so this has been driving me nuts for about two weeks now. picked up an 857d from a silent key estate sale, guy's family said it worked fine but honestly who knows. on VHF and UHF it hits full power no problem, measured it on my wattmeter. but on HF it just kinda... limps along. im seeing maybe 8-12 watts depending on band when it should be doing 100. audio receive sounds fine, SWR readings look normal, ALC seems to be doing something weird though — it's jumping around when i key up even into a dummy load.

already reseated all the connectors i could find and reflowed a couple joints that looked sketchy on the PA board near the finals. no change. pulled the driver transistors and they test okay on the bench, or at least they arent shorted. not sure if im missing something obvious here. anybody been inside one of these for a similar issue? wondering if it's the pre-driver stage or something further back in the chain before it even gets to the finals.

the ALC jumping around on a dummy load is a pretty good clue honestly. on those rigs if the ALC line has a bad solder joint or a leaky cap in that feedback loop it'll throttle the output even when theres no reason to. theres a couple electrolytics near the ALC circuit on the RF unit board — i think its C1045 or somewhere around there, dont quote me on the exact number — that are known to go soft on older units. worth pulling them and measuring ESR if you have a meter for it rather than just checking capacitance. i chased a similar symptom on an 897 for forever and it turned out to be a cap that read fine on capacitance but had terrible ESR and was basically acting like a resistor at audio frequencies.

also double check your PA bias voltage, theres a trimmer for that and if its drifted low youll get exactly what you're describing — everything looks alive but power is down across HF only.

had basically the same thing happen to mine after i dropped it, don't ask. turned out one of the shield cans on the RF board had gotten slightly bent and was intermittently grounding something it wasnt supposed to. probably not your issue since yours sounds more consistent but worth just eyeballing everything carefully with good light before you go chasing caps. these rigs are packed in there pretty tight and stuff moves around.