so ive been chasing this one for a while now and its driving me crazy. my 7300 works perfectly when i first fire it up, great receive, output looks fine on the wattmeter, everything normal. but somewhere around the 15-20 minute mark the receive just drops into the floor. like S0 on everything, even strong locals that i know are pumping out 50+ watts. transmit still seems okay from what i can tell but receive is essentially dead.

if i shut it down for 10-15 minutes and let it cool off it comes back fine and the cycle starts again. ive had the lid off and nothing looks obviously fried, no bulging caps that i can see, and the finals look okay visually. my first thought was a bad solder joint somewhere that opens up when the board expands from heat but i havent been able to find anything with a cold spray yet. anybody dealt with something like this on a 7300 or similar icom? im wondering if its worth sending to icom or if this is something a reasonably competent home tech could track down

that cold/heat cycle symptom is almost always a solder joint or a component that's drifting way out of spec when it warms up. the cold spray method you mentioned is the right instinct but you kinda have to be systematic about it — section by section, give it a minute to see if receive comes back before moving on. on the receive side of a 7300 i'd be looking hard at the front end stuff, the preamp transistors and anything around the roofing filter area. there's also been some talk on the icom groups io about a specific cap near the RF board that causes thermal drift issues on some units but i don't remember the exact reference designator off the top of my head.

honestly if you're not super comfortable poking around in there while it's running (and you shouldn't be with mains connected to the PA section) it might be worth the icom service depot fee just for peace of mind. they're not cheap but they'll at least give you a proper diagnosis. that said a lot of guys have fixed exactly this kind of symptom themselves with a good magnifying glass and a rework station.

had something weirdly similar on an older 746 pro, not a 7300 but same kind of symptom. turned out to be a tiny crack in a trace on the RF board that you genuinely could not see without like 10x magnification. only showed up under load and heat. ran a jumper wire across it and its been fine for two years since. might be worth checking your boards really carefully around any mounting points where the board flexes a little when things expand.