so this is getting frustrating. had my 7300 back from the shop in march after the finals went out, they replaced both MRF101AN transistors and said it was good to go. well its doing it again. same symptoms — output drops to basically nothing, SWR alarm goes off even into a dummy load, and i can smell something faintly when i key up. checked the dummy load and its fine so thats not it.

the tech who fixed it the first time said maybe i had a momentary high SWR event that killed them but i run an LDG tuner inline and ive never seen it go above like 2:1 for more than a second. im starting to think theres something upstream thats causing a voltage spike or maybe the driver stage is putting out too much and stressing the finals. i dont really have a good way to check driver output without the right equipment but wondering if anyone else has seen this pattern with the 7300 specifically.

also worth mentioning i run it at 100w most of the time and its on a decent regulated supply, 13.8v dead stable. so its not a voltage issue i dont think. would love to hear from anyone whos dug into one of these at the component level.

yeah ive seen this exact thing happen to a buddy of mines 7300. turned out the problem wasnt the finals themselves but a failed bias adjustment — the driver was running hot and slowly cooking the finals even at normal power levels. the shop fixed the symptom but not the cause basically. if you can borrow a spectrum analyzer or even just a current probe you might be able to see if the quiescent current on the final stage is running higher than spec between transmissions. icom specs that out at a pretty specific value in the service manual and its worth checking before you throw more MRF101s at it.

also check the low pass filter section, one of the caps in there can go leaky and cause weird reflections internally. its a long shot but ive seen stranger things. honestly though if the same shop is fixing it twice without finding root cause id probably look for someone who specializes in Icom gear specifically.

not to derail but this is why i always bench test after any final replacement, like actually run it at full power into a proper dummy load for 20-30 minutes and watch the current draw the whole time. if the bias drifts as it heats up you'll see it. sounds like whoever did the repair just swapped parts and called it done without really digging in.