so ive been sitting on doing the mars/cap mod on my ft-857d for like two years now and finally just did it last weekend. honestly wasnt as scary as i thought, just a couple jumpers on the main board. took maybe 20 minutes once i had the service manual pulled up on my laptop.

what i actually wanted to talk about though is while i had the thing apart i noticed the stock fan barely spins during normal operation and the finals get pretty warm. i ended up swapping in a slightly higher CFM fan i pulled from an old PC and wired it to come on at a lower temp threshold. not elegant but seems to work. running digital modes for extended periods used to make me nervous but now it stays way cooler.

anyone else messed around inside the 857 or similar rigs? curious if the fan mod is a known thing or if im just reinventing the wheel here. also did the mod affect anyones TX audio noticeably — i feel like mine might be slightly different but could just be placebo

the fan thing is pretty well documented actually, there's a thread on eham somewhere from years ago where a guy measured temps on the finals with the stock fan vs a better one and the difference was pretty significant under sustained load. you're not crazy. for digital modes especially PSK or JS8 where you're sitting at high duty cycle for a long time it genuinely matters. i did something similar on my 7100 though the internal layout is obviously different. the stock thermal management on a lot of these japanese rigs from that era is kind of "good enough for voice" and not really designed with WSPR or FT8 in mind, that stuff just wasnt as common when they were being designed.

as for TX audio after the mod, i didnt notice anything on mine but i also run an external mic processor so i probably wouldnt. worth throwing a recording into audacity and comparing to something before if you saved anything.

cant speak to the 857 specifically but i did the same mod on an older 897 and honestly the main thing i noticed was just peace of mind more than anything measurable. warranty was already long gone on mine so that wasnt a factor lol. the fan swap sounds smart though, im paranoid about cooking finals on digital.