Florin,
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? Looking over this thread you noted that your VDD - GRN resistance reading is 55 Ohms on the main board (should have a reading of plus 2k Ohms).? ?This would concern me and would lead me to believe that your 3.3v rail is drawing too much current.? ?Possible not fully reaching 3.3v when commanded by your MCU after initial power up sequence.? ?I believe that is why you can only keep your QMX powered on by holding down the power button.
? I strongly suggest that you stop the practice of holding in on the power button as this could be damaging a component(s) that is the cause of the low Ohm reading.? If could be a shorted cause by a solder shorted bridge.? ?I am glad to read that the QMX is responding the way you described as this mean that that the MCU is still working (If MCU burn out BIG NO GOOD, but your is still working).
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?My suggesting:
1. DO NOT APPLY any power to your QMX anymore.
2. Continue Problem Solving the low OHM reading on the main boards VDD - GND issue.
3. Looking for possible bad solder bridges.?
4. Damage components on the 3.3v rail that maybe shorting the 3.3v rail to ground.? (Still check by using you DDM on Ohms setting.? ?No Power applied to your QMX- No Battery or Power Bank Plugged to it).
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Your QMX has an issue on the 3.3V rail per your posting of you what you had when you posted your VCC-GND and VDD-GND results.
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? To keep from any further damage to you QMX- DO NOT APPLY POWER TO YOUR QMX (Until you resolve the LOW OHM READING on your VDD-GND).? ?Sorry I just want to make that very clear, so you don't lose your QMX due to burning out a part that is not easily obtainable (The MCU with Hans' encrypted Boot Loader.? They are not sold currently as a replacement part).? (@ Hans,? I understand why, to protect your intellectual property).
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?You can search this forum and find how to safely apply power to the QMX to limit Voltage and Current so to not to damage components to help track down the culprit with this type of issue.? But from what I read it sounds like you may not have a power supply with these capabilities.? ?Forgive me if I assume wrong.
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? Hope this helps and good luck with your build.
73 KQ4DTX
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