On Thu, Apr 3, 2025 at 01:25 AM, <ng433@...> wrote:
Any ideas where to start looking for the short?
Check all the elements connected to the VDD rail and all the places where the VDD rail goes. With some luck you will find a tiny solder whisker or a tiny part cut from an element during construction and shorting VDD now.
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VDD to GND is like .5 ohms
and
Lin_Reg_EN signal is stuck at .7 volts?
may point to a broken controller.
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73 Ludwig
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Re: QMX+ rev 3 freezes shortly after boot
On Thu, Apr 3, 2025 at 10:25 AM, Stan Dye wrote:
Maybe Ludwig has more ideas.
Not so much in the moment. Maybe I will do a test using a cheap evalboard containing a STM 32. I want to check what will happen in case of VDD = 4.5 V or so. Will it stop? Yes, if not it's no proof for the particular QMX+. But if it stops it would point to raising VDD first and stopping the STM32 after this and not vice verse.
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It is not likely a capacitor issue; their failure rate is very low. ?It is more likely a temperature issue, where something is thermally expanding just enough to cause a short, or a component is failing and shorting as it heats up, or a 'cold' solder joint is changing its connectivity.
This is also my favorite.
There is also a lower possibility for an unreliable solder joint for one or more IC pins.
And there is a lower possibility for failure inside an IC. Lets assume the TXCO or IC202 is stopping when heat a bit up. This would stop the controller and the SMPS couldn't work right.
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It would be nice to use an oscilloscope to check the clock signal before and after IC202 in "frozen" state.
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It maybe interesting to see what happens when TCXO and IC202 are cooled a bit or heat up a bit during work. Would the period until the controller stops be significant longer / shorter?
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73 Ludwig
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Re: Available Hand Mics for QMX SSB ?
Eric,
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I do not see an order page for the mic.
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Dean
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Re: Help with partially fried QMX
Stan - that was super helpful.? Thank you for taking the time to type that out for me/other hams that want to learn by doing (or by destroying).?
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After i read the earlier post about the pin to T507 i assembled enough non-panicky energy to actually go and look at the traces in the assembly manual.? Lo, what did I see?? Indeed a direct connection to T507.? I was operating at 7V for a 9V QMX, but indeed over extended period.
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The support of you, Steve, and others who have answered my questions over the years since my first QCX build gives us electronically-uneducated persons the readiness to venture forth and enjoy this world of home-finished qrp radios.
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It is all very appreciated. Thank you!
JD
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Re: QMX+ rev 3 freezes shortly after boot
On Thu, Apr 3, 2025 at 02:25 AM, Stan Dye wrote:
A question regarding this statement.? Did it freeze up before you cut the power??
And I'm confused about your jump from 0.8A to 0.2A.? You mean it was running at 0.8A nominally, then dropped to 0.2A when it froze up?? This seems wrong
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Hi Stan, apologies - you’re right. I mistyped when I said it jumped from 0.8A to 0.2A. The jump was from 0.08A to 0.2A, and it did freeze before I cut power.
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I’ll do another sweep of the boards for small shorts or solder blobs or cold solder joints as well. Thanks for your help!
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Re: QMX and power bank PD
The USB cable is a good option to be able to use any pd power bank and not need to make a custom battery with buck converters and other kit electronics.? Also one less thing in a bag.?
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Mine runs a little over 12v, 12.3 was the max it hit, so I would expect yours to perform around that.
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The variable pd cable is also viable, just change the voltage without the radio connected as it might change to the higher, 15v, option and that is no good.
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73
Jason
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Re: QMX and power bank PD
Did a search looking for this kind of assurance. I have a factory built QMX - I've not been able to use it yet - which I was able to power on using those cheap AA battery banks filled with Duracell batteries to make up the 12v.
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It's a nice little power solution, if a bit of an expensive way to go about it, even if you populate the power bank with rechargable AA batteries. So it was from there I went looking in to a power bank solution.
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Yesterday I purchased an Anker power bank and a 12v USB to DC PD cable (links below). Hopefully these should do the job safely and reliably. I also purchased one of those cheap little voltage testers just to see what power is going through to the QMX from the power bank. I'm not expecting anything super accurate, but hopefully a ballpark visual would be good (linked to it below).
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Voltage tester:
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Power Bank:
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USB Cable:
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Paul,?
Take heart! Most of the things I teach to younger (and some almost at my age, 80) I learned by mistakes, misunderstandings, and just trying this and trying that. Just the fact that you admitted how you had made the mistake shows you will be a good teacher. ?Good teachers can’t be proud because if you are proud you can’t confess your mistakes. ?Keep learning, keep on keeping on, and see one, screw up one, then teach one…. We are all brothers in this hobby.
My favorite simile of a good hobby is one that gives you a heart warming feeling, similar to John Wesleys “heart warming feeling” at Watersgate. ?Italian changes you and your response to the world. In this messed up world we need a hobby to help us cope and stay sane. ?Ham radio has done that for me for 65 years. ?
toggle quoted message
Show quoted text
On Apr 3, 2025, at 2:15?AM, Paul G8MAD via groups.io <paultostevin@...> wrote:
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Hi,
?
Although I got my licence over 40 years ago, I never pursued amateur radio as an interest until now. So, I was very excited this week to take delivery of my first HF rig - a new assembled QMX+. Even more excited, when connecting it to a homebrew efhw I could hear CW and see the decoded morse code (which I am currently learning).
?
But all that excitement was marred by me being an idiot and not inserting the cr2032 battery for the RTC correctly. I assumed I just had to push it into the holder when I should have slid it in under the +ve connectors - so when the time was being lost on shutting down the rig I found that I had bent the +ve positive pins so they were in contact with the -ve terminal of the battery. I bent them back so when inserting the battery correctly they are now in contact with the +ve side of the battery but I lose the time every time I power down.?
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I have tried different configurations with the Real time clock parameter set to QMX+ RTC or software, manually setting the time or attaching the antenna for the internal GPS module and letting that set the time but with no success. So have I damaged the RTC components?
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Paul
G8MAD
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PS it was reading the posts in this group and all the support that it offers that made me decide to go for a QRP Labs radio. Thanks.
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Re: Available Hand Mics for QMX SSB ?
Karl, I cut the cable and soldered each wire to two other 3-wire cables. Each individual wire was insulated with tiny heat shrink tubing, and finally the entire cable at that place was insulated with two layers of heat shrink tubing.
The wires are thin and you need a steady hand, but it's doable.
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Zrinko Ivan, 9A7AM
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Re: Available Hand Mics for QMX SSB ?
That is very interesting - never thought of using a 50 Ohm speaker. How did you attach the two plugs? My experience with Baofeng mikes is that the wires are very flimsy.?
--
Karl Heinz - K5KHK
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Re: SSB audio distortion #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
Hi Stan,
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Out of curiosity, does it complete on consecutive runs for the same band or is just, seemingly, random?
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After some couple of hours of messing around with band settings, I did get it do a complete run on 20m. Without changing anything else, I ran it again to be consistent, the calibration quit at about 600 with another, seemingly, random plot!
I couldn't get it to do a complete run again after that with the same band settings.
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Mel. M0KMD.
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Re: SSB audio distortion #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
Oops.? My reply and comments were intended for Mehmet.?
I have some bands that have crazy-looking graphs like the ones he posted - even after I got them to complete all the way across.? But after they completed all the way across, the gross distortion was gone.
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Your note, Yun, about the 80m plot not finishing all the way across, but still you get good audio (after turning off the swap) - that shows that my theory is not the complete story, even though it has worked for me and a few others...
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Re: QMX+ rev 3 freezes shortly after boot
All the resistance measurements look fine, as do the numbers on your diagnostic screen capture - showing that the power supplies are working fine, without any issues, at least when you took that screenshot.
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Since it seemed to change behavior after you cleaned up around connections, and disconnected/reconnected the front panel, I was hopeful that you dislodged whatever small solder whisker that may have been shorting.? Sometimes they can be unnoticed.
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On Wed, Apr 2, 2025 at 08:06 PM, Michael Shiplet wrote:
Unfortunately, it froze again shortly after that. I believe I'd entered into the RF Filter Sweep menu item and was watching the output when I saw the current jump from 0.8A to 0.20A and cut the power.
A question regarding this statement.? Did it freeze up before you cut the power??
And I'm confused about your jump from 0.8A to 0.2A.? You mean it was running at 0.8A nominally, then dropped to 0.2A when it froze up?? This seems wrong, so please clarify the currents you measure while power is on and it is running 'normally', before it locks up, and any changes in current you saw.
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The nominal running current in receive mode, and during most hardware tests should be about 120mA at 12V (0.12A), with GPS installed.? During LPF sweep and SWR sweep, it will briefly go up to about 0.6A, then come back down.? Only during Tx (T key in diagnostic screen) should it go up to almost 1A.??? In your last statements, I think you say the nominal current draw when working correctly is 200mA, then it goes down to 140mA when it freezes.? This is interesting, because at 12V, 200mA receive current is a bit high, and the 140mA is close to normal.?? [Unless my two QMX+ are not normal.]
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I would carefully inspect your front panel board and your main board, everywhere top and bottom, under high magnification.? You may find a little something (solder blob or whisker, or bit of cut-off wire) that is causing the problem.? It is not likely a capacitor issue; their failure rate is very low.? It is more likely a temperature issue, where something is thermally expanding just enough to cause a short, or a component is failing and shorting as it heats up, or a 'cold' solder joint is changing its connectivity.
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Maybe Ludwig has more ideas.
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Re: QMX/QMX+ architecture
On Fri, 2025-03-21 at 16:42:35 +0000, Alan G4ZFQ via groups.io wrote: Presuming the QMX is like the QDX, in IQ mode there is no 12KHz offset.
The QDX manual has a good circuit description. Alain, Thanks for your response. I found the description of the receiver in CW mode in section 5.22 "AGC system" of the QMX operation manual (1.00_026/27). There it is described how the receiver signal passes through 25 steps of processing. From this description, also verified by tests, I conclude that the VFO is set to the dialed frequency with an offset of 12 kHz plus the side tone offset (nominally 700 Hz), assuming the the USB output during CW mode with IQ enabled is the unprocessed 24-bit output from the ADC. Maybe this description should be placed in a separate section, since it is not only of interest to the understanding the AGC system. I guess that a similar description will be needed for the new SSB mode, describing both Rx and Tx functions. Since I come from a different background (Automatic Control), I have some difficulties understanding the rationale behind all the steps in the receiver path. Why is the side tone frequency added already at the Tayloe Mixer/QSD mixer? An alternative would be to run the CW filter in zero-beat mode in the I/Q domain and mix the sidetone in front of the DAC. Zero beat is not a problem since there are no low-frequency noise nor bias after the 12-kHz mixing. A dual low-pass filter will then be needed, but the order of each filter would be about half of a corresponding bandpass filter. Also, the Hilbert transform (used for phase-shifting) can be removed and the Goertzel filter becomes a trivial moving average. A zero-beat indicator could be added to the display. The bandwidth of the low-pass filter is also easy to parametrize using Tustin transformations. If needed an offset of the center frequency can be added. The subsampling/decimation and interpolation steps can also be absorbed in the low-pass filter chain by implementing filter blocks with different sampling rates. 73 Anders SM5KAE
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Re: SWR and PWR does not show lcd
I've tried the "TUNE SWR" in "Hardware Test" and it works perfectly.
If I transmit, PWR and SWr indications don't appear on the top right side of the LCD display.
I have the "Display " option enabled in the setup.
THX
73's Miguel EC7ZV
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Martin,
I figured my QMX+ translates best, if the keyer speed is set to the approx. speed of the incoming signals. Be it received or when in practice mode. The manual hints at some parameters to play with for the decoder. My settings are the defaults.
Norbert, DA2CW
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I think it is unlikely that you could harm any circuitry by shorting the Vbat terminals together.
You could have drained your battery, if it was in for any length of time, since the + terminal could have shorted the battery + and - together.
So first thing is to try a new battery, inserted correctly.
And do you have your GPS set for Vbat power or Vdd?? If it is set for Vbat, and Vbat is drained, it won't keep time when off.? When you use the GPS for the clock, based on earlier messages in this forum, I understand you need to set RTC control to 'software' (due to a bug or 'feature' of the current firmware), in order for the GPS to continually update the clock.? [And note that the GPS may take a long time to get clock sync when you first turn it on in a new location - at least many minutes.? Subsequent sync times will be much faster.]
Stan KC7XE
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Re: Help with partially fried QMX
On Wed, Apr 2, 2025 at 08:29 PM, VA2OJD wrote:
Is there a single spot, somewhere on this forum, where it lists key measurements to check when troubleshooting?
Have you looked at this forum's wiki?? There is a topic specifically for the BS170s.? It has some helpful diagnostic guidance.? And you can search messages in this forum for BS170 and find a good number of entries, with different people being guided in their diagnostic efforts.
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Since your QMX was working for a good amount of time, a good possibility is that you fried your BS170s - most likely just them and not the driver and Q507.? This can occur, especially if you are running FT8 at more than 12.0V (for a 12V build) or 9.0V (for a 9V build).? Or if your QMX puts out more than 5W on a band at the correct voltage.? And especially if you combine over-voltage with some higher SWR on your antenna (probably more than 2:1), which can happen intermittently on wire antennas if the wind is blowing.? Doing any of the above over an extended time has risk of gradually beating your BS170s into failure.? That's why Hans has in big red print in his manuals to a) not run above 12V and b) not run above 5W.? And this is especially true with constant carrier modes like FT8, which add heat in the finals to the mix.? CW is more forgiving, because it is lower duty cycle.? At 5W the BS170s are pretty much up to their rated max, so going above any of the parameters puts more stress on them.? [This is true of their use in (tr)uSDX and other QRP radios, too.]
Stan KC7XE
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Hi,
?
Although I got my licence over 40 years ago, I never pursued amateur radio as an interest until now. So, I was very excited this week to take delivery of my first HF rig - a new assembled QMX+. Even more excited, when connecting it to a homebrew efhw I could hear CW and see the decoded morse code (which I am currently learning).
?
But all that excitement was marred by me being an idiot and not inserting the cr2032 battery for the RTC correctly. I assumed I just had to push it into the holder when I should have slid it in under the +ve connectors - so when the time was being lost on shutting down the rig I found that I had bent the +ve positive pins so they were in contact with the -ve terminal of the battery. I bent them back so when inserting the battery correctly they are now in contact with the +ve side of the battery but I lose the time every time I power down.?
?
I have tried different configurations with the Real time clock parameter set to QMX+ RTC or software, manually setting the time or attaching the antenna for the internal GPS module and letting that set the time but with no success. So have I damaged the RTC components?
?
Paul
G8MAD
?
PS it was reading the posts in this group and all the support that it offers that made me decide to go for a QRP Labs radio. Thanks.
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Re: Help with partially fried QMX
On Wed, Apr 2, 2025 at 08:29 PM, VA2OJD wrote:
the middle, radiating contact of the BNC is connected to ground via T507??
Yes, of course.? In most radios with an internal SWR meter.? But this is DC ground.? RF flies through the transformer almost untouched.
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Michael Shiplet
Jason
David Wilcox K8WPE