so ive been sitting on doing the mars/cap mod on my FT-857D for like two years now, always nervous about voiding the warranty (which is already long gone lol) and just general anxiety about poking around inside a radio i actually use daily. finally bit the bullet last weekend.

for anyone who hasnt done it, its pretty straightforward once you get the thing open — theres a diode on the main board you either remove or short depending on what you want to do, the Yaesu service manual has the details. took me maybe 45 minutes including the time i spent second guessing myself and looking at the board with a flashlight trying to figure out which one was D4003 or whatever it was.

anyway the reason i did it wasnt just for extended TX, i mainly wanted to mess with the receive on some of the utility stuff below the ham bands. and honestly its working great for that. also been thinking about doing the internal fan mod because this thing runs hot when im doing digital modes for more than like 20 minutes. anyone done the fan upgrade on one of these? ive seen a few writeups but theyre pretty old at this point and im not sure if the links to the replacement fans are still valid.

yeah i did something similar on mine probably three years ago. the fan mod is worth doing if you're running PSK or FT8 for any length of time, the stock fan is pretty anemic. i ended up just sourcing a 12v fan from an old PC power supply that had the right form factor, wasnt an exact match for CFM but its quieter and moves more air so thats a win. the only annoying part was figuring out the connector, i think i just cut and spliced rather than trying to find the exact JST header.

one thing i did notice after the TX mod is that ALC behavior felt slightly different on some frequencies outside the ham bands, not sure if thats just in my head or an actual thing. on the ham bands it behaves totally normally. might be worth keeping an eye on your power output if youre transmitting anywhere outside normal freqs, not that youre doing that of course

the fan writeups on eham and some of the older groups.io archives should still have part numbers. i bookmarked one a while back but cant find it now, typical. what i do rememeber is someone used a Noctua NF-A4 which is obviously overkill but dead silent and supposedly fits with some bracket modifications. seemed like a lot of work to me but if you care about noise floor during receive it might matter.