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Re: New QMX Rev 3 / High Band - Holiday Project - Success!!

 

Hi Stan, Hi All,

here a success message.
After yesterdays experiment running QMX direct from 3.3V and getting confirmed? CPU and rest of 3.3V Rail OK, I spend all evening/night rechecking QMX? over and over again.?
Some helpful document (from Hans Email) on the boot process that I checked along:?

All looked perfect, no issue found. (Yes: I know the power plug issues etc, but have correct size)

So today I have stolen the 3.3V SMPS module of my QMX Rev 1 Low Band and transplanted it to QMX Rev 3 High Band: My Kids only have license 10m / 2m / 70cm.

Rechecked again everything and carefully powered up with strict current limitations 7V 200mA: Success, no current limitation!?
Did HW checks on Terminal: all OK. Slowly increasing power as more tests passed. Run a first FT8 QSO and put some CQ's in CW out all OK so far. Will check it the next days.

Conclusion: All perfect so far. Just had a broken 3.3V SMPS board in the kit to replace.? Have build so many of Hans Kits, never had issues in past, this is still a very good quality in average.

VY 73 DE Thomas - DJ1TF - JJ1QPB




Am Mo., 6. Jan. 2025 um 08:09?Uhr schrieb Stan Dye via <standye=[email protected]>:

It is also safe to use one of the 3V smps cards from either of your other two kits, now that you have shown the main board does not have a 3.3V short.
After doing that, and verifying no problems, you can also remove D109 from the bad 3.3V card, and go ahead and use it without D109 to make sure that is the problem.? It will function fine without D109, but that leaves you vulnerable to a new fault causing damage on the main board.? So don't operate with it that way for long periods.? But it would give you confidence that replacing D109 would make it serviceable again.
The most common causes of D109 failure (that I am aware of) is accidental momentary shorts of 12V or 5V rails to 3.3V during assembly or handling with power on - the minimal clearances within make this easy to do.? Also please check your power plug connector from your power supply, that it is 5.5/2.1, not the similar 5.5/2.5, which looks almost the same, but has a larger diameter hole for the power pin, and doesn't contact properly.? Some have reported D109 failures that seem to be traced to such a connector - which will work most of the time, but actually can give many very short power on/off spikes when it is moved, since it 'bounces' in the ill-fitting contacts.
Stan KC7XE
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