[Amps] 8877 hipot

Tom W8JI w8ji at w8ji.com
Wed Oct 11 12:21:40 EDT 2006


>I just bought a 8877 on Ebay advertised as new...I just 
>tested it on my
> hipot and found it draws 40 microamps(Cold) at 
> 4000vdc...Comments from amps
> guys? Guy says to return and he`ll refund my money if it`s 
> not DOA!
> Wow,screwed Huh? Jim K7RDX..

Jim,

I assume you have a dc highpot.

Why don't you run the filament (with airflow) for a few 
hours and see how the tube tests?

The good 8877's I test hold off about 12-15kV from anode to 
grid before breaking down, and they flash on the outside of 
the tube normally. Normal peak operating dc in an amplifier 
is almost twice the dc anode voltage when operated normally, 
and can easily be several times that voltage when mistuned.

It does sound like you have a bad tube.

73 Tom 




More information about the Amps mailing list