In article ,
-ex- wrote:

Jim Flanagan wrote:

Hi...
I have very little experience with vacuum tubes and would like to
know what is an acceptable tolerance on the filament voltage. I am
planning on using some 6U8A tubes in a homebrew receiver. The data
sheet that I saw mentions no tolerance on th 6.2V filament. Would +/- 1V
be OK? Any help would be appreciated....

Thanks..
Jim
WB5KYE

Thats a bit too much...but not catastrophic either. Figure on about +/-
10% max with a fresh tube. An older wornout tube might not like even
that much reduction.

Agreed: the filament is just like a lightbulb, and increasing the supply
voltage will *drastically* shorten the life. (Reducing the voltage will
extend the life, similarly, at the expense of reduced output. I think
it's something like 12% overvoltage will cut the working life by 50%,
but I may be mistaken on that.

Chris.

--
Service with a capital "Bugger Off".