Yeah, it sounds like a cop-out, but I'm accustomed using a 'scope to follow the negative ALC voltage from the trimpot at R718 while modulating the radio at full mike gain in SSB transmit.
If you get the modulated negative DC in step with the mike audio, turning R719 will show an erratic change if the trimpot is bad or just dirty. This can cause the ALC to cut out. If you get nothing here, the list of suspects is pretty short. The diodes D702 and D703 don't fail very often, but if the radio is connected to an antenna during a storm, a big surge can still come down the coax if a nearby tree is struck. Any time those diode check bad, the disc capacitor C714 that feeds RF to them could also be bad.
If everything checks okay there, you should have the same negative voltage at the white/blue wire at terminal B43 on the audio board.
Never tried to learn how to do this with just a meter.
73