so this has been driving me crazy for the better part of two weeks now. my IC-7300 will key up fine, ALC meter moves, the PA temp reading looks normal, everything looks like its transmitting but the wattmeter on my dummy load is flatline. doesnt matter what band, doesnt matter what mode. i swapped the coax thinking maybe i had a bad connector somewhere and that wasnt it.

i pulled the top cover off and poked around a bit with the scope. drive signal looks like its making it to the driver stage okay as far as i can tell but im not super confident reading that board — icom doesnt exactly hand out the schematics for free. i did notice one of the small electrolytics near the PA section looks a little domed on top but im not sure if thats actually the culprit or just normal aging. radio is maybe 6 years old and lived most of its life in a pretty humid shack.

has anyone dug into one of these for a similar symptom? wondering if this is a known failure point or if im chasing something weirder. happy to desolder and test components i just want to have some idea what im actually looking for before i start pulling things.

that domed cap is almost certainly your problem or at least one of them. i had a 7300 come through here with nearly identical symptoms and it ended up being two caps in the PA bias supply that had gone high ESR. once the bias rail sags the finals just sit there doing nothing and the drive signal goes nowhere. you can check them in circuit with an ESR meter if you have one, though honestly at that age in a humid environment id just replace the whole cluster around that area while youre in there. nichicon or panasonic FM series, dont cheap out on the replacements.

the icom service manual for the 7300 does exist, it floats around if you know where to look, might help you trace the bias circuit before you start swapping things randomly.

yeah domed cap is a red flag for sure but also worth checking — did you verify the finals themselves arent blown? if one of them went and took out a gate resistor you can have that exact symptom where everything looks fine upstream but nothing comes out. the 7300 uses RD70HVF1s in the final and they can fail quietly without any drama, no smoke no bang just... nothing. easy enough to check with a meter out of circuit. pull them, check gate to source and drain to source, should be obvious if ones shorted.