I guess I spoke too soon or its just the luck of the Irish. I was sitting in
the shack with the SB-220 turned on but in standby when all of a sudden a
very loud snap. No crackle, no pop, just one hell of a loud snap.
Here's the setup; the amp was on in standby on 10m, multi-meter in the
Relative Power setting and in SSB mode. Immediately after the loud snap I
did some very quick checks. Plate voltage was OK but the Grid meter was
pegged FSD. Immediately shut the amp off and went for a Guinness Stout. With
the blood pressure still high, left ear ringing, and not in the best of
moods, I decided to leave further investigation until tomorrow. I suspect
the .82 ohm resistor and the glitch diodes across the plate meter blew.
Confirmation of this will have to wait until frustration level subsides.
So here we go again. Do I chuck Harbach's grid parasitic suppression and
return to Heath original, ground the grids directly or apply someone else's
grid parasitic suppression kit?? or.......nah, that would be to easy.
At least this time it didn't appear to blow the hell out the amp so some of
the mods have done their job. But, the cure must be found as I'm getting
tired of replacing that same .82 ohm resistor.
I notice that Harbach has redesigned his rectifier/metering board,
apparently adding heavier duty meter protection diodes, however, I don't
think they have anything to do with the .82 ohm resistor popping.
Where do I go from here? Rather frustrating when the darn thing worked so
well for about 2 weeks. I'll open her up tomorrow and report if I find
anything blown other than what I already mentioned as to what I believe has
popped.
Still open for suggestions (constructive of course).
Happy Saint Pat's Day!
Walter - VE3EN
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