Re: SWR and PWR does not show lcd
OK I guess it's a mystery then.?
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Re: Startup issues with QCX Mini (Rev. 3)
Thanks, Ron. I’ll definitely start there. Tnx & 73, Rich
Hi Rich, since this is a new build I think the best first thing to do is verify good solid connections especially between the control board and main board and between the display board and main board. This male pins need plenty of heat as they are fairly large. The socket leads aren’t quite as heat absorbing. Since you mention both control issues and display issues that is definitely the best place to start. Good luck. 73….Ron Hi all,
I've just finished building a QCX Mini (Rev 3; software version 1.09a; 30-meter version). When I powered it up for the first time, I got the intro screen followed by a 160-meter frequency. Having read the advice to do a factory reset if I didn't get a band select screen, I attempted to do that, and that's when my problems began. First, going to option 7 (other) and then heading for option 17, I found that the menu options stopped at around 9. Then, once I tried to move past that point, the display either went blank (still fully lit but no info) or started producing gibberish. After cycling the power several times (and waiting 30 seconds or longer before powering up again) trying to "get lucky," the display now goes to gibberish after option 4 or 5 on the main menu. Any thoughts on what the issue might be and/or how to try to resolve it? Many thanks in advance.
73,
Rich, W2VU
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On Tue, Apr 8, 2025 at 05:57 PM, Bill Jobes wrote:
I'm suggesting a WIKI on troubleshooting how-to procedures and techniques, not being told to take an action while presuming all readers know how to do it.?
Yes, this would be very nice.
Unfortunately, I don't know who would offer their spare time to provide good write-ups of how-to procedures for all of these.
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But the nice thing is, if there is a wiki recommendation that you don't know how to do, just ask here - and someone will likely jump in and help - there are tons of examples of this behavior in the message archives.? And then with a little effort from someone, the procedure could be added to the wiki.
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Stan KC7XE
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On Tue, Apr 8, 2025 at 02:34 PM, Bill Jobes wrote:
It's a shame there is not (yet) a resource here for we non-EE PhD's to access for guidance on how exactly to check and resolve at least the common problems that these otherwise fine radios manifest.
Ludwig and others have already documented troubleshooting approaches for the most common problems in this forum's wiki.? The fluctuating power/bias current is not a common problem with a known solution that can be easily documented.
Also, keep in mind that everyone on this list is a volunteer.? I haven't added to the wiki, because I just haven't taken the extra time to do so - it does take time and effort to make a good wiki posting.? You are welcome to help by consolidating responses (like the one I just provided to Andy, and other responses to posts about the same problem) and add them to a new wiki entry for fluctuating bias current.
And there are a LOT of them.? Both kit and factory built rigs, based on postings here, are a crapshoot when power is first applied.
That is very much an exaggeration, Bill.? Keep in mind that Hans has sold many thousands of QMX/QMX+ radios.? And only a small percentage of people assembling them have reported issues - yes, when reading this list it seems like everyone has issues, but only those who do are posting them here - without counting, I venture to say far less than 10% (a generously high estimate) of all QMX/QMX+ kit builders report problems.? And some of the most common of those problems were avoided with recent versions of the hardware - so the numbers of problems have significantly decreased.
A new WIKI where the forum experts could contribute precise tips and tricks to diagnose and fix problems would sure be appreciated.?
I agree with Ludwig.? The WIKI is already here, and already has ideas for many of the most-common problems.
What I think we need is more help in making more good entries to that wiki, derived from successes recorded in the many forum posts, and perhaps a better overall roadmap pointing to the appropriate entries for different categories of problems.
?
One reason QMX/QMX+ are as inexpensive as they are, is because they are user-supported.? If Hans had to take the time to write a good troubleshooting guide for all of the problems we find solutions for, he would have to charge twice as much for the radios.?? His current documentation and assembly guides are excellent, far above what some other vendors provide for much more expensive radio kits.
Stan KC7XE
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I will do that once the radio is back in hand.
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Ludwig you ask "Why not the current WIKI?"?
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Mostly because there are often suggestions to do this, do that, check this and check that, without offering specific advise on exactly HOW to execute the suggestions.
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I'm suggesting a WIKI on troubleshooting how-to procedures and techniques, not being told to take an action while presuming all readers know how to do it.?
?
?
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Factory built 12 volts, works perfectly. I've only made a few hundred CW QSOs. -27 firmware installed. With case $165 plus postage from Japan. JS6TMW
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On Tue, Apr 8, 2025 at 02:34 PM, Bill Jobes wrote:
the radio is now enroute to Jeff Moore, whom I am positive will cure it.
Please let us know what he finds.? This is a very tricky problem, with many possible causes.
Stan KC7XE
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On Tue, Apr 8, 2025 at 02:11 PM, WB9YXA wrote:
The Duty cycle on the Bias SMPS always shows 0%, even as the current jumps around in the red.
This is a bit different than some others have reported, where their bias smps is maxed out.
This suggests that the processor may be sensing a higher-than-needed current, and trying to reduce it.
Maybe this suggests a problem with the bias control circuit (Q501, Q502, Q516 and surrounding components), or some other signal shorted to the tx_bias line.
This really is a tricky problem.
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On Tue, Apr 8, 2025 at 02:11 PM, WB9YXA wrote:
What bothers me is that the output power seems to jump around wildly.? If I go to the diagnostics screen and key the transmitter, the Bias SMPS shows fluctuations in current that correspond to the fluctuations in the output power.?
There could be many causes for this.? Some are assembly-related, some are board smd soldering issues, and it could also be a failed component or bad port on the processor.
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Here are some of the assembly-related things to check for bias current issues, via inspection and your multimeter:
- Make sure L504 and L514 (two of the through-hole inductors you put in) are properly soldered, and not cracked.? This type of inductor is a bit fragile, and it is easy to break them with a little too much force.
- Make sure your diodes are all installed the correct direction.
- Make sure L501 (the small 330uH coil) has not been broken from the board during assembly.
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Some board SMD soldering issues to check that affect bias current:
- make sure C504, the large tantalum SMD capacitor, is properly soldered on both ends.? Also test that it is not shorted internally.? Jeff W1NC said he has found C504 soldering issues and failure in some boards he has repaired.
- verify the soldering of Q501, Q502, and Q516.? One user found that Q516 was poorly soldered.? You need to check these under good magnification.
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Hopefully one of those will hold the solution to your? particular problem.
Good luck, Stan KC7XE
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The combination of all the sweeps you sent show the problem and lead to the solution.
And the rev1 board connectivity is all in place properly, or the sweeps would look way different.
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First a bit of design background:
Ideally, a bandpass filter will have the frequency of interest centered in the band.? But in the QMX design, some bandpass filters are shared, so this can't fully happen.? For the mid-band QMX, 20m and 17m share a bandpass filter.? So you center the filter between those bands, usually with each band just off the edge of the filter. ? And 15m has its own bandpass filter - BUT it shares a toroid with the 20m/17m filter, so all three bands interact - the 15m turns are used for the 20m/17m filter.
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Now, from your filter sweeps:
15m (21MHz) filter:? the center of the filter is low, closer to 18MHz, leaving 21MHz with about 18dB of attenuation.? So that filter needs moved up to get 21MHz in its passband.? Moving it up requires less inductance in the toroid (fewer turns, or turns spread out).
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20m/17m (14MHz/18MHz) filter:? the center of this filter is also low, <13MHz.?? And 18MHz has about 18dB of attenuation.? It needs adjusted upward in frequency so 14MHz is at one side of the passband, or a bit outside the passband if necessary, so that 18MHz is also close to or within the passband, each with just a few dB of attenuation.
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Thankfully both need adjusted in the same direction.? If you have the windings all bunched together, perhaps spreading them out evenly will reduce the inductance enough.? But I suspect you will need to remove a turn from the 15 turn part - this will reduce inductance in both filters sharing the toroid.? So try removing first one turn, then checking the scans, then if they are still too low, remove another turn, which may move the filters too high - but if so you can compensate by squeezing the turns together to increase the inductance again.
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So why did this happen on your build?? There is up to a 20% tolerance in the toroid manufacture, and you may have gotten one that was out that far.? But I suspect another reason: The rev1 style of routing the signal through the IC402 between inductor and capacitor will add a small amount of capacitance to the filter, and this needs counter-acted by reducing the inductance.? The number of windings on the inductors for the mid-band version (which came out later than rev2) were tuned for the way IC402 is used on the later boards, with less capacitance.?? This would affect mostly the higher frequency bands, due to the smaller capacitances needed in those filters.
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One additional adjustment to consider:
The LPF scans look good, but the LPF for 15m has 21MHz at or just above the cutoff frequency - which will attenuate 15m a bit, before it even gets to the BPF.? It's not too bad as-is, but you could try and spread out the windings on L510, to move the LPF cutoff frequency up a bit.? If the windings are already fully spread, you could remove one winding, and then squeeze the remaining windings together to keep 21MHz near the cutoff edge. ? Spreading the windings of L513 may also help a bit - but don't get too dramatic here, unless you have means to test the harmonic rejection of the LPFs.
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I hope this is helpful - making the BPF adjustments should improve your receive on 17m and 15m by almost 18dB, which is 3 full S-units.
Good luck, Stan
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QMX+ T507 winding direction?
In the QMX+ does the polarity of the 10-turn windings on T507 (part of the Fwd/Ref power detector) matter? In the assembly manual the photo looks like they're wound to be mirror images of each other. I wound mine so the turns advance clockwise on both sides.
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Will this cause a problem with RF power measurement? Or worse yet, cause a serious impedance mismatch for the lowpass filters and finals?
?
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On Tue, Apr 8, 2025 at 11:34 PM, Bill Jobes wrote:
A new WIKI
But why not the current Wiki?
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Re: QMX+ with ~1000 tone on 12M & 6M
Hi, all -
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Where does this issue stand?
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I find that in my recently completed QMX+ (Rev. 2 1_00_27) I am now hearing that 750Hz tone
(when comparing a 750Hz tone at ).
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I happened to tune up to 10 meters today and the band is now not usable, since the tone is
so loud.?? I can't believe that the tone was there when I first completed the rig, about 2 weeks
ago ... I don't think I've been up on 10 meters since then.? Now, I notice the tone on the lower
bands as well, but much weaker.
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I was about to try a system reset to test if it is some setting that I did that is causing the tone,
but I noted one post in this thread said a reset didn't help.
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Has there been a resolution of this?
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Thanks -
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Bruce K1FFX
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Re: Startup issues with QCX Mini (Rev. 3)
Hi Rich, since this is a new build I think the best first thing to do is verify good solid connections especially between the control board and main board and between the display board and main board. This male pins need plenty of heat as they are fairly large. The socket leads aren’t quite as heat absorbing. Since you mention both control issues and display issues that is definitely the best place to start. Good luck. 73….Ron
Hi all,
I've just finished building a QCX Mini (Rev 3; software version 1.09a; 30-meter version). When I powered it up for the first time, I got the intro screen followed by a 160-meter frequency. Having read the advice to do a factory reset if I didn't get a band select screen, I attempted to do that, and that's when my problems began. First, going to option 7 (other) and then heading for option 17, I found that the menu options stopped at around 9. Then, once I tried to move past that point, the display either went blank (still fully lit but no info) or started producing gibberish. After cycling the power several times (and waiting 30 seconds or longer before powering up again) trying to "get lucky," the display now goes to gibberish after option 4 or 5 on the main menu. Any thoughts on what the issue might be and/or how to try to resolve it? Many thanks in advance.
73,
Rich, W2VU
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Thank you all for your input and support.? I have a rev 4 QMX (not QMX+).??
?I did a lot of work this morning resoldering every joint before identifying the failed 3.3v power supply component.? I didn't see a bridge, but that doesn't mean one wasn't there.??
I did check all the resistance measurements recommended to id a short, and all had excellent resistance.? ?9.3k ohms was the value of Vdd to ground, every other measurement was higher (ranged from 25K to 1.5M).? At this point I don't believe a bridge still
exists.??
I feel more comfortable, attempting a startup with another 3.3 v power supply bd.
Again, THANK YOU.
Regards,
Wilson (NT5AT)
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Show quoted text
One question: which version of kit did you have?? v1, v2, v3, v4?
There are several different possibilities for a burned Q109.
All of them come from a short on Vdd or one of its control lines (LIN_REG_EN, PWM_3V3).
These shorts could come from solder bridges, or a tiny flake of solder that migrated somewhere, or from mechanical issues: the tolerances are very close when assembling, and metal surfaces can easily touch together.? So in addition to inspecting soldering,
also look very closely at the assembled unit (without bottom cover), and see if anything from the various assemblies is touching.? Typical issues are the LCD mounting tab that needed bent over, the 10 pins connecting the display to the mount board, the encoder
bodies, and the back side of the power connector - maybe others.? Also the soldering of the connectors to the SMPS: the connector 'pins' are a bit longer than the pads (if not trimmed), and can touch or create solder bridges to other SMPS components on the
top side.
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After inspection, first thing to do is measure resistance to ground on each of Vin, +12V, VDD, and VCC, on the main board, without the SMPS installed.? And then the resistance between each of these voltage rails.? The resistance to ground should be at
least a few k-ohms.? There should also be at least a few k-ohms isolation between each of them.? Also measure the resistance on the control pins to both 3.3V and 5V SMPS (PWR_ON, PWR_HOLD, PWM_5V, LIN_REG_EN, PWM_3V3).? They should have no continuity to any
other pin on the connector, and have a high resistance to ground and Vdd and +12V.
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Hopefully those inspections and measurements will show something that could have caused the over-current that burned Q109.?
Good luck, Stan
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On Tue, Apr 8, 2025 at 11:59 AM, James wrote:
This is a little off topic but the charges to deliver my natural gas is almost twice what my actual gas bill is each month.
At least your is broken out so that you can see the cost breakdown.? Before deregulation and the ability to choose gas providers, it was a single lump sum per therm, so there was no insight into the distribution, gas, and facilities cost.
73, Don N2VGU
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Re: QMX+ bias current + output power fluctuating
So it was nice of Hans to send you a new board.? Did it include all the components, or did you have to remove them all from the faulty board and transfer them to the new board?
Either way, am I correct in presuming you had to build the radio all over again?
I'm curious as one of mine with the exact same symptoms is now on the way to a forum guru for repair.? Thus increasing by no small sum, my cost for the radio.
Bill W3WJ
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Re: SWR and PWR does not show lcd
Mine is switched ON and it doesn't seem to display either power or SWR. Factory assembled unit.?
It seems like there are a lot of subjects missing from the operating manual. Is the actual operating manual the combination of the assembly and operating manuals? Anyone know? Thank you.?
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Andy, the QMX+ I recently completed shows Exactly the same symptoms as you describe in your second paragraph.
I checked all components that I installed and re-soldered literally every point on the pcb. No change. The radio seems OK in all other respects. Other than wildly fluctuating bias current and output power.?
Since I too lack the knowledge to complete a troubleshooting of the bias system, the radio is now enroute to Jeff Moore, whom I am positive will cure it.
It's a shame there is not (yet) a resource here for we non-EE PhD's to access for guidance on how exactly to check and resolve at least the common problems that these otherwise fine radios manifest. And there are a LOT of them.? Both kit and factory built rigs, based on postings here, are a crapshoot when power is first applied.
A new WIKI where the forum experts could contribute precise tips and tricks to diagnose and fix problems would sure be appreciated.?
Good luck with yours.? I'll be following the discussion with interest.
Bill? W3WJ??
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Braden Glett
Ronald Taylor
Donald S Brant Jr