so ive been chasing this one for a few weeks now and its driving me nuts. my 7300 started dropping output gradually, first i thought it was an ALC issue or maybe i had the RF power knob turned down (yeah i checked, i'm not that far gone yet) but even with it cranked all the way i'm seeing maybe 18-22 watts into a dummy load. SWR is flat, the rig doesn't throw any error codes, TX indicator lights up fine, everything looks normal except the power output is just... sad.

i've already reseated the connectors i could get to without a full teardown, checked the PA heatsink and it's not hot at all which is kind of what worries me actually -- like if one of the finals was thermally shutting down that would make sense but it never even gets warm. my dummy load is a bird 43 so that's not the problem.

anyone dealt with this before? i'm wondering if it's the driver stage or maybe a bias issue. dont really want to send it to icom if i can avoid it, the turnaround has been terrible lately from what i hear.

bias drift on one of the finals would be my first guess honestly. the symptom you're describing -- gradual power loss, no thermal shutdown, no error codes -- that pattern usually points to a transistor that's still partially functional but the bias point has shifted. the 7300 uses RD70HHF1s in the PA stage if i remember right and they're not exotic but they do drift over time especially if the rig ever ran hot for extended periods.

before you do anything drastic i'd pull the covers and measure quiescent current on the PA with no RF drive. there are a few guys on the icom repair forums who've documented this exact fault and most of them found one device biased way off from spec. sometimes you can trim it back if the adjustment is still in range, sometimes the transistor itself is just weak and needs replacing. either way it's not a terrible job if you're comfortable with RF power stages, just be careful obviously, those drains can bite you even at idle.

also worth checking the ALC voltage at the PA input with a scope while transmitting -- if the ALC is clamping harder than it should that's a different but related problem and it would show up pretty clearly.

had almost the exact same thing happen on mine maybe a year ago, turned out to be a cracked solder joint on one of the connectors going to the PA board. not visible to the naked eye, had to use a magnifying glass under good light to find it. the joint looked fine but under load it was making intermittent contact and the rig was just folding back the power to protect itself even though it wasnt showing a fault. re-flowed it and went straight back to 100w.

might not be your issue but worth looking before you start suspecting the transistors themselves.