so this is driving me nuts. picked up an 817 from a local silent key estate sale, guy's family had no idea what they were selling so i got it cheap but obviously theres a reason it was sitting on the shelf. fires up fine, all the menus work, i can key it up and the ALC meter moves, even the TX indicator lights, but zero RF out on any band. tried it on HF and VHF just to rule out a band-specific issue and same thing everywhere.

already pulled the finals and they tested bad so i replaced them with the recommended 2SK2975s, resoldered everything, checked the driver stage too and that all looks okay with the signal tracer. still nothing coming out the antenna port. the SWR/power meter i'm using is a pretty decent Bird so its not a meter problem. just wondering if anyone's been down this rabbit hole before because i'm running out of obvious stuff to check and the service manual is only so helpful past a certain point.

had almost this exact thing on an 817nd a while back. turned out to be the low pass filter board — one of the relays on it had a coil that looked fine but the contacts were welded shut internally. the relay was switching but not actually connecting the RF path through. you'd never find it just probing around unless you're actually injecting signal and tracing it through the LPF section specifically. i think it was RL3 or thereabouts but honestly check the whole board, run signal in before the relay bank and see where it stops coming out. the 817 has a bunch of those little reed-style relays and they do fail, especially if the rig ever got keyed into a bad load.

also just double check your finals are actually seated right and the gate resistors on the driver didn't get cooked in whatever killed the originals. common thing to miss.

the LPF relay idea is a good shout. i'll also say — did you verify the TX path enable voltage is actually making it to the PA board? on mine there was a cold solder joint on a tiny SMD transistor near the TX/RX switching that was intermittently dropping the bias voltage and it looked totally normal visually. had to actually probe it under power to catch it. the 817 is a nightmare to work on at that level cause everything's so crammed in there but its doable if you're patient.