Brian,
The real mystery is that this initially occurred when you removed the
KPA100 to tighten the PA transistor screws. I really would not think
that would trigger a component failure, so I encourage you strongly to
look for a bad solder connection.
Be certain the wire from the center of the SO239 to hole 6 of the T4
connections is in place and well soldered - that one is easily
overlooked. Do the rest of the T4 connections look 'like mountains, but
not volcanoes'? Re-strip if they have that volcano appearance.
You might also check R28 and R29 too. A bad capacitor is a difficult
thing to find - fortunately they are not encountered often, but check
anyway.
Measure the resistance from the wiper of R26 to ground - it should be
close to 43k.
A possibility is that R26 itself was ready to fail - it perhaps worked
until it was touched.
You could possibly use some other diode at D16 and D17, but I don't know
the response characteristics vs. frequency. The 1N4148s will work fine
down to about the 2 watt level, I don't know how low you wish to have
accurate power control and indication. Elecraft will likely send you
1N5711s if you can't find them locally.
73,
Don W3FPR
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