If you connect an NE-2 neon bulb from the emitter to collector of the
cathode switching transistor, it will keep spikes from puncturing the
transistor.
73
Phil
VFO Stabilizers and PEP adapters for wattmeters...Check out
http://home.comcast.net/~k4dpk
----- Original Message -----
From: "Duane A Calvin" <ac5aa@juno.com>
To: <tentec@contesting.com>
Cc: <tentec@contesting.com>
Sent: Monday, December 12, 2005 11:22 PM
Subject: Re: [TenTec] Centurion- bias transistor
> 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
> > >
> >
> >
> >
> > _______________________________________________
> > TenTec mailing list
> > TenTec@contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
> >
> >
>
>
> --------------------------------------
> Duane Calvin, AC5AA
> Austin, Texas
>
> http://home.austin.rr.com/ac5aa
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
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