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QMX Screen Showing Nothing after Building and Loading Firmware

 

Hello,

Just finished building the QMX and loaded the firmware. The screen lights up, but there is no text. I have tried both reloading the firmware and adjusting the contrast using the capacitor, and neither solved the issue. Does anyone have any suggestions as to how to fix this, or what might be causing the issue?

Thanks,

Sepehr N6IRN
 

The cutoff leads can be hard to solder for the screen. Check them carefully.?
--
Colin - K6JTH?
 

I have checked the cutoff lids. There is continuity on both sides of every pin. Will check again just in case.

Thanks,

Sepehr N6IRN
 

It is the most common problem I see here. The grounds are easy to cold solder. After that, you have to trace voltage to the screen and ground.?
--
Colin - K6JTH?
 

Hi Sepehr,

Is there any change in the display if you adjust R305 trimmer pot on the display board?


Ed ?KN6NZW
 

Hi,

Yes, the brightness of the backlight changes.

Sepehr N6IRN
 

Just as a complement to my initial post and provide some more info:

  • The firmware loads successfully, as I was able to check the cat control menu and pull up the diagnostic page (screenshot below).
  • The screen lights up and backlight is present.
  • The backlight changes brightness the?R305 trimmer pot is changes.
  • Since assembly and setup, I have not seen any black boxes on the LCD, thus no sign of data being provided to the LCD
  • There is continuity between each side of the LDC pins that I soldered using the cutoffs.
  • The voltage between Vdd and Vss pins of the LCD is 2.57V.?

My assumption is that there is disconnection between the LCD and whatever feeds it data. I am still trying to figure out where it's supposed to be getting the data from and how to check continuity between the LCD pins and where they are supposed to be connected to. I would very much appreciate some expert help and inputs.

Screenshot of the diagnostics menu:



I am using a Duracell 9V battery. I obviously need to replace it, but I don't think that's the cause of the LCD issue since it was brand new when I initially plugged it

Thank you,

Sepehr Sahraian | N6IRN
President of Irvine Valley College ARC | N6IVC

Sent with secure email.

On Monday, June 3rd, 2024 at 8:12 PM, Sepehr - N6IRN via groups.io <n6irn@...> wrote:

Hello,

Just finished building the QMX and loaded the firmware. The screen lights up, but there is no text. I have tried both reloading the firmware and adjusting the contrast using the capacitor, and neither solved the issue. Does anyone have any suggestions as to how to fix this, or what might be causing the issue?

Thanks,

Sepehr N6IRN

 

Supply voltage is much too low (5.6 volts).? Get that up to at least 7 volts just to rule out low supply voltage as the cause even though the power supplies look OK. . A 9V alkaline battery just can't supply the current.? Then? see if your results change.
-Steve K1RF


------ Original Message ------
From "Sepehr - N6IRN via groups.io" <n6irn@...>
Date 6/4/2024 12:35:25 AM
Subject Re: [QRPLabs] QMX Screen Showing Nothing after Building and Loading Firmware

Just as a complement to my initial post and provide some more info:

  • The firmware loads successfully, as I was able to check the cat control menu and pull up the diagnostic page (screenshot below).
  • The screen lights up and backlight is present.
  • The backlight changes brightness the?R305 trimmer pot is changes.
  • Since assembly and setup, I have not seen any black boxes on the LCD, thus no sign of data being provided to the LCD
  • There is continuity between each side of the LDC pins that I soldered using the cutoffs.
  • The voltage between Vdd and Vss pins of the LCD is 2.57V.?

My assumption is that there is disconnection between the LCD and whatever feeds it data. I am still trying to figure out where it's supposed to be getting the data from and how to check continuity between the LCD pins and where they are supposed to be connected to. I would very much appreciate some expert help and inputs.

Screenshot of the diagnostics menu:



I am using a Duracell 9V battery. I obviously need to replace it, but I don't think that's the cause of the LCD issue since it was brand new when I initially plugged it

Thank you,

Sepehr Sahraian | N6IRN
President of Irvine Valley College ARC | N6IVC

Sent with secure email.

On Monday, June 3rd, 2024 at 8:12 PM, Sepehr - N6IRN via groups.io <n6irn@...> wrote:
Hello,

Just finished building the QMX and loaded the firmware. The screen lights up, but there is no text. I have tried both reloading the firmware and adjusting the contrast using the capacitor, and neither solved the issue. Does anyone have any suggestions as to how to fix this, or what might be causing the issue?

Thanks,

Sepehr N6IRN

 

Have you tried reflowing the solder on the 2x5 female header socket JP304 on the main beard as well as the male 2x5 header plug on the display board?


Ed ?KN6NZW
 

Sorry about that, had a brain fart, I meant JP206 on the main board and JP304 on the display board.

Ed ?KN6NZW
 

I inspected the QMX constructed by the OP of this thread. Soldering was of generally good quality. To be sure, I reflowed the solder on JP206 and JP207 on the main board and JP303 and 304 on the LCD board. System boots up and I can log into the terminal diagnostic, but the LCD does not display text. ?I did notice that some of the toroids wires might not have had their insulation sufficiently stripped prior to soldering, and those connections will need to be reworked later, but I do not think any of the toroids should affect the LCD character display, or the digital portions of the circuit.

From the Firmware manual, page 85-86:
--------------
After power-up, the system boots up on the linear 3.3V regulator (78M33). During the first half second, the system brings up the buck converters (3.3V and 5V power rails) and switches off the linear 3.3V regulator.?

IF there is a fault on any of this, QMX will not start; it will not start the receiver or transmitter, and will not power the LCD module or write anything to the LCD.
However, QMX will start the USB Virtual COM Serial port connection, even from the start when it is still powered via the 3.3V linear voltage regulator. When you connect a terminal emulator, QMX will display this diagnostics screen. You may be able to see from the displayed values (and colouring) where the fault lies.
-------------------

This leads me to think that there might be a problem with the power-on cycle. We took measurements of the voltage pins on both buck converters. It seems that the 5V and 3.3V rails are at their correct voltages, and the firmware diagnostics indicate both 12V and 3.3V are working correctly. However the 12V rail is showing the input voltage of approximately 8.9v. I tested all the other functions in the diagnostic screen, i.e. rotary encoders, paddles, etc. and everything is working correctly, only the LCD is not displaying characters. The LCD backlighting is on however, indicating that the LCD is being powered.

This particular QMX was built for 9V. So my question to the group is for a 9V QMX should the 12V rail actually be 9V? I could not find this information in any of the documentation, or in any of the schematics. As far as I can tell (and I am not very familiar with the QMX) is that the only difference in construction of the 9V and 12V variants is the winding of T501 in the transmitter and there are no other differences.?

73, Brian KM6ZX
 

On Tue, Jun 11, 2024 at 06:00 PM, Brian Moore wrote:
for a 9V QMX should the 12V rail actually be 9V?
Brian, "+12V" is only the label. The value is very close to the external supply voltage (see also here).

the only difference in construction of the 9V and 12V variants is the winding of T501 in the transmitter and there are no other differences.?
Yes

Could you show a screen shut of terminal - Diagnostics similar to a post before but with 9 V supply?

The backlight changes brightness the R305 trimmer pot is changes.
Also when using 9V as supply?

73, Ludwig
 

Could you show a screen shut of terminal - Diagnostics similar to a post before but with 9 V supply?
I no longer have the QMX in my possession and I forgot to get a screen capture during testing. We tested it at 9V with a reliable power supply. The diagnostics didn't show anything as failed or inoperative. I put a current meter in series with the radio and it was showing a current draw of approximately 100 mA after startup.

The backlight changes brightness the R305 trimmer pot is changes. Also when using 9V as supply?
The backlight is on, but it is not very bright as compared to the backlight on my QCX Mini. R305 does seem to have an effect on the brightness when using a reliable 9V power supply, however the effect is very small. I will recommend to the OP that he checks for shorts between the individual pins on the LCD. Maybe too much solder flowed and shorted something?

I loaned the OP my personal QCX Mini so he could at least have a working radio to get on the air with. I have never built a QMX, so am not terribly familiar with it. I returned the QMX to the OP since I don't really have time right now for further troubleshooting. He indicated he may send it off to someone for repairs. Overall I think the construction job was good and the radio should be repairable, once we know what the problem is.

73, Brian KM6ZX

?
 

Just a quick update regarding my issue with the LCD:

I ended up sending the rig to Jeff Moore, W1NC, for further inspection. He did an AMAZING job of troubleshooting and fixing the LCD data connection. There was a broken PCB trace which he substituted with a jumper wire. Not only did he resolve the LCD issue, but he also spotted and fixed a couple of other issues with the TX and SWR meter capabilities of the rig.

I have made several QSOs with the QMX and I cannot emphasize enough what a great piece of kit it is.

I would like to note that Jeff Moore provides this service at no cost, only charging for shipping and parts. Out of kindness and emphasizing the notion of "Hams helping Hams," he does not demand any money for the valuable time he puts in. Please, if you end up sending him a rig, consider donating, as he dedicates all donations to maintaining a reliable inventory of parts to continue this great service for the ham radio community.
 

Seconded.

73

-- Matt N3AR


On Thu, Jul 11, 2024 at 6:22?PM Sepehr - N6IRN via <n6irn=[email protected]> wrote:

Just a quick update regarding my issue with the LCD:

I ended up sending the rig to Jeff Moore, W1NC, for further inspection. He did an AMAZING job of troubleshooting and fixing the LCD data connection. There was a broken PCB trace which he substituted with a jumper wire. Not only did he resolve the LCD issue, but he also spotted and fixed a couple of other issues with the TX and SWR meter capabilities of the rig.

I have made several QSOs with the QMX and I cannot emphasize enough what a great piece of kit it is.

I would like to note that Jeff Moore provides this service at no cost, only charging for shipping and parts. Out of kindness and emphasizing the notion of "Hams helping Hams," he does not demand any money for the valuable time he puts in. Please, if you end up sending him a rig, consider donating, as he dedicates all donations to maintaining a reliable inventory of parts to continue this great service for the ham radio community.

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