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QMX+ Initial Power Up Display Shows Only Boxes
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Upon very first power up of QMX+ at 7V , there was no smoke, but the display only showed boxes.? Adjusting the display trimmer only made the boxes disappear.?
Thanks.
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73, Don K0DBL |
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Don,
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Perform these steps in order, let us know where things go off the rails.
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How many milliamps is the rig pulling from your power supply?
It will be about 200 ma at startup, somewhat less once the switching power supplies are working.
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Check the voltage across D109 (should be 3.3v)
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Is signal LIN_REG_EN low?? It starts out high at power up when the QMX uses the 78M33 linear regulator,
once the processor gets the 3.3v SMPS working then LIN_REG_EN goes low.
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Is the voltage across D108 5.0v?? If so then the 5.0v SMPS is probably working too.
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Can you talk to the USB port on the QMX using putty as described in the Operations Manual
to see debug information?? Can use a web browser on many different kinds of computers for this.
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Jerry, KE7ER?
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Hi Don,
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I don't see mention of the PCB Rev you have, but if you are slow to start building (like me) and have a Rev 1, then you might need to load the firmware.?
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I spent three days reading these forums and testing this rail, that voltage, the other ohm's, etc. etc etc.? It was a very deep rabbit hole for sure.? Anyway I finally realized that taking my time and testing every connection while I was building led to a terrific build - no issues - except I was missing the firmware.?? Once I loaded that everything tested perfect - just as Hans said it would in the manual.? So if you are Rev 1, try to load the firmware.?
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Rev1 - Step 2.30 - Item 3. Note that the QMX+ is normally supplied without firmware and you must install firmware first, before anything will happen (see subsequent section after finishing this “final checks” section).
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I hope this helps you - if not maybe it will help someone else that was slow to start building their Rev 1.
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Cheers and 72
Gregg / N6ZUE
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Thanks for the replies gentlemen. ?Your suggestions have been very helpful, but I'm not out of the woods yet. ?My apologies for not getting right on this, but my wife decided that Valentine's Day was more important than troubleshooting my QMX+!
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Gregg: my version is Rev 2 (I should have included that from the beginning). Just to be safe, although the firmware file was the same, I still replaced it with the file I downloaded from the website.
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Jerry: the voltages across D108 & D109 are good. ?I don't know how to determine LIN_REG_EN. ?I finally figured out how to connect PUTTY on Windows and could get into the Terminal Applications. ?Everything there seems to look good (it looks like I'll have to do some adjustments for ADC I/Q eventually).
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Ludwig: I checked the connections between the display/main board connections. ?This might be the problem for the display. ?I found two pairs of pins on the display board, not on the main board, that show continuity. ?
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The first pair: As you are looking at the front of the display board, the pins with continuity are between the two shaft buttons, the second (counting left to right) "vertical pair". ?I'm not an expert, but looking at the trace diagram, it doesn't appear that these should have continuity. ?I see no solder bridges. ?
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The second pair: As you are looking at the front of the display board, pins 2 and 6 have continuity. ?Looking at the trace diagram, these pins are connected to the first pair. ?
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Should these pins have continuity? I don't see where I could have made a mistake on this board.
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Thanks in advance!
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73, Don K0DBL |
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On Sat, Feb 15, 2025 at 07:48 PM, Don K0DBL wrote:
Should these pins have continuity?Don, absolutely not. Pin 2 is VCC (5 V) and pin 6 is connected to an I/O port of the controller. This port is used as an output. 5 V at ports of the STM32 is dangerous. Don't switch on the QMX until the problem is solved. I hope, this I/O port survived.
Hard to tell remote.
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73 Ludwig
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Possibilities I can think of:
1) a solder flake/bridge under the plastic connector pin retainer, on the back side of the control board, which you can't see - let's hope it's not this, because it would be a pain to fix, and it's quite unlikely
2) the circuit card traces connecting the lower pins to the upper pins - one of them passes directly between the two pins as shown with the red line in the photo clip below.? If a bit of the solder-resist (green) coating was scratched off at the left side of that trace, it could easily solder-bridge to that top pin.
3) a fault in the display module that connects the two signals.? Cutting or removing one of the two connector leads between the display and the board would allow finding which 'side' of the interface has the short.? Maybe cutting one, then soldering it back together wouldn't be too hard...
None of these is a "likely" fault, and any one of them is a pain to find and fix.? So whatever it is, good luck in finding it.
Stan KC7XE
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You may want to consider sending the QMX+ to Jeff W1NC.? He likely will have it fixed and returned to you in very short order.? And you can't beat his service.? See this post of his with info: /g/QRPLabs/message/137552
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Hi Don,
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I just finished my build of the QMX+. I have completed two other successful QMX builds.
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So, today I applied power as suggested and wound up with the square box display. I figured it was the interface between the display board and the main board. I got the iron hot and reflowed as many joints as I could. After eliminating 99% of the possible I went back to the inside top header. So looking straight on from the front, over the top edge, start counting from the left to the right and pin #5 is the one. After I got the solder to flow from the pin to the pad?? --->? new QMX+ is on the air.
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Hope that helps.
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73, Dean/ N2TNN |
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