I've got a couple:

1.Get a schematic and replace the components in bias circuit(s) of the
PA.
then
2. Get a service manual and retune the PA setting bias as indicated.

3. (you might get away with just 2.)

4. Then again it could be the ALC ;-)

(....5. or the drivers)

Aternatively send it off to Castle Electronics as they seem to know
what they are doing - they rarely quote input power in terms of Volts
DC for example.