so this has been driving me nuts for about two weeks now. my 7300 started acting up during a contest — was running fine at 100w then suddenly power dropped to like 8-10 watts and the ALC was pegged way into the red. thought maybe it was a software glitch or something so i rebooted it, no change. tried different bands, same thing across the board which made me think probably not a filter issue.

checked the antenna, SWR was fine on the dummy load too so its not a reflection problem. pulled up the radio's internal power meter and its definitely not putting out anywhere near rated power. the receive side seems totally normal which is kind of confusing me — like why would RX be fine if the finals were actually gone.

anyone dealt with this before? im wondering if its the driver stage rather than the finals themselves but honestly i havent cracked the lid yet because im a little nervous about digging into a radio this new. its about 3 years old and out of warranty obviously. should i just send it to icom or is this something diagnoseable at home if you have a decent DMM and some patience

yeah the RX being fine is actually consistent with finals or driver issues, those circuits are pretty separate on the 7300. the fact that it went south mid-contest makes me think thermal — either a transistor that was already marginal finally gave up, or a solder joint that opens up when hot. i had something similar on an old 746 years ago and it turned out to be a cracked solder joint on one of the driver transistors, reflowed it and it came back to life.

before you do anything else though, check if Icom has a service center near you. the 7300 schematics are available if you search around and the finals are RD70HVF1 MOSFETs if memory serves, not super expensive, but pulling and replacing them without knowing for sure thats the problem is a bit of a gamble. honestly if you're not confident with RF stages id say at least get a second opinion from someone local who works on radios. ALC pegged hard like that usually means the radio is trying to compensate for something that isnt there anymore.

dont rule out the PA bias drifting — ive seen that cause exactly what youre describing. the 7300 has a bias trimmer and if it walks off for whatever reason the output just falls off a cliff. might be worth looking up the service adjustment procedure before you start swapping parts, could save you some money if thats all it is.