Rob French (KC4UPR)
One more update. Hopefully this will help narrow things down.
This occurs about 10% of the time, where when I go key down, I get ~300 mW output power.
An additional thing I noticed...
When I measure (using the built-in RF power meter) the level at the drains of the final amp transistors, I always get a solid "5.2" on the display. However, when I measure it at the output BNC center pin, it varies between 3.8-4.5... or else 0.32 or so. So even when I am getting "good" output power, it's still not the same as what I'm seeing at the output of the finals. More to the point, when I measure it at the transistors, the reading is very steady... constant 5.2. When I measure it at the LPF output, it wanders a little.
So I suspect this all indicates more and more that it's a problem in the continuity of the LPF, although I'm still surprised that I never see it change while key down (except for the slight wandering during the high power out). What is the chance that this could be a problem with the LPF capacitors, and/or the coupling capacitor (C29 I think)? Should I just go replace these all as a matter of course?
Also, for the coils, should I just remove, rewind, and reinstall, possibly with manually removing the enamel? I attempted to use the "burn of the enamel" technique... maybe that just didn't work for me.