so i picked this up at a hamfest a few weeks ago for basically nothing, guy said it worked but he hadnt used it in a while. got it home and yeah it receives fine, sounds great actually, but when i key up im only seeing about 20 watts on my wattmeter on any band. the meter on the radio itself is reading what looks like normal power but clearly something is off.

ive been poking around and the finals look okay visually, no obvious burn marks or anything cracked. i did notice the driver board looks a little crusty around one of the caps near the back corner but i dont know if thats related. voltage at the supply is solid at 13.8v under load.

anyone been inside one of these? im wondering if its a bias issue on the finals or maybe those output caps have gone south. or honestly could be something dumb like a bad connector. thought id ask before i start shotgunning parts at it.

yeah the 757GX is notorious for the driver transistors getting weak before the finals actually die. a lot of times the finals test okay on a DMM but they're just not getting properly driven anymore. worth checking the bias on the driver stage first before you go touching the PA board. there should be a trimmer on the driver board and if the previous owner ever messed with it or if a cap leaked near it thats almost certainly your problem.

also those electrolytics on the driver board do go bad, especially if it sat for years. if you see any that look crusty or have residue around the base just replace them all while youre in there, theyre cheap. i had a 757 a few years back that was doing exactly what you describe and it ended up being a single 100uf cap that had drifted way out of spec. swapped it out and it was back to 100 watts no problem.

check the ALC line too. sometimes something upstream is telling the radio to back off power and it just stays stuck there. had a similar thing with a different rig and spent way too long on the PA before realizing the ALC was being pulled down by a bad connection at the mic jack of all places.