so this has been driving me nuts for about two weeks now. picked up an 857D off a silent key estate sale, price was too good to pass up even knowing it might need work. guy's family said it was working fine but who knows how long it sat in that garage.

anyway when i got it home and fired it up the S meter just sits at zero, no noise floor, nothing. squelch all the way off and still dead silence. but here's the weird part — i can key it up and my other radio hears it just fine on the other side of the room, so RF is getting out apparently. tried it on multiple bands, same thing across the board. also tried different antennas and a dummy load just to rule that out.

i pulled the covers and dont see any obvious damage, no burnt components or anything that looks fried. voltages on the main board look reasonable to me but i only have a basic DMM so im not catching anything subtle. anyone dealt with this specific failure mode on the 857? wondering if its the RX frontend or something in the IF chain. service manual is not super helpful for actually diagnosing this kind of thing, at least the way i read it.

had almost the exact same thing on an 857D a few years back. ended up being a bad relay — the one that switches between TX and RX path. it was getting stuck in the transmit position so RF was going out fine but on receive the signal path was just broken. you can sometimes hear the relay click when you key up and unkey, so listen for that. if you dont hear it or it sounds weak/sticky that's probably your culprit. Yaesu used some relays in that era that dont age well especially if the radio sat unused for a long time.

the part itself is cheap, maybe a couple bucks if you can find the exact spec, but getting to it is a bit of a pain in that chassis. i think mine was on the PA board area if i remember right, been a while. worth checking that before you go chasing anything in the IF strip which would be a much bigger rabbit hole.

also check if someone messed with the IPO or attenuator settings, i know thats probably obvious but ive seen people waste days on stuff like that lol. probably not your issue if its totally dead though yeah. the relay theory sounds right to me, that or the antenna relay on the RF board. good luck with it, 857s are worth fixing if you can get it sorted.