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On Thu, May 15, 2025 at 08:59 AM, PHILIP GRAITCER wrote:

what exactly does a trigger cable do?

Please use Google or your favorite search engine or ai assistant with "describe PD trigger cable functionality" for details.?

It has a tiny chip molded into the connector which negotiates the desired voltage using the USB-C PD protocol.? The power bank itself has the multi-voltage regulator.

On Thu, May 15, 2025 at 09:16 AM, Chris wrote:

the S appears on the display. But then the SWR Tune no longer works. It only works again after an OFF/ON

You can also clear the 'S' by entering and exiting the menu system, no power cycle required?

Ok. ?I will check that this evening. ?But even when the signal level was at -33dbm there is no gain from the input to the output of ic405 or ic406, ?in fact I believe there was nothing at all on the output of ic405 or ic406 from what I remember with the signal level at -33dbm. ?

Heinz, the antenna is a 20m long EFHW and, as is well known, can be used on 7 and 14 MHz. The resonance circuit (Fuchs circuit) transforms from 50 ohms to an impedance of approximately 3k ohms.

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I've tested all of this successfully, of course. It also works in CW mode.

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Only in SSB does the QMX software seem to react unexpectedly due I guess interference (e.g., in the microphone cable). This leads to the S in the display indicating too high SWR and to the Tune SWR mode no longer functioning correctly.

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I'll investigate this further.

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73 Chris

Hello Ron,

if you see two files in firmware upgrade mode (jumper set) the QMX starts for the first steps. Firmware 1_00_027 is loaded already.

When jumper is removed the QMX should start when pressing the volume encoder. But if you see nothing at the display and no backlight maybe the start procedure isn't completed. Please tell us for normal start the supply current when volume encoder is depressed and for a few seconds after released. And which voltage do you use?

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73 Ludwig

But VDD isn't at the pin header to sub-PCB #1. Or did you check also for PCB #2?

Check voltage at the pin PWR_ON (sub-PCB #1). There should be a voltage near the input voltage when volume encoder isn't pressed but 0 V if depressed.

And at first, remove all subboards and check for the mainbord resistance from VDD to GND, VCC to GND, "+12V" to GND.

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73 Ludwig

I have not been able to see on the initial first power up any means of loading firmware on my QMX+ radio. I was able to see some evidence of 2 files on E drive which is the USB drive on my computer by shorting AUX2 to ground before power on. The two files in E drive are? file 1_00_027.QMX and EEPROM. EEPROM is an empty file.. Have I missed something here or do I have a bigger problem that cannot be solved easily??

Any help would be greatly appreciated. Thank you, Ron W6ZQ?

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I can confirm that voltage does make it to plug in PCB #1. I did notice that VDD has continuity to ground when checking for shorts on the pin header. Nothing visible was identified

Or a processor pin bent? under and only intermittent contact.

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--

Allison
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Post online only,?
direct email will go to a bit bucket.

On Thu, May 15, 2025 at 05:32 AM, Bruce Akhurst wrote:

?IIRC the DROK thing needs 1.5V minimum headroom of input voltage over output.

DROK and others make buck-boost units which will increase OR reduce the voltage input to output.

I use this fixed-voltage one with my 4S LiFePO pack which can go as high as 14+V fully charged, or really any battery within its range. ?

I use this adjustable unit for general purpose use, battery charging, etc. and to regulate my 20V Dewalt batteries: ?

I use one of these high-voltage buck converters (intended for golf cart use)? to tap my 56V lawnmower/leaf blower batteries for 12V power: ?

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73, Don N2VGU

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On Thu, May 15, 2025 at 08:30 PM, ZeusK8CES wrote:

There’s no current flowing at all

Realy not when pressing the volume encoder?

In this case please trace the voltage from the socket to plug-in PCB #1. Via the Wiki document you will find a sketch of the contacts to the SMPS boards.

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73 Ludwig

On Thu, May 15, 2025 at 04:47 AM, Bruce Akhurst wrote:

getting a 18V 5A lithium tool battery and an old fashioned analogue (fixed or adjustable) regulator to 9,12 or 13.6 V is simple and noise free. ?

And, in the case of 9V, will waste half of the battery power as heat, 12V wastes 1/3, etc.? OK in some cases, probably not OK if you are carrying the battery to a mountaintop.

73, Don N2VGU

By the way thanks. I’ll follow this document and see if I can’t get the processor to load firmware?

Figure I'd update this with a conclusion:

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The reset procedure sent by Ron worked perfectly but did not resolve the issue. Screen would appear to work normally about half the time and then would error out after a few button presses or would error out immediately after booting up the radio. All voltages and tests seemed to be coming back as expected and from everything I could see the radio itself was functioning just the screen was failing. Ron offered to take a look at the radio since I had hit the limits of my electrical troubleshooting skills so I shipped it off to him for inspection.

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He found the exact same issue as me, testing seemed to show no issue but the screen kept failing. VFO was confirmed as working and tuning, button presses, processor, oscillator were all functioning with no faults, the screen signal isf getting dropped somewhere between the processor and actual LCD. He tried replacing the processor, screen, and control board combinations which still did not resolve the issue and allowed further testing to confirm signals and voltages were all correct. I think the only thing we didn't test between the two of us was the actual binary signals getting sent to the screen but that should have shown up in one of the other tests or replacement items that Ron tried.

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So seems like I got a faulty board or failed in a very unique way during assembly. Ron was super generous and offered to send me a spare QCX he had on the shelf which I now have set up and running which I'm super excited about. Will take a while for me to be fluent enough at morse code to send signals to you all but hopefully will be able to connect with everyone in the near future.?

Same issue here with mine.? Both QMX and QMX +.? ?I believe all setup is in order. Power out is only about 2 watts or so on 20m and 40m. No one responds to me. Put me in the puzzled column.?

There’s no current flowing at all from what I can tell. ?Amperage supply never changes ?

One more question. Please tell us the supply current before pressing the volume encoder, while pressing and after release.

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73 Ludwig

On Thu, May 15, 2025 at 07:28 AM, Ryan Wesolowski wrote:

Like Stan wrote before, it looks like IC405 and IC406 are in overdrive state but not broken. It would be the first time reading about broken ones or find this when repairing a QMX(+).

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Please check these voltages using your DMM:

For Q508 in RX mode the voltages are at S 0 V, at G around 3 V and at D near 0 V.

IC402 pin 9 should be around 2.5 V and depending on the active BPF one of the pins 10, 11, 12 and 13 should be the same.

IC403 pin 7 and 9 should be around 2.5 V. Pin 2 and 14 should be around 1.6 V. Using your oscilloscope you should see there (2 and 14) the LO signal with low at 0 V and high at 3.3 V (or so).

To repair QMX(+) I had to replace Q508, IC402 and IC403 already.

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Could you show please screen shots from Terminal - Hardware tests - RF filter sweep and Test ADC I/Q for a lower band and a higher band?

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73 Ludwig

That’s another part of my issue. My pc doesn’t seem to recognize the QMX being connected. So I’m having difficulty loading that in. I checked and reflowed the solder points on the USB C port on the board with no avail?

Hello,

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please read this document from the QRP Labs Wiki to see which signal should be at which value at which time when starting a QMX.

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73 Ludwig