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Hello, I've just finished building my QMX+ and when I go into the diagnostic screen, I noticed that the "Right btn:" Is indicating "Press" at all times. When I press any of the other buttons it moves up to another button press. I began to troubleshoot this a bit and I started by removing the display from the rest of the QMX+. Then the press goes away. From there I tested the buttons one by one. They are functioning correctly. When I test the resistance in the circuit, I noted that I see 3.3kohms, 6.8kohms, and 13kohms... which seems to line up with what I'd expected based on the schematic.?

Can anyone offer any more troubleshooting advice? Thank you.

Brandon?

I would check carefully your soldering on / near pin 6 of the JP302 connector and its companion on the mother board.? Maybe there is a short to another node, or a 'cold' solder joint with resistance.

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As you have noted, the three buttons (excluding the power button) all use one electrical line with different resistances.? On the processor side of the connector, there is a 2.2k pull-up resistor to Vdd.? So when you press a button, it gives a voltage divider between 2.2k and the resistor value of the button.? The processor detects the divider voltage on its input pin with an internal A/D.? When no button is pressed, the processor sees the full-scale voltage.? The left button has the lowest resistance, so gives the lowest voltage to the processor, about 2/3 scale.? The right button gives a higher voltage, at about 3/4 scale .? And the right-encoder button gives a higher voltage still, about 7/8 scale.

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Since your processor is seeing a constant right-button when none are pressed, there is somehow getting a 6-8k resistance in the connectors/trace to the processor.? Pressing any button will put another resistance in parallel with that, causing a different voltage level, therefore a different button detection to the processor.

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Good luck finding the problem.? Shouldn't be too hard.

Stan KC7XE

Thanks, Stan. I got a nice thick tip and reflowed all of the connections on the display, and the header pins for the display. Powered it up and there was ZERO phantom button pushing going on. I used it for several minutes like this, ran the GPS diagnostic screen, went through several menus, configured a bunch of stuff... it worked PERFECTLY! Slid the bottom of the case back on and powered it up and I see the issue again. I've looked VERY closely to make sure nothing is shorting on the case. Even after removing the board from the case it still happens again. I'll probably just hang this one on the shelf and order an assembled kit. Thanks.?

Brandon

I'm very glad you got it working!

I'm very sad it failed again.

When pushing the card into the bottom enclosure, we almost always 'torque' the front panel a bit.? This could cause the connectors to seat differently, or a cold solder joint to open up.? So it may be worth a few tries of repositioning the front panel onto its connectors (if you haven't done that already) to see if the problem will go away.

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And if you are in the USA and send it to Jeff W1NC, you will get it back and fully operational much faster and cheaper than ordering a pre-built kit.

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Stan KC7XE

Thanks for that recommendation! I just might do that. I reached out to my local club and there is someone here with a working qmx kit that is willing to let me take measurements and troubleshoot.?

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One thing that I cannot make heads or tails of... today I powered on the board, loaded up diagnostic info... things are fine. So I let it run for a bit and the a phantom press several minutes later. Then a different button a few minutes after that. Pictures included.?

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If button status changes while it is just sitting there, it suggests a temperature-related bug.? Such a thing can happen with a 'cold' solder joint, or bad connection through a connector.? I would try gently moving the front panel (such that it changes the pressure on the connectors to the main board), and see if the button status changes.

Stan, thank you for sticking with me on this. I'd reflowed 7 of the 11 pins and the last 4 were apparently where the problem was. I was reading the schematic incorrectly perhaps, because I thought I had reflowed all the pins that had to do with those buttons, but apparently I was mistaken. Anyhow, the QMX+ is working fantastic now for over an hour. Appreciate you and all you do.

Brandon

p.s. Hopefully I'll catch ya on the air with this soon!?

Check that the tab on the display is bent over and not shorting the capacitor on the PCB. ?I went round and round on this symptom until I found it. ?You will have to carefully remove the display from the pcb to correct it.

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?I’ve seen this 3 times now. ? It’s an easy thing to overlook.

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73
Jeff Moore
W1NC

Jeff, I appreciate that. I did look at that and wonder! I went back and checked the build guide because I knew it was in the instructions for the QMX. I avoided trying to remove that display at all cost. Thankfully I do not think that was the case here. I do see that the alignment is flexible enough that it certainly can be an issue. I'll get in touch with you about making my QMX work if I cannot figure it out soon. As it is now, I think my QMX+ will be my primary radio. I've been on the air and it TX's on all but a few high bands. Low power, but I'll see if I can get it improved.?