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Hello,

I've built another QMX REV1. I attached 7V-9V. When pressing the left encoder, the consumption goes up from 0 to 60mA. The consumption stays at 60mA. Conclusion: the CPU is working and pulling PWR_HOLD up.
Unfortunately, I don't get any USB connection and I couldn't push the firmware yet. With my second QMX I could compare things like the cable:
- Cable: OK

- Laptop: OK

- USB Port: resoldered a few times, no shorts visible

- VDD: OK

1. Are there other things, I can check?

2. Is there any hope, that the CPU is OK?

3. 60mA seems too low. On my other QMX I see 120- 150mA. Is this because of the missing firmware, or is this a hint to other faults?

Thanks and vy 73,
Peter DL4PJ

Hey Peter,

I recently built a qmx+ and found the the USB connection can be a bit temperamental.

I have found that if I plug the UBS connection in whilst the radio is powered, the computer doesn't 'see' the qmx.

What I do is, power on the qmx after plugging in the USB cable.

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Good luck.

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Mel. M0KMD.

Actually, I just plugged in the radio to the USB whilst it was powered up. It connected, no problems! I stand correct! It connects either way. Maybe I have a dodgy USB cable!..

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Mel.

Hi,

thanks for your answers. I can also exclude the following error causes:
- defective cable

- wrong order of powering up / connecting to USB
How much power conssumption did you have in factory state without firmware installed?
(As mentioned above, I have 60mA)

Thanks,
Peter DL4PJ

Hi Peter,

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Perhaps you need to 'force' the radio to go into bootloader mode.

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Check out page 57 of the assembly manual? ->

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Mel. M0KMD.

I've also already tried to enforce to go into the bootloader mode by bridging the two pins.
No success :-(

thanks,
Peter DL4PJ

Peter, if the power is staying on after you release the button, then your cpu is likely fine.? But yes, the current draw is too low, so something is not coming up properly.? You will need to take the bottom cover off and carefully check for things touching that shouldn't be, and inspect the bottom of the board carefully for solder flakes etc., perhaps lodged in the pins of the surface mount components.? And (while powered on, make voltage measurements at each of the connector pins for the 2 smps, which will give a picture of what is going on.??

See this recent post by Hans regarding power draw at initial turn on: /g/QRPLabs/message/138969

Thanks Stan!
With 7V input I measured the following voltages:

Correction:
JP103
1 ? +12V ? ? ? ?7.02
2 ? ADC_3V3 ? ? 1.19
3 ? LIN_REG_EN ?6.49
4 ? VDD ? ? ? ? 3.10
5 ? PWM_3V3 ? ? 0 ?
6 ? GND ? ? ? ? 0

Those voltages all look fine for a v1 QMX.?

The CPU has to be running in the bootloader to have set the PWR_HOLD signal, so it's at least partially OK.

And it won't try to start up the two smps (PWM_5V, PWM_3V3) and turn off the IC101 linear regulator (LIN_REG_EN to 0V) until after it has firmware loaded and running.

But still only 60mA and no USB drive?

You don't have a current limit set to less than about 200mA do you?

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I'm not familiar with a failure like this - maybe someone else has ideas.? It seems like the power supplies are ok and the cpu is running, but not pulling the normal amount of current.? Normally we see excess current being drawn.

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One thing I would do is check for any SMD component that may have been dislodged from the board while soldering, but I'm out of other ideas for now.

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Good luck, Stan

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Thanks Stan for all your help.

"But still only 60mA and no USB drive?"
Yes: only 60mA and no USB

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"You don't have a current limit set to less than about 200mA do you?"
I've turned it up to 500 mA and restarted. No Change.

For now I didn't find any dislodged SMD.
As I can see there are no components between the CPU and the USB port.
The only two explanations I have:
1. CPU is defective, but still able to hold HOLD.
2. CPU is in a wrong state, keeping PWR_HOLD? up, but not yet offering USB.

I exclude a bad USB Port connection, because I resoldered it and also the consumption of 60 mA is too low.

vy 73 Peter DL4PJ

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