OK, we all know that in an AA5 radio, that having an open filament in the pilot light can cause the rectifier to fail. (Don't we?).
So testing pilot lites can be done a couple of different ways. A multimeter- just tells you that the fil. is good.
A better test is to put the correct voltage on it and see how bright it is. Some glass can become dark from emitted filament material, and a multimeter test won't show how bright the bulb is.
Some models of tube testers have a socket for testing pilot lights. Kinda handy at times.
Did you know that pilot lights can short? Well, they can, and it can lead you a merry chase as to why the fuse keeps blowing.
Be sure to check the wires at the BOTTOM of your pilot light socket. At this point in time, the insulation can fall off the wires, and that can cause a short- or worse, a fire.
Note: Some pilot light sockets are really easy to re-lead. Some are not.
If you are using a transformer fed radio, why not replace the 6V pilot lights with the 6-8 volt types, as they last a lot longer because they are designed for higher voltage. I have seen minimal brightness difference. (Remember- line voltage is now 120-125V+ these days, and the transformers can put out a higher voltages than originally designed for.
It's also a good idea to run the sets with an isolation transformer that has adjustable output taps to reduce input voltage to 110V.
Hint: Replace your [You must be registered and logged in to see this link.]
pilot lamps with [You must be registered and logged in to see this link.]
's. They draw less current, and the transformer can run cooler.
Use # 47's in the AC/DC sets, as the 35W4's filament is tapped and it needs a balanced current through it, as the pilot light becomes part of a parallel resistor with the filament of the rectifier.
Finally, if you don't want to have to tear the set back apart to replace pilot lights that fail just after repairing them I present this tip:
Hold the pilot light by the base and "thwack" it with your other hand, like you are flicking a bug off of your nose. About as hard a hit as you want someone to thwack your nose.
If the filament is mechanically weak, or on it's last life, the filament in it will break/ open, and you can replace it while you have the set apart. Sounds weird, but it really works effectively.