[Elecraft] Help - XV432 output pwr drops

[Colin VE3MSC]

HNY 2011. Just built an XV432 transverter and am a bit stumped - 
Alignment was tricky as the output power keeps dropping as it heats 
up. Something's not right, looking for suggestions.
I get about 13-15W out and it drops to about 9W after 1min, down to 
6W in 5mins.  Using signal generator.  If I crank the drive up, I 
will get more out, but see the overdrive leds start to come on.
I've checked all test points and voltages, and only ones atypical are:

U7 (RF module) Pin 3 is 2.25V instead of 3.5-4.5 per manual.
TP5 8.0V and drops as things heat up.
TP6 is 1.9V @13-15W

Also, TP1 4.95V instead of 2.2 nom (I'm not worried about this - its LOsc).

Any ideas?
73 VE3MSC
Colin