Quote:
Originally Posted by miniman82
True, but if you know the museum like I do having that many vintage sets running at the same time has about the same effect on the line as a variac does...
I can tell you that some sets do not like high line voltages, some don't care. I had a portacolor and you could run it normally no matter what the line voltage was, because of the type of HV section it had. Early RCA sets don't like high input voltages, because they can and often will cause the flyback to run hot. You can verify by monitoring horizontal output tube cathode current at various line voltages, the worst offenders are sets with silicon B+ rectifiers because they are more efficient than a vacuum tube. It's not hard to go out of spec on horizontal output current, and when you do it's not hard to burn out irreplaceable parts. I'm anal and don't like looking for unobtanioum flybacks, so I never run a set for extended periods without a variac.
Zenith sets tended to be more robust than RCA, so I personally wouldn't worry till line drifts past 120. But again, only way to know if you're in the 'flyback melting danger zone' is to read horizontal output cathode current, and if it's higher than called out in the schematic don't be surprised if things get too hot.
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+1 to the above. My dad (a TV tech for ~50 years) used to say the worst you could do to a TV was to turn it off - they want to be on....
I've got high line voltage (127V most days), but never run a variac - I have a Sola power line conditioner (thank you DoD surplus!) that I use. My entire bench is wired through it now, and no matter the input line voltage, the output is 118V, and it also smooths it, running the juice through an EMI filter. Heavy, yes, but no having to set a variac. I have a smaller (still heavy!) one here in the house that I use for my sets.
One additional benefit - my bench lamp bulbs last a long time and my bench DMM (an old 70's Racal Dana) doesn't "hunt" with no input.