Yaesu FT-902DM ALC problem

[mw0uzo]

In the middle of a faultfinding session and thought I'd share my problem with the fine minds out there. Got an FT-902DM on my bench. Problem is low power output on SSB of approx 50W. CW mode is fine at 100W+. The ALC kicks in way to early on USB or LSB, restricting the power. No ALC indication in CW mode - normal?

Thoughts:
1) In USB or LSB the SG supply voltage might be low indicating a supply voltage switching problem between SSB, CW and FM, AM modes. Will test this tomorrow.

2) I can't find the ALC adjustment. Spent ages looking for it, maybe there isn't one and power is regulated by (1). Could the ALC voltage be too much due to a resistor going high in the final?

3) Mode switch appears to have taken a knock. Perhaps a switch on it has been damaged, resulting in incorrect SG supply voltage selection?

[mw0uzo]

Its not (1) or (3). SG is ~215V on CW, LSB, USB and 165V on FM,AM,FSK.

[mw0uzo]

Fault has cleared itself after partially removing and checking mode switch. (Measured SG AFTER doing so.) Cleaned and pushed all the contacts down a bit so they had a better contact. Perhaps impact to mode switch displaced a contact slightly. Fault did not seem to be intermittent when mode switch was waggled though... hmmmm. Got a feeling I haven't seen the last of the problem.

[N8YX]

I have the service manual for the 90x series. Let me poke around a bit and see what I can deduce.

(Also have two FT-901DMs at the moment so I could check condx as required.)

[mw0uzo]

Problem has not returned :)
Been through the diagrams and can't confirm the exact failure mode. A bad contact for SG would have dissipated a fair amount of heat in the switch for what I was seeing plus it would have been mechanically sensitive. Hopefully it won't return..
Thanks for the offer of help.