Most of us have old tube testers that we use at times.
Some folks have wondered: "What's that funny sort of socket in the middle of some Septal (7 pin large base) or octal sockets?
Well, it's for testing bayonet or screw in type pilot lights.
Just set the filament selector for the correct voltage and touch the pilot light to the center terminal and sidewall of the "socket" within a socket. If it lights up, the bulb is good.
But "Wait" you say. "I can test that bulb with my multimeter". Yes, you can, but it does not tell you how bright the bulb is. Nor will a meter tell you if the filament opens under load, (or is shorted) just that cold it has continuity.
I have seen some with totally dark glass and no light from the bulb, but they test good on a meter. This alleviates that problem.
Hint: When testing pilot lights in a radio or TV set, flick the bulb glass with your finger, about as hard as you want someone to flick your nose.
If the bulb still produces light, great, use it. If it goes out, it means the life span of the bulb was at an end.
I learned this trick years back and sure saved me from having to remove a lot of chassis again to replace a bulb that failed in a month or so. Some pilot lights can be a nightmare to replace in the recesses of some of the early TV's and Radios.
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