No follow up as of yet, over 50% of parts ordered are on 2-4 week back order from Ameritron. Once the parts arrive and we have completed repairs I will post findings.
If the meter is half up it should be easy to trace. http://www.w8ji.com/al80b.htm
is a good current schematic and layout of the main PC board.
The meter board is in the AL80B manual. The front panel will drop, if you can figure it out, and allow you to test the broad without danger if you run the metering circuits off an external 12V supply. You do not need negative voltage, you do not need to plug the amp into the outlet.
Just apply 12V positive to the center pin of the rear panel 12V jack and it will activate all you need to test through the meter board.
As long as the meter is good and not stuck, my most likely guess would be a bad op-amp ( I think it is an LM324). A bad transistor would pin the meter. The 3904 for the forward is unlikely. If it shorts, the meter would pin. If it is open, the meter would be at zero. It very very rarely would be anything but shorted and pinning the meter. Op amps can be damaged easily, however, and can fail at about half voltage on the output. It could be something else, of course, but if it is a bad part is is most likely the op amp.