so this has been driving me nuts for about two weeks now. my 7300 started acting up after a pretty bad storm came through, nothing got hit directly but there was a lot of static and i had been running it during some of the lead-up before i realized how close things were getting. anyway ever since then the rig will only push maybe 20-25 watts on HF no matter where i set the power control, used to do a solid 100 no problem. TX audio sounds fine from what people tell me, receive seems totally normal, SWR reads fine on a dummy load so its not the antenna side.

ive already reseated all the internal connectors i could get to without going too deep, checked the PA bias voltage which looks a little low honestly but im not 100% sure what it should read on this specific model. ALC looks like its not going crazy or anything, sits pretty normal during TX. i really dont want to send it in to icom if i can avoid it, the turnaround time from what ive heard is brutal right now. anyone dealt with low power output on one of these that wasnt just the drive setting being messed up or ALC going haywire?

PA bias being low is probably your smoking gun honestly. on the 7300 theres a trimmer for the final PA bias and if it drifted or got nudged somehow you'll see exactly what you're describing — rig acts totally normal otherwise but just cant make full power. the service manual has the procedure for setting it, you need to look for a specific idle current spec i think its around 600mA total for the finals but dont quote me on that, definitely pull the actual manual. a near-miss from lightning or even just a nasty transient through the power line can absolutely cause a trimmer to drift, ive seen it more than once.

before you go poking at bias trimmers though make sure you rule out the driver stage, if the driver board took a hit the finals could be getting underdriven and show the same symptoms. you can check drive level at the input to the PA board if you have a decent scope. not saying it is that, just worth checking before you start tweaking bias and chasing your tail.

had almost the exact same thing happen to my 7300 last year, different cause but same symptom. mine turned out to be one of the finals was partially blown, like it wasnt totally dead but it wasnt pulling its weight either. rig still transmitted fine, sounded ok, just low power. had to send it in because i wasnt comfortable replacing finals on that board myself, the SMD work on those things is not fun. just something to keep in mind if the bias adjustment doesnt fix it.