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Re: QMX+ high pitch noise on power. Now dead.
Where is D110 on the qmx board? I can try to check its state. On Fri, Mar 28, 2025, 6:17?AM Nico Smith via <nicosmith873=[email protected]> wrote:
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Re: QMX+ high pitch noise on power. Now dead.
I turned it off with the QMX power switch. Earlier today it was exposed to more voltage for a short period of time but it was still working fine after that. I'm not very good at reading schematics but what measurements should I do? On Thu, Mar 27, 2025, 11:44?PM Stan Dye via <standye=[email protected]> wrote:
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Hi Stan,
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Thanks for the tip.
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I did have a go at messing around with the band config for 20m but I was trying to get a plot similar to the examples rather than aiming to get a complete run.
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Could you share your band config please as a guide. I know that mine will be different..
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Cheers,
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Mel. M0KMD. |
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QMX won’t power up
Hello. I was using my QMX on 40m and 20m FT8 with a known good antenna and computer connection, successful QSOs, and no SWR lock outs or other signs of issue.?
The QMX screen went to all backlight with no LCD characters displayed for 1-2 sec and then went to a mix of full block LCD and some apparently random characters. Screen has no obvious physical damage. I was not transmitting at the time.?
I attempted basic battery / power troubleshooting to no avail. With a known good power source, it will not power on. Confirmed it is not limited to a screen issue, there is no RX as tested with audio output.?
What other troubleshooting is recommended? I’m ok with basic electrical repair, but don’t see myself doing and surface mount repairs. And I’m hoping there’s a possible test to rule out failed components and possibly an easy fix.?
I have explored the archives and didn’t see a similar problem noted. Thanks for any help.? |
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QMX+ loses audio.
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? |
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Re: Toroids: Do I have these sorted correctly?
#QMXplus
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. |
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Re: QMX+ high pitch noise on power. Now dead.
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 |
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Re: QMX not powering on, IC101 voltage too low
#troubleshooting
#power
#problem
#qmx
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. ?
Good luck, Stan. |
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QMX+ high pitch noise on power. Now dead.
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. |
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Re: QMX+ SSB audio distorted on one band only
开云体育
Stan,
This seems to have worked for me. Thank you! It took some time playing with the limit/center values to fix 17,15,12, and 10 meters. 160 and 11 are still broken but I don't use either of them.?
Tony
AD0VC
From: [email protected] <[email protected]> on behalf of Stan Dye via groups.io <standye@...>
Sent: Thursday, March 27, 2025 8:32 PM To: [email protected] <[email protected]> Subject: Re: [QRPLabs] QMX+ SSB audio distorted on one band only ?
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 curvesBased 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. ?
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
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Bruce Akhurst
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