I'd be most concerned with the filament voltages. I normally see 730V on the HV here, which is just over 700V under idle conditions.
I don't seem to have a problem with cathode emission issues with any of my equipment that runs on 125VAC. My station's tube gear is fed through a 10A Variac set to 115VAC output. This doesn't include my 13.8 supply that runs All Things '12V'", which has lasted me 30 years.
I do believe that some folks worry too much because most "110V" equipment really was designed for 120VAC. Exceptions can be made for pre-1960's equipment. The Collins lads are particularly obsessed with it -- and they KNOW that their gear was designed for military use -- where stuff is running on generators and whatnot...
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
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On Thursday, April 24th, 2025 at 11:34 AM, n4buq <n4buq@...> wrote:
I'm noticing that the HV from my rebuilt AC-4 is running quite high - on the order of 730VDC. I know that my line voltage is around 126VAC and if I run the AC-4 from an autotransformer, I have to dial that back to approximately 110VAC to see 650VDC output. I find that just a bit odd since the input voltage on the schematic shows 120VAC.
I can reduce that input voltage with either a bucking transformer or I also have a rather heavy-duty transformer with multiple input taps where I can feed my line voltage across the 132VAC connection points and have 110VAC at the 115VAC tap.
I'm just wondering why an increase of 6VAC from the original spec has the output voltage so high and whether that increase is detrimental. I realize the filament voltages are probably on the high side as well (I haven't checked those) but that may be harder on the tubes than the HV increase but I don't know that for sure.
Any thoughts?
Thanks,
Barry - N4BUQ
