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
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