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Lit Up but Blank Display

 

First of all, thank you for allowing me to join the group. I’m building a REV 1 QMX. On Sunday, I downloaded the 012 firmware. As I was downloading it, the backlight on the display lit up. The problem is that there is nothing there to display. I had the potentiometer turned all the way anti-clockwise. Nothing on the display changes as I turn it clockwise. Does anyone have a fix for this? If so, please be as detailed as possible. I’m admittedly somewhat technologically illiterate.

Thank you!!

73,

Bob - KD9RKG
 


Bob -

I think the first thing to do is to attempt to telnet into the QMX. This is described in chapter 8 of the operations manual. If you are able to establish a connection, then I think you're ahead of the game. At that point, I think the problem is probably just on the display board or the connectors that go to it. Check for bad joints or shorts on the connectors and components on that board.

If you can't, then the problem might be the SMPS boards. Again, check for open joints or bridges.?

I'm no expert at this, just have made enough mistakes of my own to start to know what to look for. Many other people in the group are far better at diagnostics than I am.

John, KI3J
 

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Thank you, John! I will give that a try and let you know how it goes.?

Bob - KD9RKG



On Dec 13, 2023, at 8:13?AM, john.christopher2 via groups.io <john.christopher2@...> wrote:

?
Bob -

I think the first thing to do is to attempt to telnet into the QMX. This is described in chapter 8 of the operations manual. If you are able to establish a connection, then I think you're ahead of the game. At that point, I think the problem is probably just on the display board or the connectors that go to it. Check for bad joints or shorts on the connectors and components on that board.

If you can't, then the problem might be the SMPS boards. Again, check for open joints or bridges.?

I'm no expert at this, just have made enough mistakes of my own to start to know what to look for. Many other people in the group are far better at diagnostics than I am.

John, KI3J

 

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John,

I check all my solder joints and they look good to me, although admittedly, I’m still a rookie. I removed the SMPS and checked all the joints and bridges. Can now see faint dark blocks across the top of the display, which tells me that the radio accepted the firmware. But turning the potentiometer clockwise clears the display. Also, the left control knob turns the QMX on but not off. I checked the joints on it and they look good. I’m hoping that these additional details will help you/someone point me a bit closer to a solution. Thank you!!

73,

Bob - KD9RKG




On Dec 13, 2023, at 8:17?AM, Bob Worden via groups.io <bob.worden65@...> wrote:

?Thank you, John! I will give that a try and let you know how it goes.?

Bob - KD9RKG



On Dec 13, 2023, at 8:13?AM, john.christopher2 via groups.io <john.christopher2@...> wrote:

?
Bob -

I think the first thing to do is to attempt to telnet into the QMX. This is described in chapter 8 of the operations manual. If you are able to establish a connection, then I think you're ahead of the game. At that point, I think the problem is probably just on the display board or the connectors that go to it. Check for bad joints or shorts on the connectors and components on that board.

If you can't, then the problem might be the SMPS boards. Again, check for open joints or bridges.?

I'm no expert at this, just have made enough mistakes of my own to start to know what to look for. Many other people in the group are far better at diagnostics than I am.

John, KI3J

 


Bob -

You hadn't indicated if you've been able to telnet into the QMX. I'm concerned because there might be a problem with the MCU (the processor chip) - that controls everything. It's encouraging that the QMX accepted the firmware, but the inability to do poweroff could indicate a problem. If you can telnet into it then there are some diagnostics that might help. Unfortunately I can't really think of where you can go from here. Measuring the 3.3v and 5v bus voltages would at least let you know if the system has the proper voltage levels, but I've read of instances where some builders have made mistakes when doing probing and done even more damage - and I don't konw exactly where to measure those on the board. I think you're going to need the help of someone who knows more about this than I do.


Sorry,
John KI3J
 

Possibly off the mark but I found the pot VERY sensitive.? First time I powered up I had the same issue but by turning the pot very slowly it all came up as it should but when I was turning it quick it went through the sweet spot and out the other side before the display could stabilise.
 


Bob -

Do you mean you could read the text when you say 'all came up as it should'? That would be very good news. It greatly reduces the possible things that could be wrong.

John KI3J
 

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Sorry, John, but no I could not read any text on the display. I can see very faint black boxes, but that’s it. I hope to get into it with Telnet this weekend. Thank you very much for your help.?

Bob - KD9RKG



On Dec 15, 2023, at 9:42?AM, john.christopher2 via groups.io <john.christopher2@...> wrote:

?
Bob -

Do you mean you could read the text when you say 'all came up as it should'? That would be very good news. It greatly reduces the possible things that could be wrong.

John KI3J

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