I built a midband QMX a couple months ago; it worked fine for a solid handful of QSOs and many hours of use in code practice mode.
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I was in the process of testing a newly built manual antenna tuner. I hit the key to transmit and the SWR protection kicked in, exactly as it should. I turned off the QMX intending to power cycle it to clear the SWR protection but when I tried to turn it back on, the screen didn't turn on, I heard a strange buzzing through the headphones, and I smelled smoke.
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I opened up the case and tried again to turn it on under closer inspection. I determined that Q108 was the component that was smoking (or at least the component that produces smoke first when power is applied and the left button is held to turn the rig on). Additionally, L101 seems to have a ring of residue or crust (see photo) which is not present on L102. I don't remember seeing it when I built the kit, but I can't be 100% sure that it wasn't there before.
Has anyone else experienced a similar failure condition?
Would there be any harm in disconnecting the 5v SMPS board and powering up the QMX without it to inspect the status of the processor via the serial interface?
What other troubleshooting steps should I try next?
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Thanks for your time and 73,
Hudson, KL4LJ
