so ive been chasing this one for a couple weeks now and im starting to think its a PA board issue but wanted to see if anyone here has seen this before. basically my 7300 is putting out maybe 30-35 watts max on 40m regardless of what i set the power to, every other band is fine, hitting full 100w no problem. ALC looks normal, SWR is fine, antenna hasnt changed. tried two different antennas just to rule that out.

i did the usual stuff, checked the driver output, reseated the connectors on the PA board. nothing obviously burnt or shorted when i look at it. the radio doesnt throw any error codes which is annoying because at least that would give me something to go on. was wondering if anyone has had similar and whether its usually the band-specific filter section or something on the PA itself that goes like this. i have a service manual but the fault isolation tree in there is pretty vague honestly.

radio is a few years old, bought used, so no warranty to worry about. not afraid to get in there and poke around but want to make sure im not chasing the wrong thing first.

had something almost identical on a friends 7300 last year. turned out to be one of the LPF relay contacts on the 40m filter had corroded enough to add resistance and drop the output. you can actually check this without too much digging if you have a way to scope the signal before and after the filter section. the symptom was almost exactly what you're describing, fine everywhere else, just 40 crapped out. icom used some relays in that era that dont love humidity apparently.

before you go too deep into the PA board id definitely check those relay contacts first, its a much easier fix and cheaper too. deoxIT and careful burnishing got the one we fixed back to full output. been running fine since as far as i know.

might be worth checking the bias on the finals too while youre in there, sometimes they drift and it shows up on certain bands more than others depending on how the drive is distributed. not saying thats definitely it but if youre already in there with a meter you might as well look. what firmware version is it on? i vaguely remember something about a power calibration issue on older firmware but im not sure if that was 40m specific or not, could be totally unrelated.