Thanks Tim. Mine just says Biasing diode, 10VDC 1.2 amps Semtech SA-5534.
Seems there a several revisions out there to the manual on this amp.
On 11/1/06, tim jenkins <jenkins@bellsouth.net> wrote:
> 10v zenor is what mine showes for d1, tim kv4bk
> >
> > From: "A.R.S. - W5AMI" <ars.w5ami@gmail.com>
> > Date: 2006/11/01 Wed AM 06:51:21 EST
> > To: amps@contesting.com
> > Subject: [Amps] Henry 3K trouble
> >
> > Hello,
> >
> > I have a Henry 3K Classic (8877) which developed a problem a couple days
> ago.
> >
> > I'm hoping some long time Henry types (or anyone else) might steer me
> > in the right direction.
> >
> > First, there was an arc over between the chassis and the bottom of the
> > plate choke where the HV connects. This caused R106 in the HV supply
> > to blow. I had spare 25 ohm 25 watt wire wounds and replaced R106.
> >
> > The HV came back after replacing the resistor, however now my grid
> > current goes way high. Even keying the amp with no audio on SSB shows
> > about 15 to 20 mils of grid current.
> >
> > When I applied some excitation (maybe 5-10 watts), it did indicate
> > output and plate current, however not knowing if the meter was reading
> > correct or not, I did not take much time to measure actual output for
> > fear of losing the grid. With 20 to 40 watts of drive, the grid
> > reading nearly goes off scale with no effect turning the load cap.
> > SWR is 1:1, so no problem there.
> >
> > I swapped the tube with a spare known to be good and the results were the
> same.
> >
> > At this point, my ideas on the problem are guesswork. I suspect the
> > bias diode for the cathode, or the metering circuit for the grid
> > meter. Oddly, the schematic shows only one diode D1 for the bias,
> > however in my amp, there are clearly two in series that appear to be
> > OEM, so that in itself throws me off. I plan to take the diodes out
> > of circuit today and check them for lack of any other ideas. BTW, are
> > these Zeners? The manual just calls it "bias diode".
> >
> > Also, can anyone tell me what D105 is for? This is a small metal can
> > diode hooked directly to R106 on the HV- lead. When I replaced R106,
> > I failed to check this diode, and since it is physically attached to
> > R106 parallel to ground, I suspect it could have been damaged when
> > R106 blew up.
> >
> > As you can probably tell, I'm sort of pulling at straws right now, so
> > forgive the ramblings.
> >
> > I would really appreciate hearing from any experienced 3K folks that
> > may shed some light on what I need to be looking at. In the meantime,
> > I'm going to find some corona dope and patch up the point of arcing so
> > that doesn't happen again.
> >
> > Thanks,
> > Brian / w5ami
> >
> >
> >
> >
> > --
> > "There is nothing more uncommon than common sense." -- Frank Lloyd Wright
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
>
>
--
"There is nothing more uncommon than common sense." -- Frank Lloyd Wright
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