Some learnings and a success (eventually, with another build)
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Finally had time to wrap up this topic, so I will provide an update for anyone facing the same issues as I did. Hopefully this helps some poor soul going through what I did.
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My initial build had 2 solder joints that needed touching up: an SMPS GND pin on the main board, and one pin on the LCD potentiometer. Unfortunately while trying to debug the GND connection on the SMPS while powered on, I believe I may have shorted some connection with one of the DMM probes, which caused damage to ?one of the diodes on the board. This resulted in the radio not powering up at all after that. Symptoms included popping in the headphones while the power button was pressed, rig powering on only for the duration while the button was kept down and then powering off immediately on releasing it.
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I decided to replace the SMPS boards. If I'm not mistaken the only SMPS available for purchase separately were for REV 1 boards, so because of that plus an abundance of caution I ordered a new QMX kit, with the idea to do a better job on a second try.
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Today I started building the second kit and a few hours later I got to the step where you plug it in and hope for the best. It connected to the computer, I loaded the firmware and it rebooted to a fully working rig! I've yet to test it for power output because my antenna only has an SO-239 connector and I haven't got any BNC lying around, but I'm glad the learnings from the first build transferred over to a successful one. And now I have spare parts too in case I need that.
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My takeaways from this whole experience are:
- solder joints can look perfect yet still not make contact
- wielding the DMM probes while the radio is powered up is a bad idea most likely
- this is not an easy kit to build (today I had an accidental soldering iron slip which put solder across 3 pins of a close proximity IC. Almost had a heart attack but after 15 minutes of struggling with the iron and a sewing needle, I managed to break the short without damaging anything else)
- despite it being challenging, after the first try you really can go full speed on building this kit. I recommend you keep going even if at first it might have been a failure
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Many thanks to all those who shared their advice and thoughts in this thread, and despite me not having proper equipment for many of the testing procedures suggested, they've all helped me sort out what to look for in my second build, even before applying power.
