Hey all! Got my QMX+ rev 3 last week and have had a blast assembling it over the past few days. Finished it last night, booted just fine, and was able to tune some CW on 10m with a big grin on my face ?
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The thing of it is - after a few minutes, it froze. The LCD contrast went a bit darker, audio output stopped, and all front panel controls had no effect. Unable to power off by holding the VOL encoder, I had to cut power at the source. A short time later I was able to boot back up, browse some bands, tune some CW, and then it freezes again. Same symptoms: LCD goes higher contrast, audio stops, all controls stop, have to cut power.
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I'm pretty new to debugging PCBs but figured I'd dive in as best I could to gather some info, and here's what I've been able to piece together:
- I wired it for 12V, and based on measurements my battery was delivering consistent 12.13V
- Contemporaneous with each instance of the board freezing was a drop from 12.13V down to 12.0V
- I checked a number of the components around the PWR_ON and PWR_HOLD circuits, and no blown components
- However, the measured voltage across R105 went from ~3V (normal operation) to ~4V (frozen)
- No smells or popping sounds like components faulting/failing
- No changes to the LCD indicating on-board protections or anything like that
- Tried running 9V in case there were unobserved fluctuations in my power source, but it was the same behavior - a few minutes of normal operation, and then freezing
- measured voltage during operation was around 7-8V
I've tried connecting to the serial terminal to check the on-board diagnostics, and that seems to be the most consistent way to trigger a freeze. Without trying to connect a terminal, I can usually get about 2-5 minutes of normal operation between power cycles, but as soon as I attempt to connect the terminal, it freezes.
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Like I said, I'm new to a lot of this but eager to learn so forgive me if there's obvious debugging steps I've missed ? ??. But yeah, not quite sure where to go from here! Would greatly appreciate any help or pointers!
Michael Shiplet