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QMX V4 will not mount

 

I just applied power, 7v, limited to 250ma. I long pressed the left rotor encoder.?
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When power jack is first inserted there is no current. After power is turned on, current is 40ma.
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The QMX does not mount as a drive in Ubuntu so I cannot install firmware.
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I am depressed. I had hoped to demonstrate this unit to Scouts in July.?
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What are my next steps?
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Thanks for your help.?
 

Correction, it draws 40ma before power switch is depressed.
 

On Sun, Mar 30, 2025 at 04:56 PM, Jim Brown wrote:
it draws 40ma
Hi Jim, wrong, 0 mA in this state and around 200 mA for a part of a second when firmware is running and for the whole time in firmware update mode.
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You may read QMX QMX_plus Startup to find more information about the start process and what to check for debugging.
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73 Ludwig
 

Ludwig,
I am glad to have this reference for later.
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As I read it, it assumes firmware is installed.?
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I cannot get my QMX to mount to my Ubuntu computer so that I can install the initial firmware.
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73, Jim
 

Jim, it seems that there is plenty of time before July for us to help you get this figured out.
Reading the reference Ludwig pointed you to is very useful.
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Something is probably shorting inside your unit.? There should be zero current draw when a power cable is connected, before pressing the 'on' button.? So the first thing is to find out why and remove that problem.
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The first thing I would do is to remove the bottom cover, and look very carefully for any metallic surfaces touching where the control/front panel and main cards come together.? The clearances are so small in the QMX that it is easy to have this type of problem.? A few typical issues are: the display mounting tab that needs to be bent over further, the soldered-in leads between the display and display mounting board, the sides of the encoders, and the back of the power connector.? If there are none of these mechanical shorting issues, there could be a simple soldering issue somewhere, like a little solder blob in the wrong place.? For this, I carefully examine the whole board with a good magnifying lens (bottom side first, since it is easy to see, and saw most of the soldering action).? Taking a well-lighted photo with your phone's camera and zooming in on it can also give a great magnified view.
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Let us know what you find, and we'll help you figure out the next steps.
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And if you're not up to debugging it yourself, Jeff W1NC will fix it for you and have it back to you in short order.
Stan KC7XE
 

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Many thanks for these suggestions Stan.
Jim

On Mar 31, 2025, at 4:46?PM, Stan Dye via groups.io <standye@...> wrote:

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Jim, it seems that there is plenty of time before July for us to help you get this figured out.
Reading the reference Ludwig pointed you to is very useful.
?
Something is probably shorting inside your unit.? There should be zero current draw when a power cable is connected, before pressing the 'on' button.? So the first thing is to find out why and remove that problem.
?
The first thing I would do is to remove the bottom cover, and look very carefully for any metallic surfaces touching where the control/front panel and main cards come together.? The clearances are so small in the QMX that it is easy to have this type of problem.? A few typical issues are: the display mounting tab that needs to be bent over further, the soldered-in leads between the display and display mounting board, the sides of the encoders, and the back of the power connector.? If there are none of these mechanical shorting issues, there could be a simple soldering issue somewhere, like a little solder blob in the wrong place.? For this, I carefully examine the whole board with a good magnifying lens (bottom side first, since it is easy to see, and saw most of the soldering action).? Taking a well-lighted photo with your phone's camera and zooming in on it can also give a great magnified view.
?
Let us know what you find, and we'll help you figure out the next steps.
?
And if you're not up to debugging it yourself, Jeff W1NC will fix it for you and have it back to you in short order.
Stan KC7XE

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