so ive been putting this off for like two years but i finally cracked open the 857d last weekend to do the mars/cap mod so i can tx outside the ham bands for some emcomm stuff our group does. pretty straightforward once you find the right jumper, theres like three different versions of this mod floating around online and two of them are wrong so heads up on that. i ended up using the one from the eham thread that was posted back in 2019, worked first try.

while i had it apart i also replaced the stock electrolytic caps on the PA board because mine is an older unit and a couple of them were looking a little puffy. not catastrophically bad but enough that i didnt want to leave them in there. grabbed some nichicon fine gold series replacements, probably overkill but whatever they were cheap enough. havent done a full power output comparison yet but it definitely runs cooler which either means the caps were causing some inefficiency or im imagining things.

also re-seated the main display ribbon cable while i was at it because i had that occasional flicker thing that seems to plague these radios. that alone might have been worth opening it up. display has been rock solid for the past week of daily use.

anyone else done the AF filter mod on these? ive seen some stuff about tweaking the DSP filter rolloff but im not sure if its worth the hassle. my rx isnt bad as-is but always curious what people have actually gotten from it versus what people claim on youtube.

the AF filter mod is hit or miss honestly. i did something similar on my 897d which shares a lot of the same guts and the difference was maybe noticeable on weak SSB signals in a crowded band but nothing that made me go wow. the bigger bang for the buck on those radios i found was just spending time with the IF shift and width controls together, theres a sweet spot that most people never find because they only adjust one at a time.

good call on the caps by the way. ive got an 857 thats been sitting in a hot car mount for years and i keep meaning to check them. the puffing issue on the Yaesu PA boards from that era is pretty well documented, i think it was a bad batch of caps from the factory or maybe just the heat cycling from mobile use. either way your instinct to replace them preemptively was the right call.

whats your current antenna situation for the emcomm work, are you running it into a tuner or do they have specific resonant antennas for the frequencies you need?

which jumper location did you use exactly, J4011 or the one closer to the mic connector? i tried this on mine about a year ago and i swear i used the right one but i still had issues on 60m specifically. everything else opened up fine but 60m tx was flaky. ended up just leaving it and havent gone back in since but your post is making me want to try again