so this has been bugging me for a couple weeks now. my 7300 is running maybe 30-35w max on 40m when i tell it to do 100w. every other band is totally fine, checked 80, 20, 15, 10 and they all hit 100w no problem. ALC looks normal, the SWR is flat into a dummy load so its not an antenna thing, and the display doesnt show any faults or warnings.

i did the fan mod on it last year and nothing else has been touched internally. power supply is a good astron 35A and the voltage is solid at 13.8. i tried a full reset on the radio too and no change.

anyone seen this before? im wondering if its a PA transistor issue specific to that band or maybe something in the LPF switching. i dont have a scope at the moment which makes this harder to diagnose obviously. been running it as-is on other bands but id like to get this sorted before winter contest season.

yeah that pattern — one band low, everything else fine — almost always points to the LPF relay or the relay driver for that band segment. the 7300 has a relay board that switches the low pass filters and those relays can get flaky, especially if the radio has seen a lot of use. worth pulling the covers and looking at the relay board, sometimes you can see a burnt or corroded contact if you look carefully.

the other thing i'd check is the LPF coils themselves for that band but honestly the relay is the more common failure point. icom service manual has the relay designations labeled pretty clearly. if you have a DMM you can at least check coil resistance on the suspect relay and compare it to the others. replacement relays are like a few bucks each if you can identify the right part number.

had almost the exact same thing on my 746 pro years ago, different radio i know but similar architecture. turned out to be a cold solder joint on the driver stage for that particular band. wasnt visible without a magnifier and a good light. resoldering that area fixed it completely. not saying thats definitely your problem but worth looking at the board under magnification if you go in there anyway.