After a factory reset my QMX+ runs fine for hours running wspr. If I attempt to change parameters through the front panel...turn on clock...dot delim etc it will lose audio connectivity to wsjt and through headphones. Factory reset and reboot wsjt does restore things back to normal. Perhaps I should not try to customise anything whilst under control of WSJT?

Thank you Stan! I did as you said and now I have Terminal and my PTT is enebled!

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BR/Sergey

UB3AZK

I have exactly the same problem after updating the software, the radio stopped receiving, I can hear noise.

My radio generated an SWR alarm after WSJT-x briefly transmitted on one of the "receive only" bands during band hopping. Whilst this is a very desirable traits, I discovered that it was no longer possible to QSY via CAT. Power off reset cleared the condition.

de VK6XT.

I am having the same problems

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de VK6XT?

Yes, they are also a slightly different shape.? And made with a completely different manufacturing process and material, a ferrite blend, rather than the powdered iron typically used in the other cores.

When you turned it off and back on, did you do it with the switch on your power supply, or with the QMX front button?

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Your symptoms are that you now have an internal power fault, which prevents the QMX+ from powering on.

One possibility:? If the input voltage from your power supply ever exceeded 14V, for more than a second or two, even with the QMX+ turned off, or if there was a high voltage transient from the power supply, it may have fused the input protection TVS diode (D110).? 13.8V on continuously for a period of time possibly could also damage that diode, which starts conducting somewhere between 13V and 14V.? There are of course other possibilities, only measurements will tell.

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It will be best to turn down your voltage to about 7V and set a 250mA current limit while diagnosing this, if possible, to avoid any new faults.

Stan KC7XE

On Thu, Mar 27, 2025 at 08:14 PM, Stan Dye wrote:

440mA and 340mA are way too high, indicating something pulling down on the 3.3V power supply.

Oops, I wrote too quickly again.? In your case it could also be something else.? A voltage very near your 7V input should be appearing at VI of IC101, rather than the 5V that you see.?? Check carefully the 12V input as it appears on the 3.3V SMPS.? Has it dropped to 5V at that point (being pulled down somewhere in the interconnect)?? Or is it dropping from 7V to 5V across Q102?? That measurement can give you a hint, if you don't find the error doing the independent SMPS tests.? I suspect (based on your measurement of LIN_REG_EN) that you will see it dropped to 5V at the input of Q102, which would mean that the 12V bus is not getting cleanly to your 3.3V SMPS via the connectors.

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Good luck, Stan.

I was just building a microphone for the qmx and then I plugged it into my power supply to test it. I on purpose to turn the voltage down from 13.8 and then turn it on. It worked fine but I needed to turn it off and back on again for it to connect to my computer. I turned it off and then when I tried to turn it back on it was a high-pitched noise for about half a second in the screen backlight turned on and then it turned off and now shows no signs of Life except power draw when I press the button.

Sorry for my previous message (now deleted).?? Ludwig's value was correct, as always.

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After removing the SMPS cards to test them, as Ludwig has recommended, also measure the resistance between Vcc and GND, and Vdd and GND on the main board, which should be a few k-ohms each.? And also measure Vcc to Vdd, and 12V to Vcc and Vdd - each of these should have a very high resistance, in the mega-ohm range.? You likely have a short or a failed component somewhere - and the first place to check is the voltage rails, because if that is where the short is, it can continue to cause additional failures.

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For all further testing, until after a successful power-on is completed, please set a current? limit on your supply to about 250mA if possible.? Without a current limit, some types of issues can fuse your SMPS protection diodes or damage a main board component.? I hope your new 3.3V SMPS is still ok.? 440mA and 340mA are way too high, indicating something pulling down on the 3.3V power supply.

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Stan KC7XE

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I'm very glad you got it working!

I'm very sad it failed again.

When pushing the card into the bottom enclosure, we almost always 'torque' the front panel a bit.? This could cause the connectors to seat differently, or a cold solder joint to open up.? So it may be worth a few tries of repositioning the front panel onto its connectors (if you haven't done that already) to see if the problem will go away.

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And if you are in the USA and send it to Jeff W1NC, you will get it back and fully operational much faster and cheaper than ordering a pre-built kit.

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Stan KC7XE

On Thu, Mar 27, 2025 at 08:34 AM, Mehmet Dinch wrote:

The plot doesnt look any better..

Try several different settings of either 'Frequency min.' and/or 'Frequency center'.? I was able to (with a few trials) get the plot to complete out to the full x-axis range.? I think that a 'complete table' is the issue for distorted audio, rather than the shape of the plot.? A couple of my band plots have very strange variations like that, but do not noticeably distort the audio since I got the plot to complete all the way across.

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See the more verbose message I just sent about this issue here: /g/QRPLabs/message/141884

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Stan KC7XE

On Thu, Mar 27, 2025 at 05:19 PM, Ellis Simon GM4GZW wrote:

The phase calibration sweep for 20M also looks odd and is different to the others which are all nice curves

Based on some experimentation with some similar phase calibration results on a couple of bands on two of my QMX, it appears to me that when the phase distortion curve is started, but not completed, then the audio gets distorted.? And the lower the value it stops at, the worse the distortion.? In your example, the curve of values only goes to about a value of 600 on the horizontal DAC axis.? So my theory is that whenever your voice waveform has an amplitude that results in any DAC value of over 600, there is not a proper result stored in the calibration table for those values, and 'bad stuff happens', resulting in distorted audio.

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So (if my theory is correct, and it seems to have worked on my 2 QMX), if you can get the calibration to put in measured phase values across the whole range of the DAC (about 2600 for 12V builds and 2000 for 9V builds), then the resulting voice quality is good, even if the graph looks uneven or strange.

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I was able to get my calibration to finish on the 'bad' bands by adjusting (as others have noted) the "Frequency min" and/or "Frequency center" in the band configuration screen.? For some reason these do affect the way the phase calibration runs.? I had to play with different values in one or both of those settings, but without too much trouble got all of the bands to have "complete" phase distortion curves.? The 'curves' were not always pretty, but I don't think that's so much the issue as having data initialized for the full range of DAC values? that will be used (based on the input voltage and drive level, both of which Hans pointed out need to be set before calibrating).

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After I changed the band config settings for calibration, I restored the band settings to their original values so the other diagnostic sweeps would still function in the same way, and so my default 'center frequency' would be what I want on each band.? [These settings don't affect normal transmit/receive operation, we just needed to 'seed' them differently to get completion of the calibration table.]

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I hope this is helpful to someone, and maybe someone can corroborate my theory on getting rid of the distorted audio....

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Stan KC7XE

Ellis

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Distortion on one band only could be RF getting into audio. See if same thing happens when transmitting into dummy load. And maybe an external signal report.?

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Curt

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Thanks everyone. I had done everything correctly but in my excitement to try out the rig, not fitted the link in JP501. Obviously skimmed over page 36 as well !

Jeremy,

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I would test both power boards offline following QMX QMX_Plus Power supply test Process from the QRP Labs Wiki.

IC101 VI should be at least 5.3 V + 0.6 V (elevated GND of IC101). Your 5.0 V is not enough for 3.3 V output.

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Without a running controller LIN_REG_EN is made by a voltage devider, 0.5 * "+12V".? Your 5.1 V is wrong. Please consult schematics page 1 to see where to check.

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73 Ludwig

Hi,

I installed the 1_01_003 beta firmware yesterday and I am amazed at how it has transformed my QMX+ (rev 2 board).

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I am, however, perplexed at the fact that the SSB audio is distorted (on another receiver) only on 20M. This only occurred after calibration and the audio becomes absolutely clear again after disabling the phase predistortion. All other bands have good audio with and without predistortion, and the RF output is within normal limits on all bands, although 20M is a little lower than others at about 3W. I am using a 12V stabilised PSU and a good dummy load, via a Bird isolator, giving me a solid signal into my receiver.

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Trying to think of an explanation made me consider that the LPF used for 20M (LPF 3) may not present a good load to the PA, so I looked at the LPF sweep using PuTTY. Here is the sweep for 20M:

The 14MHz line is in a less than ideal part of the curve, whereas the bands which share this LPF are better placed. Is this significant?

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The phase calibration sweep for 20M also looks odd and is different to the others which are all nice curves (except 160M which sounds fine!):

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This is the 20M USB IMD sync optimisation curve, the title of which has been overwritten by the asterisks of the curve.

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The 20M USB curve looks identical:

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Here is the adjacent band 30M curve for comparison:

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Everything on the board looks good and the radio otherwise works perfectly. I am perplexed at why only one band is distorted (it really is unreadable) yet 160m, which has similar calibration curves but a great looking LPF, Sounds OK.

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Any ideas?

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The simple answer is to switch off predistortion, but that doesn't solve the problem!

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73

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Ellis

GM4GZW

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On Fri, Mar 28, 2025 at 12:44 AM, Mehmet Dinch wrote:

Thanks for sharing your settings.

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Are these setting post calibration?

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