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QMXP QMX+ device suddenly shut down and dont turn on #QMXp #QMXplus

 

Do not apply over 12.0 volts to the QMX+, that's what you should do.
You blew the the SMBJ13A protection diode at D110, a big rectangular surface mount thing near the power connector.
Shown in the lower left corner of the first page of the schematics.
It starts conducting when it sees around 15 Volts.
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If you remove it from the board, the rig will probably start working again.
But you won't have over-voltage protection, and must be very careful not to exceed 12.0 Volts.
I recommend you order a replacement, Mouser has it, part number 652-SMBJ13A.
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Jerry, KE7ER
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On Fri, May 30, 2025 at 06:44 AM, Melih wrote:

QMX+ device suddenly shut down while doing ft-8 and
I checked it with a multimeter from the dc power input,
there is a short circuit and the device does not turn on.
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There is a short circuit in the marked areas in the picture. Does anyone know what I should do?
 

My assumption is that you blew D110, but there are several other possible ways for input power to be shorted.
Jerry, KE7ER
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On Fri, May 30, 2025 at 07:10 AM, Jerry Gaffke wrote:

Do not apply over 12.0 volts to the QMX+, that's what you should do.
You blew the the SMBJ13A protection diode at D110, a big rectangular surface mount thing near the power connector.
Shown in the lower left corner of the first page of the schematics.
It starts conducting when it sees around 15 Volts.
 

i am used voltage is 12.2 volt but tomorrow and today worked total 6 hours
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What are the other reasons?
 

I don't understand, does the QMX+ now work?
If this is an intermittent short, you might find it by pushing on parts and flexing the board when it is powered up.
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If the 12v supply is still shorted as in your previous post, there's probably a part on the board that is getting hot.
Feel around carefully with your fingers to find any hot spots.
Once such possible reason for a short is D110, and if so it will be getting hot.
Current should be limited to a maybe 1 or 2 Amps, perhaps by using a fairly weak power supply that can't give much more.
The power supply could be less than 12v (perhaps 5v) when doing this test.
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Jerry, KE7ER

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On Fri, May 30, 2025 at 07:44 AM, Melih wrote:

i am used voltage is 12.2 volt but tomorrow and today worked total 6 hours
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Sorry, I checked the wrong place. There is no short circuit in the input. In this case, why does the device not work? I tried different voltages with low amperage (5, 11.8, 12.2 volts) but the device does not turn on.
 

When pressing the power button, there is sound coming from the speaker.
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You wrote:? "why does the device not work? ...? device does not turn on."
By device, I assume you mean that the QMX+ does not turn on.
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If so, read the section "QMX Switch on power" on this webpage for an explanation of how the QMX/QMX+ powers on:
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Jerry, KE7ER
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On Fri, May 30, 2025 at 09:54 AM, Melih wrote:

Sorry, I checked the wrong place. There is no short circuit in the input. In this case, why does the device not work? I tried different voltages with low amperage (5, 11.8, 12.2 volts) but the device does not turn on.
 

QMX+ was working, I was doing ft-8 but it suddenly shut down, now it is not opening, there is no short circuit
 

On Fri, May 30, 2025 at 10:57 AM, Melih wrote:
QMX+ was working, I was doing ft-8 but it suddenly shut down, now it is not opening, there is no short circuit
Melih, did you get your QMX+ working?
I understand you verified there is no short at the power input connector.
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From your description, including the sound in the speaker when you push the button, one of the following two things have happened to your QMX+:
1) One or more of the PA transistors (BS170) shorted, which is shorting down your 12V supply internally so the QMX+ can't start up.
2) One of your power supply protection diodes failed, causing an internal power supply short that prevents your QMX from starting up.
I don't know why such a failure happened, but perhaps after finding it we will be able to figure it out.
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Look at the Wiki for information on debugging this, and ask further questions about that process here and we will try to help.
You will need a good multimeter and be able to read the schematics to search for the failed part(s).? First thing to check is probably the 4 BS170 PA transistors.? See if any of them are shorted source-to-drain.
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I hope this is helpful,
Stan KC7XE
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