if there is a short, you don't fry the circuit, the light just lights up. A 100 watt bulb is about one amp depending on voltage. If the light comes on, you know there is a short circuit. There are two outlets, one from the Variac thru the light, and one directly from the Variac. For the picture, I put my heat gun on for a load to show the light. If the light comes on, stop and start looking for the short. Usually it's in the power supply, transformer, or physical damage.
I learned from people wiser than me, when you get a new unknown piece of gear, or one that has not been on in years, it's a good idea to bring the voltage up slowly to give the electrolytic capacitors time to re-polarize so they don't blow up. This also gives the components time to dry out if there is moisture. My process is bring them up to 50 volts for 20 minutes if no light. then 70 volts for 20 minutes, then 90 volts, etc. By the time you get to 90~100 volts the radio/amp will usually start working.
I also do this with my amps, especially if they have not been on in years.
