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Did anyone out there notice that FlexRadio is now copying QRP Labs? Not really, but their latest product (the Aurora series, announced right around Hamvention and scheduled to ship in 4Q25) is using EER?(aka polar modulation) generation of SSB. They worked with K1KP, the developer of the Polar Explorer that was demonstrated in 2019, to integrate the technology into a transceiver.

To be clear, I don't remember if the backlight actually did come on, as I didn't want to keep it connected to power any longer than I had to to check what the usb behaviour was (Up to that point the supply was set to act as a breaker as soon as an overcurrent event happened, vs supply limiting to a constant current which I did for the last tests). But the dark squares were very distinctive

Hi Stan

To #1, the DC plug isn't shorting, and the tab you mentioned isn't contacting the small transistor next to it

To #2, resistance of PWR_ON and PWR_HOLD to all other pins in that connector:
With PS #1 disconnected: PWR_ON to all >2Mohm, PWR_HOLD to all > 1Mohm, usually around 1.2M (I can get precise values to pairs if needed)
With PS #1 connected: The readings in this section aren't super stable, I think the meter I've got at home is suspect. Values are what they seem to settle to, initial readings are much lower
PWR_ON - PWM_5V : 50K
PWR_ON - Vin : 95K
PWR_ON - PWR_HOLD : 220K
PWR_ON - ADC_5V : 120K
PWR_ON - Vcc :? 130K
PWR_ON - +12V : 150K
PWR_ON - GND : 130K

PWR_HOLD - PWM_5V : 200K
PWR_HOLD - Vin : 310K
PWR_HOLD - ADC_5V : 105K
PWR_HOLD - Vcc : 100K
PWR_HOLD - +12V : 120K
PWR_HOLD - GND : 90K

To #3, I've created a facsimile out of a picture from the operating manual, imagine the blue squares are the colour of pixels on the display


I won't be able to do any power on tests for the weekend, as I don't have access to a current limiting supply at home, and I'm absolutely not plugging this into a battery until I've figured out what's up.

Thanks, Kait VA3KBY

On Fri, May 23, 2025 at 07:54 PM, Daniel Walter wrote:

I use a current and voltage limited supply when first testing kits

Current limiting can only do so much; a semiconductor can be destroyed WAY faster than a power supply can limit current; besides whatever energy is in the circuit or in the power supply's storage elements (capacitors) already, has already been provided and is available to assist in the damage.

Often the overcurrent event is a symptom of the failure, not the cause.? Semiconductors make excellent fast-blow fuses.

73, Don N2VGU

Functionally it will work fine for you to finish assembly and start testing.? Those capacitors affect only the bandpass filter and two low-pass filters.?

But check carefully first: things fit very tightly in QMX, and after installing toroids, etc, there will be very little working room to install the capacitors.? So look at some photos and get a feel for this to make sure you think you can fit them in before you move ahead.

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And note that it is very, very rare for one of Hans kits to be missing parts.? Those capacitors can hide in the recesses of the knobs, or alongside other parts.? So look very carefully again; you may have them.? I found one of my 33pF caps inside of one of the knobs, and another hiding in the bnc connector.

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Good luck,

Stan KC7XE

I had a 1% resistor sample kit whose resistors marked 10K were actually 1K.? I had some head scratching figuring out why the gains of my opamp circuits were all wrong.??

73, Don N2VGU

Here are a few questions, observations, checks to do, and resources for you to look at:

1) First a couple of checks based on your photos (the resolution got stripped, so it is hard to tell whether these are issues or not):

?? a) check the back end of your DC power plug.? It comes very close to other surfaces; make sure it is not shorting

?? b) on your PS board #1, verify that the big 'tab' on the lower large transistor is not contacting the drain lead of the other small transistor that is very close to it (ohm-meter check)

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2) Now a question to verify what I think you reported: you say that your main board + just the PS#1 board installed, as shown in your photo, draws current when attached to the power supply, with nothing else done on your part?? This should not be able to happen, and indicates a malfunction somewhere, since the power should require switching to turn it on.? Likely possibilities are

?? a) the PWR_ON line is grounded (or attached to some signal that is grounded),

?? b) the PWR_HOLD signal is somehow pulled high, rather than low per its pull-down resistor

?? c) some failed component on the power supply board.

The first two of these, a) and b), can happen via that 2x4 connector - these signals are adjacent to others in that connector that could cause the fault if shorted, either on the PS board, or main board.? You should be able to test with a multimeter during power-on the voltage on these two lines, and with power off the resistance between these lines and any others in the connector - they should have very high resistance to all other lines.

And don't raise the current limit above 250mA until this is fixed, to avoid possible damage somewhere.

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3) Another question for clarification: you said when fully assembled, the display turned on with a top line of black squares.? Did the display backlight come on? (hopefully not, this would be very mysterious).

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4) Resources:

?? a) please see this entry in the wiki regarding independent functional tests for the power supply boards [and test your 5V board #1]: /g/QRPLabs/wiki/37128

?? b) please see this entry in the wiki to understand details of what happens as QMX starts up: /g/QRPLabs/wiki/36878

?? c) please see this newer QMX troubleshooting guide in the wiki [still a work in progress, links to other wiki pages]: /g/QRPLabs/wiki/39617

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5) Another observation: since the QMX 'drive' appeared on your computer when you plugged it in, it indicates that PS board #2 (3.3V VDD) and your processor have at least basic functionality.? It may not hurt to load the firmware in this state.? You will likely have to manually power-cycle the QMX after it loads (rather than its usual auto-reboot),? but doing so will allow you to connect with the terminal and access all of the terminal diagnostics.? Those won't help with the above #2 issue, but will allow you to check many other things.

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I hope this helps.

Stan KC7XE

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I believe the excess wire is quite intentional, due to Hans' correct assumption that some will make mistakes and need a little more. Knowing I'd already wasted a foot or two of wire, I pre-cut lengths a bit shorter than the recommended length, so I wasn't throwing away a few inches away with each core. It all worked out perfectly in the end and the radio worked flawlessly with no fixes required. Actually, all four of my QRP-Labs builds have worked flawlessly, which I attribute more to Hans' excellent instructions more than my own ability.

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Jack, thanks for the Kits & Parts link, that's going in my bookmarks. I'll look for your QST article but unfortunately the ARRL decided to not honor their subscription terms so I did not receive that issue.

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Many thanks Stan for this infos. I will now tests with my qmx+ and fldigi.

Currently, when operating CW with fldigi and QMX+, if you set the fldigi CW modem set for CAT keying, fldigi uses the CAT 'KY' command to send the characters - it does not try to use PTT to turn the carrier off and on for dit and dah.? This seems to work fine with QMX, but there is a bit of a trick to it: you need to set the fldigi CAT keying to use 'Elecraft', not 'Kenwood'.? [Note that you leave flrig radio set for QMX, only the CAT keying to Elecraft.] ? For some reason the 'Kenwood' setting fills each KY command with one character followed by many spaces; this fills the QMX buffer with spaces and does not work correctly.? But the Elecraft setting sends one character per KY command, and works for me.?? It would be nicer if fldigi sent several characters per KY command, and just let QMX keyer do the timing.

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I have not done extensive testing with this, but it seems preferable to having QMX assert carrier with each TX, and is already in the firmware.

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Stan KC7XE

I received my kit for a high-band QMX this Tuesday, and have been working off and on over the course of the week to assemble it. I've gotten to the point where it's fully assembled, and after several close inspections under magnifying glass and microscope, I can't find any significant defects that would lead to the problems I've been seeing, outlined below

I'm powering the QMX from a 10V, 250mA current limiting DC power supply. The core issue is that the board (That I have never programmed) is drawing far more current than the assembly document suggests it should at this stage)
The different cases I've run:

Main board connected to power, no additional boards attached: 0mA drawn
Main board connected to power, PS #2 board attached, all others detached: 0mA drawn
Main board connected to power, PS #1 board attached, all others detached: Initially current limited to ~8-9V @ 250mA. After an inrush period, stabilizes to 10V @ ~100mA
Fully assembled QMX: Current limited to ~6V @ 250mA. LCD screen turns on with solid black squares displayed. Appears as a usb device immediately upon plugging in to a computer, without pressing the potentiometer button.

I've been focusing my troubleshooting efforts on the interaction points between the main board and PS #1, and haven't found any obvious shorts. Checking the pin header connection to PS #1 with the board attached, I didn't see any shorts to ground. I also double checked and ensured that there weren't shorts around the power amp transistors, and around X201 where I saw VCC being used.

I've attached photos of the back side of the main board, and front side of PS #1 as installed under a magnifying glass below. If any other pictures are required let me know and I can provide.
Note that there is some debris near the PA transistors in the second photo. I cleaned that and tried again, and the board still enters the current limited condition.

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Thanks and 73 de VA3KBY

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I received my 20m-10m QMX kit and am currently assembling it. Unfortunately, the kit I received was missing the three 33pF and the 100pF capacitors (C401, C404, C521, C516). It will probably take a while until I receive the missing parts and I wonder if it is still possible to finish the build and start testing the device (basic tests like: will it turn on etc). Or should I just let it sit and wait?

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73,?Dennis DM4NTZ?

Audio levels problem solved ! It was due to incorrect parameters in the AGC settings. I swear I did not do it....think these defaults came with v1.02 ? The AGC threshold was set to 15...should be 8. Also sample blocks was 2....should be 5. The audio levels on all modes are now roughly the same. Audio attenuation setting I have now increased to -100dB, seems I have very sensitive headphones.

de VK6XT?

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On Thu, May 22, 2025 at 10:03 PM, Curt wb8yyy wrote:

Whether the via is needed depends upon which or both have connections.?

Drilling is not an acceptable rework method for boards with plated-thru holes.? This is a 6-layer board with internal layers you should never go any where near it with a drill bit lest you ruin the board.

73, Don N2VGU

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On Thu, May 22, 2025 at 09:44 PM, Stan Dye wrote:

That's why I recommend to carefully scrape or burn/sand off the enamel before soldering the coil wires, which avoids much of this issue.

I think that the assembly instructions should recommend this approach, I think folks are poorly-served by encouraging use of the burn-and-pray method, it just fails too often.??

Perhaps it works OK for the QRP Labs elves, who do it all of the time and learn the technique, but we keep hearing the same cries of woe about open transformer connections ad infinitum.

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Hans, please change the instructions!

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73, Don N2VGU

Hans explains it so well, I almost understand it.?

I'd like a solder pot, but it will have to wait until I have a bigger workspace and that day may not come. My bench is so cramped that I think a pot of melted lead would be a rather dangerous thing to have on it! As is, I'm always tripping on cables or catching wires with my sleeve. So I scrape, sand and tin.

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While waiting for my QMX+ kit to arrive, I bought a small crochet hook but my first attempt at using it was a disaster and since my wire supply was limited, I wound with the normal method. I still screwed another toroid up, but caught the mistake before soldering it in...I still ended up with about 13" of spare wire when finished. Which is still sitting on top of my washing machine and no doubt driving my wife crazy.?

On Thu, May 22, 2025 at 09:35 PM, Jerry Gaffke wrote:

Could be process variation between different manufacturing lines for the BS170?

Could be variations in cap and inductor impedances for the LPF?

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Probably more likely different load impedances and/or latent failures due to electrostatic discharge or poorly-regulated or excessive supply voltages.

73, Don N2VGU