so this has been bugging me for about three weeks now. picked up a used 7300 from a guy at the club swap, seemed fine at first, put it on the bench and noticed it was only doing around 28-32 watts max no matter what band or mode i put it in. ALC looks normal on the display, power output slider is all the way up, and i already reflashed the firmware thinking maybe something got corrupted at some point. no change.

i pulled the lid and dont see anything obviously cooked, no burnt smell, all the finals look intact visually. i havent probed anything yet because im waiting on a few components before i tear into it further. the SWR is fine, dummy load shows flat, so its not a matching issue. the guy swore it was working perfect but honestly who knows.

has anyone seen this specific behavior on a 7300 before where it just kind of... plateaus at low power and doesnt throw any fault codes or anything? wondering if its a bias issue on the PA or maybe something upstream in the drive chain before the finals even see signal. would love to hear if somone has been down this road before digging into it myself.

yeah i had almost exactly this on a 7300 about a year ago, different story behind it but same symptom. turned out one of the PA transistors was partially degraded — not dead, just running out of steam early. what happens is the remaining devices compensate a bit so you get output, just not full output, and the rig has no idea anything is wrong so no fault code. icom's protection is pretty good at catching hard failures but a soft degradation like that it kind of just rolls with.

before you go pulling transistors though id check the bias voltage on the PA stage first. there's a trimmer in there and if someone fiddled with it previously trying to fix something else you might just need to readjust it back to spec. the service manual has the procedure, you'll need a wattmeter and a bit of patience. if bias is way off that could explain the low output without any dramatic failure mode. worth checking before ordering parts.

check if the previous owner ever ran it into a bad antenna situation or had an SWR event. i bought a 706 once that had the exact same thing going on and it turned out the guy had melted something in the drive section not the finals. the finals were fine but something before them was limiting drive and the whole chain just ran at reduced power. wasnt obvious at all looking at the board.

also just curious did you try doing a full factory reset through the menu? not just reflashing the firmware but actually wiping the settings. sometimes the power output calibration table gets weird and a reset at least rules that out as a variable before you start poking around inside.