so this has been driving me nuts for about two weeks now. my IC-7300 suddenly started putting out maybe 20-25 watts max when it should be doing 100. nothing changed as far as i know, was working fine one day and then the next time i sat down to operate it was just weak. ALC looks a little weird on the meter too, kinda jumpy when it shouldnt be on a steady carrier.

ive already checked the obvious stuff — power supply voltage is solid at 13.8v under load, coax and connectors look fine, tried a dummy load and same issue so its not the antenna. SWR is reading normal when i do have a signal going out. the radio doesnt get unusually hot or anything and there are no error codes showing up on the display.

im wondering if its a PA transistor starting to go or maybe something with the ALC circuit itself feeding back wrong. anybody dealt with this on the 7300 specifically? i dont really want to ship it to a service center if i can avoid it but im also not gonna dig into the finals without knowing what im looking at first.

had almost the exact same thing happen on mine about a year ago. turned out to be one of the RD70HVF1 finals was getting weak, not fully dead but just degraded enough to drag the output down. the ALC behavior you describe matches up too because the radio is basically trying to compensate and the loop goes a bit haywire when one device isnt keeping up with the other.

before you pull it apart though, check your mic gain and the RF power knob settings in the menu, i know it sounds stupid but ive seen people chase hardware faults for days and it was a menu setting that got bumped. if those are all correct and you're still at 20-25w on a dummy load across multiple bands, yeah id be looking at the PA stage. Icom's service manual for the 7300 is floating around online and its actually pretty readable, bias adjustment procedure is in there too which you might need after swapping transistors if you go that route.

not sure if this applies but i had a weird low power issue on a different radio that ended up being a cold solder joint on the driver stage, not even the finals themselves. symptoms were almost identical to what you're describing. worth a look under magnification if you have it before assuming its the transistors, saves you buying parts you might not need.