My first post to the group never arrived, so I'll try again today.
I bought and assembled a QMX a couple of weeks ago to beacon in the Eclipse challenge. It arrived in just a few days and worked fine at first power-up. I brought it in to the HQ of the "local amateur radio manufacturer" to show it off and they were suitably impressed, as expected.
One tech there connected the QMX to a KX2 battery (12.5V) and was investigating the menus, hand-holding the radio with the battery dangling. It shut off by itself. He turned it back on and wiggled the 2.1mm connector. It shut off again.
Now it will not turn on.
I was standing right there watching, so I know this is how it happened. Either I am unusually "lucky" or this problem is not as rare as has been postulated.
The 5.6V zener was blown and was replaced. Now the 3.3V supply is clamped to about 1V and the 5V supply does not start. Thermal camera images show one of the QFPs getting warm while the rest of the board(s) are cold. The boards only draw current while the power switch is held closed, and the display is dark. Radio is completely unresponsive.
I like the idea of trying separate CURRENT LIMITED 3.3 and 5V power supplies to test the QMX after replacing the bad QFP. Anything else I should watch out for?
Meanwhile, I purchased another QMX board set. It also arrived quickly and was immediately built--the second one is so much easier than the first. It also worked the first time and survived 12 hours of WSPR beaconing, much of which was transmitting at nearly 100% duty cycle (in every WSPR cycle), during the eclipse. I wound this one for 9V (the first was wired for 12V) and has only been used with a current-limited supply. It has QSOd on CW and FT8 besides its time on WSPR.
FWIW, I'm seeing what appears to be a firmware bug not yet mentioned on this list. WSPR transmissions are squelched if a GPS is connected--whether or not CW Protection is enabled. This is with 1.000.10 firmware.
Anyway, any advice for troubleshooting my dead boards is welcome.
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73 de Bob, K6XX
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73 de Bob, K6XX
Bob Wolbert, K6XX