so i've had this 857D for probably 4 years now and always ran it stock because i was kind of nervous about opening it up. finally bit the bullet last weekend and did the mars/cap mod to open the TX range and also swapped out the stock fan for a quieter one while i had it apart.

the fan swap was honestly the best thing i ever did to this radio, that stock fan is obnoxious and the replacement i got off amazon (some 12v noctua-style thing, cant remember the exact part number) is dead silent and seems to move plenty of air. ran it at 100w for like 20 minutes on FT8 and it barely got warm.

the TX mod itself was straightforward, just moving a diode, but i was sweating the whole time because the board is packed in there pretty tight. no issues though and it came right up on the first power-on. just nice to have the flexibility even if i never actually use the extended freqs.

anyone else done any other worthwhile mods to the 857? ive seen some stuff about firmware but wasnt sure if it was worth it or if theres anything else that actually improves day to day usability

the fan mod is legit one of the best bang for buck things you can do on those radios. i did something similar on my 897D years ago. the thermal design on the stock units is just kind of lazy, they clearly just spec'd whatever was cheapest.

for other mods worth doing — if you're doing a lot of digital modes, some people replace the electrolytic caps on the audio board, especially if the radio has some age on it. mine had a slight hum issue on TX audio that turned out to be a cap starting to go. fixed it and cleaned everything up nicely. not a sexy mod but useful if you notice any audio weirdness.

also worth checking is the TX EQ settings in the menu if you havent already, not a hardware mod obviously but the default voice audio on those is pretty nasal and spending 10 minutes tweaking it makes a real difference on SSB. i know thats not really what you asked but figured i'd mention it

yeah the mars mod on yaesu stuff is pretty much a rite of passage lol. did mine day one honestly. the only thing id add is double check your power output on the expanded segments because sometimes it drops off noticeably outside the ham bands, mine was only doing like 60-65w at the edges which was fine for my purposes but worth knowing.