Hi Peter;
It definitely had one bad FET on the LPA when it was here, I do not see
in the report that it was intermittent, so I may not have looked closely
for those types of failures.
If you are sure it makes MW power when it is in the failure state, then
it is highly likely the LPA.
Inspect D1 closely, I have seen one side have poor solder, or it can
heat and the solder crystallize. Re-flow solder.
Pull the KPA3 but leave the KPAIO3 riser board and you can run it with
just the LPA.
Disregard errors about KPA3 or set it to "not inst" while you are
working on it.
Then set for several watts (not 5 exactly) and long press XMIT to go
into TUNE, IE transmit a carrier. (TUN PWR must be at "nor").
Then take a stick and tap around on the LPA. Around D1. Also the
green/red enamel on T1 & 2 can fail and the windings can short.
Tap the three bias pots, sometimes they fail internally, or their solder
points.
Look at all parts for solder problems.
You can put it in the fridge and chill it down to encourage failure, or
leave it on for an hour with a blanket over it to heat it up.
Keith WE6R
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