The bias transistor blew on mine when the amp was only a few hours old.
I replaced it (not trivial), and never had another problem until a few
years later when a 3-500Z developed the dreaded cathode/grid short.
73, Duane
On Mon, 12 Dec 2005 20:28:17 -0700 "Henry Pfizenmayer"
<pfizenmayer@worldnet.att.net> writes:
> UPDATE : Yep another blwn bias transistor - second since about
> April.
>
> Also appears the HV is OK at about 3145 V no load as measured with
> an
> external Fluke DVM , so metering is messed up again.
>
> What I would like to know is what is others experience with bias
> transistor
> failures ? Bad 3-500 ???
>
> Hank K7HP
>
>
> Centurion readings after a POP
> >
> > Resting plate current at first division - about 70 ma.
> > Plate voltage only 2000 volts and transformer hum sounds like the
> supply
> > is loaded heavily but showing only the 70 ma on the plate meter.
> > No grid current
> > No fwd/reflected power
> > No difference in standby or operate
> > No difference QSK or PTT /VOX
> >
>
>
>
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>
--------------------------------------
Duane Calvin, AC5AA
Austin, Texas
http://home.austin.rr.com/ac5aa
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