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Hi?
I have assembled a QMX and a QMX+ and they suffers from the same failure!

I was able to load firmware into both of them.

Then they don't boot at all!
When pressing the poweron they both try to draw more than 1A at 8.8V (and no display backlight).

All the smps-boards was tested and working in a rev.1 QMX.

Strange I have the same problem in both a QMX and a QMX+!

What to do next ????

de oz9ny, niels

On Sat, Jun 22, 2024 at 04:19 PM, Niels Jalling wrote:

All the smps-boards was tested and working in a rev.1 QMX.

Strange I have the same problem in both a QMX and a QMX+!

Niels,

so you produced the same failur in both, but where???
Or did you use for both the same power cable, maybe a broken one?

When pressing the poweron they both try to draw more than 1A at 8.8V

If not the cable please limit the current to around 250 mA for more tests.

But before testing voltages check resistance from VDD to GND and VCC to GND with all the subboards removed from the mainboard. The linked document contains a link to a sketch to find the signals on the QMX. For QMX+ the signals are marked in the assembly manual.
All these values should be around 10 kOhm or more. If only a few ohms something is wrong related to the VDD rail and / or the VCC rail.

Please read this QRP Labs Wiki document about the start, section "switch on power".
There you find information about some signals and voltages to search for the problem.

73, Ludwig