[Elecraft] [KX1] Power drops after a few minutes of CW xmitting

[Chip Stratton]

My KX1 was behaving normally (as far as I could tell) before installing the
ATU, 30/80, and Power mod kits, though power output was a bit low on 40 and
20 (1.5 to 2 watts at 13.5 volts).

After installing all the extras above, the KX1 will seem to operate normally
for 5 to 10 minutes, but then power output will suddenly drop from about 3
watts to about 1.5 watts, receive signal strength will simultaneously drop,
and if I ask the ATU for a tune, the relays will clatter and it will seem to
come up with a new LC combo. This is with 13.5 volts input. Battery voltage
does not show a larger drop while transmitting (about .2 to .3 volts), but
the current draw does decrease with the drop in output power. This behavior
occurs on all 4 bands.

I've gone over the boards pretty carfully, but haven't been able to identify
any shorts/bad joints/etc. but of course that doesn't mean they may not be
there.

Any ideas on where to narrow my search for the problem?

Thanks,
Chip
AE5KA