The PHILCO Phorum

What is the opinion of the multitudes about adding a mov on the line side of the radio. Given the modern power grids and there inherent power problems in the rural setting. Just a thought.

Just my opinion.
Tube electronics are not terribly vulnerable to the type of surges that an MOV is designed to squelch. Rarely could they get beyond a transformer and in the case of a transformerless set (domestic radio) there's not much to damage.

Hey Robert
I too would tend to agree with that. On the other hand, I live in Florida and we have a lot of lightning and switching transients on the line. Now a lightning strike in the right situation will damage/burn up/ hurt the feelings of your power tramsformer and take the MOV any way. I put one in mine anyway as a "hopeful help" in case of a surge event. I also put a thermistor in series with its AC mains. It provides a softer start at power on and also lowers the primary volts by 5-6 volts while operating and hasn't affected the performance.
By the way, MOV devices have a finite life span dependant on their exposure to surges. A 500 JJoule device will take, 1- 500 joule hit; 2- 250 joule hits; 100- 5 joule hits; (you get the idea)in its lifetime. There is not a practical way for the average person to test them and a bad one looks as good as a new one. Yup, all those power strips youve had all these years are likely in need of replacing too!

DCASAZZA, hi. Could you expand a little on that thermistor. Size ( Ohms, Watts etc.). I have 120VAC as most people do nowadays and was looking for a way, simpler the better, to knock it down a few volts to get closer to the 110 ACV the sets were designed for. PL

Many folks are using the CL-90 Surge limiter/"thermistor". Its specs are about right for normal radios like we usually work on. You can get a spec sheet at Mouser. They will knock you down a few volts in normal operation but they also add heat in doing so. They get quite hot. Slows down warm up time but not terribly.

I'm fond of the Dale/Xicon chassis mount resistors, mainly because I inherited a good stock of 18/22 ohm ones at a good price Other guys cob in a bucking filament transformer which is a no-heat solution and also works well but presents physical limitations.