so this has been bugging me for a couple weeks now. my 857 is doing something weird where on 40m i'm only getting maybe 20-25w out when i've got it set to 100w. every other band is totally normal, checked it with my wattmeter on 20, 15, 10, even 6m and they're all within a few watts of where they should be. 40 is just... sad.

i did the usual stuff first, checked the antenna, swapped cables, ran it into a dummy load to rule out the feedline. still the same deal. SWR on the meter looks fine so its not folding back from that. ALC is behaving normally as far as i can tell.

i'm thinking it might be the low pass filter board or one of the finals is getting flaky on that band specifically but i honestly dont know where to start with it. anybody pulled one of these apart for something like this? i have the service manual but some of those board layouts are a headache to trace through.

had almost the exact same thing on my 897 a few years back, different radio i know but the architecture is pretty similar. turned out to be a cold solder joint on the LPF switching relay for that band. the relay itself was fine but one of its legs had a hairline crack in the solder that was just barely making contact. you could wiggle the board and the power would jump around. worth getting in there with a loupe and going over the relay connections on the 40m LPF section before you go chasing finals. reflowed it with a iron and it's been solid since.

if you do get in there, check the band switching transistors too while you have it open, they're cheap and easy to swap and they do fail on these sometimes.

could also just be one of the driver transistors starting to go, not necessarily the finals. i've seen these come in where only one or two bands are affected and it traces back to the driver stage getting weak. finals usually either work or they dont, a partially bad driver can give you this kind of weird band-specific low output. just something to check before you go buying finals which are not cheap