so this has been driving me nuts for about two weeks now. buddy of mine handed me his 7300 to look at, says it just stopped putting out power one day. no smoke, no obvious trauma, just keyed up and noticed the watt meter wasnt moving. receives perfectly fine, all bands, sounds great on rx. but hit the PTT and you get nothing. ALC meter doesnt even twitch.

ive already checked the obvious stuff — antenna port is fine, tried a dummy load, RF output setting is maxed, speech processor is off. internal ATU is bypassed. firmware is current. swapped mics. still nothing.

i cracked it open and visually everything looks okay, no scorched components that i can see around the PA section. havent done any actual probing yet because i wanted to see if anyone else has run into this before i start poking around. is there a known weak point on these for TX failure or am i looking at a full PA board swap?

had something similar on a friends 7300 last year. first thing i'd check before assuming PA is dead is the TX inhibit line — there's a protection circuit that can latch up after a high SWR event or even just a firmware hiccup and it just silently blocks TX. connect it to a PC, pull up the diagnostic mode in the menu (hold down the menu button on boot if i remember right, might be slightly different on newer firmware) and see if theres any fault flags sitting there. also check that the ACC socket on the back hasnt got something weird happening on pin 3, external TX inhibit can come in that way and people forget they had something plugged in there six months ago.

if none of that pans out then yeah you're probably looking at Q1010 or one of the driver transistors upstream of the finals. the 7300 PA section isnt terrible to work on but you really want the service manual before you start probing around in there. icom's SM is actually decent for this rig.

check the mic connector wiring before you go too deep into the board. sounds stupid but ive seen people rewire a mic plug wrong and the PTT line never actually closes properly — radio thinks it's transmitting internally but the whole chain never kicks off. you said you swapped mics, did you verify both mics actually work on another radio? also is the fan spinning up at all when you key it? on mine the fan kicks on pretty much immediately when TX is active, if thats not happening either something upstream of the PA is just completely not initiating the TX sequence.