Sounds like a grid-filament short. It's common with 3-500Z's.
On 4/8/2011 9:12 AM, Shane Youhouse wrote:
> Tuned up the SB220 last night (Hasn't been inline for a week or so).
> Everything as normal.
>
> Flip grid current meter to grid, key the exciter, PINNED (Guess I'm doing
> back to back diodes today :) ) Unkey, it lightly pins reverse... Almost
> didn't notice it.
>
> Look inside, nothing "glowing", everything looks normal.
>
> Turn it back on, try it one more time, same thing..... I tried SSB, and
> keydown, no drive I had a third to half scale positive grid I.... ANY
> amount of drive will cause it to pin, HARD.
>
> The zener has been replaced with a string of 5408s and a largish cap about
> 10 years ago. I have had a spat of bad caps in this amp.
>
> Haven't ripped into it, just shut it off last night and went to bed..
> Bummer, 80 was open across the US.
>
>
> Thanks, in advance.
>
> --Shane
> KD6VXI
>
--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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