so this has been driving me nuts for about two weeks now. my 7300 is behaving totally normally on every band except 40m where im only getting maybe 30-35 watts out at full drive when i should be seeing closer to 100. the ALC looks a little weird too, kind of jumpy when it wouldnt normally be doing that. i swapped coax and tried a dummy load so its definitely not the antenna system. SWR is flat on the dummy. the rig reads its own output power the same way my external meter does so at least the metering isnt lying to me.

ive had it about 3 years, doesnt get run super hard, mostly digital modes at 50% power. nothing got wet, no lightning nearby that i know of. just woke up one morning and 40m was soft. havent opened it up yet because i kind of wanted to see if anyone had seen this before before i started poking around. anyone dealt with something similar on one of these?

yeah the 7300 has a known thing where the finals can start going soft on individual bands, usually shows up on the lower HF bands first. the PA board has per-band switching and sometimes one of the switching transistors gets flaky before the actual finals fail completely. before you pull the board i'd check if there's any corrosion around the band switch area on the PA, ive seen a few of these where moisture got in through the back panel and did some quiet damage. also worth checking the RF output on the test points while you drive it to see if the drive signal to the final stage looks right on 40 versus a working band. if drive looks good and output is still low youre probably looking at one of the finals starting to degrade.

Icom service manuals are actually pretty decent and freely available, worth downloading the full thing before you start. the PA board isnt the worst thing to get to but its not exactly simple either.

did you check the LPF board? the 7300 has individual low pass filter relays per band and the 40m relay contacts can get worn or oxidized. i had an older icom years back that did something similar and it turned out the relay wasnt making solid contact so you'd get partial signal loss rather than a complete failure. a relay on its way out can do weird stuff to ALC too because the reflected/forward sensing isnt seeing a clean path. might be a cheaper fix than dealing with the PA if that turns out to be it.