Re: QMX build troubleshooting
Oh, my. Then you're going to spending time on the main board. Lots of places to look. I'm sorry.
Something easy - just unsolder the finals. After that, if the short is still there, it's a matter of tracking it down.
It's a pain to troubleshoot SMD, I know. I design it every day and I hate troubleshooting my own designs. I always pray I didn't make any mistakes. LOL.
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Re: QMX build troubleshooting
The 12v short is without the boards installed.
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Re: QMX build troubleshooting
Wow, that's not good. And if you unplug each power supply one at a time? Need to find out which one is blown. They both have the +12vdc going to them.
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Re: Power out on 60 mtr QCX+
Hi Everyone
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Thanks for all you advise and comments on my low power issue on my newly built QCX+ for 60 mtrs. After a lot of time playing around with the LPF I decided to restore all the toroid values to those in the assembly instructions, and then just removed 2 turns from L3 and my power went up from 1.5 watts to 2.5? watts, using 13.8 volts. I played with the coil spacings but was unable to improve the output so I have decided to leave it with a 2.5 watt output.
Thanks for all your help and hope to catch you the wireless soon
73 Keith G4TJE
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3D model of QMX+? - To 3D print front and rear covers
Hi all,
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Having real struggles to find an existing cover(s) for the QMX+. All the ones are see are for the QMX. I can model some up easy enough but looking for a 3D model of a the QMX+ itself to model these around. I could model something close enough but looking to save some time.
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Thanks
Colin
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Re: QMX build troubleshooting
Started following this WIKI
/g/QRPLabs/files/QMX%20PSU%20pinout/QMX%20Pinout%20Drawing.pdf
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And when I did the following:
1) Checking all pins for shorts to ground are a good pre-first power check.
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I noticed I have continuity to ground on the +12V pins.
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Re: QMX build troubleshooting
Lift one side of it. If the rig powers up, that's your problem.?
It's an easy check, but make SURE your voltage is under 12 volts in.
If your supply surges, it will blow the 3.3 volt regulator.
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Re: QMX build troubleshooting
Check D109 on plug-in PCB #2, the 3.3 volt regulator.
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Re: QMX build troubleshooting
I built it for 12v and I had the PSU at 10-11v.
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Re: QMX build troubleshooting
How much voltage, EXACTLY were you using to power the radio?
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Hello Richard
My original aim for the QDX-M was to make versions for 160, 630 and 2200m, which are not suitable for the QDX because of the difficulties with PIN diode switching such low frequencies. However I got sidetracked by many other projects which is why I still did not go through the process of building and documenting one for each band. So at the moment it would be an experimental thing for you. The filters will not differ much from the 80m filter in the QDX 80-20m version, and this would provide a good starting point. The firmware only needs adjustment of the Band Configuration screen for the desired band.?
On Wed, Apr 23, 2025 at 2:39?AM Richard Katsch via <rkatsch= [email protected]> wrote: Hi All,
I have a plan to build a QDX-M for 80 metre FSQ activities. The QDX-M appears to be ideal for this with it's clever non SSB method of producing the tones required. However, the web page shop only lists 10,11,12 metre bands at the moment. After looking at the circuits for the QDX and QDX-M the changes for 80 metres would seem to be:
1. Use the low pass filter design for 80 m from the QDX. i.e change the inductors and capacitors in the QDX-M to be the same as the 80 m filter in the QDX.
2. Change the inductor in the QDX-M (L12) so that it resonates with the 56 pF capacitor at 3.6 MHz.
3. It looks like L14 remains the same for all bands.
So my question is: Has anyone done this and are there any steps I've missed, and can I buy a QDX-M kit with all the appropriate toroids, inductors, and capacitors? I'd like to buy one QDX-M for 80 metres and one extra set of components to change the unbuilt 10 metre QDX-M I have to 80 metres.
Apologies for the long and involved post.
Best Regards
Richard Katsch VK2EIK
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Re: QMX build troubleshooting
In firmware update mode only the linear 3.3v regulator is being used, there is no 5v rail and the buck converter regulators are not being used. See this article in the wiki for start up process.
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It is possible that you have a short on the 5v rail. ?There is a test process for the plug in buck converters in the wiki. ?Check the board for shorts on the voltage rails without the plug in converters connected and proceed from there.?
73 Nick G0OQK
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Re: QMX build troubleshooting
On Wed, Apr 23, 2025 at 04:52 AM, <f4jvu@...> wrote:
tried to start the radio by pressing the left encoder
Sounds like the short happened when pressing the encoder. Start looking there. The clearances are incredibly tight in the QMX, and it's a reasonable place to start.
Beyond that, I can't begin to suggest how to determine what was damaged by the high current draw.
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--
72 de N4REE, Bob Easton - QRP CW forever
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Re: Newly assembled QMX, SWR=1.5 with dummy load
Thanks Jerry,
I had a load of 2W 51R SMD resistors so using 4 in a series parallel arrangement gave me 8W power handling.
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Another way to do the power calculation is Vpk * Vpk / 100, that's practically mental arithmetic, or if you have a scope that measures the peak to peak voltage Vpp * Vpp / 400.
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This simple little dummy load come peak V measurement come attenuator was the best thing I made to help with testing a QMX.
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Incidentally the 2K5 resistor is 1k0 + 1k5.
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QMX build troubleshooting
Hello,
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I completed building the QMX yesterday. The initial plug in went smooth, no smoke no current draw.
I booted the QMX into update mode, put the firmware on it no problems at all.
Then I removed and re-inserted the dc plug and tried to start the radio by pressing the left encoder, suddenly I saw big current draw (stupidly i forgot to limit my power supply) it went up to something like 7 amps, so I unplugged it immediately. I dint see any smoke but the device did get hot in some areas. Visually I do not see anything burned on any of the PCB.
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So now, when I plug the radio in the DC plug nothing happens until I press the left encoder which creates a short and puts the power supply into constant current mode. (This time limited...)
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Can anyone please advise for any troubleshooting steps?
I put some pictures of the boards in attachment.
Thank you.
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Re: QMX only hearing static
It may be irrelevant to your case but something similar on another QRP labs receiver was recently traced to the MS5351 emitting narrow band noise instead ?of a single tone ?carrier on receive LO frequencies which resulted in loud static in the speaker
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Try to listen to the MS5351 receive output signal on another CW/SSB receiver. ? If you have signal strength but no CW tone that¡¯s the issue ?
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I have recently seen unstable 1pps on my QLG2, used for a GPSDO
The QLG2 has a minimum of 10 fixes, tracking 17 vehicles and signal strength
35 - 40 on an external mushroom aerial.
The 1pps suddenly jumps to a slightly shorter perid than 1s that throws the
PSDO into holdover.
Has anyone else seen this behaviour? Is it a duff GPS engine. Could it be a
software glitch in the QLG2 ?
Ideas on a $5 bill :-)
73 Mike
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Hello, I've just joined the forum and was ploughing through the 100+ emails I've received
while waiting for my QMX+ to arrive..
Randy
? I think it might help to explain how this thing is meant to work. So here's my shot at it:
? When it's powered up and the processor turns Q109 on for the first time there is no current
flowing through L102, and being an inductor it tries to keep it that way, but of course
doesn't succeed. So the current increases, causing C106 to charge up and some current to
flow through R114 and Q110, via "gnd" and back to the power supply.
? When the voltage across C106 reaches the required value the processor turns off Q109. At
this point L102 doesn't want the current to change so it supplies the current from its
stored energy (remember I squared L). If we think in terms of conventional current, flowing
from positive to negative, then the current flows out of the RHS of L102, through R114 and
Q110, along the gnd wire and back up D107 to the LHS end of L102. While it is doing this
D107 is forward biased and so with its anode connected to ground the cathode should be at
MINUS 0.6v approx.
? The fact that the D107/L102 junction is not swinging negative suggests that either
there is no circuit around the components described above, and hence no current through
L102, or that L102 is not storing the magnetic energy, either because its got a duff
core or a shorted turn.
? As an aside I see from the cct diagram that C106 is only rated at 10V so the voltages
you show are pushing it to its full rating.
? Good luck with it.
? Keith, G0GNL
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On 22/04/2025 23:39, Richard Katsch via groups.io wrote: I have a plan to build a QDX-M for 80 metre FSQ activities. The QDX-M appears to be ideal for this with it's clever non SSB method of producing the tones required. However, the web page shop only lists 10,11,12 metre bands at the moment. After looking at the circuits for the QDX and QDX-M the changes for 80 metres would seem to be:
1. Use the low pass filter design for 80 m from the QDX. Richard, The QDX-M has not featured much in this group. I guess it is for more specialised users, the QDM came out soon after and little has been added to the QDX pages. I bought one because the diode switching is omitted, theoretically giving a little more gain on high frequencies, and the possibility of use at LF. I'd think the standard QDX is better for general use being multiband and band variations better documented. You could miss out some unwanted bands. The QDM LPF will not be much different than the QDX ones but maybe the RX filters will vary. The multiband QDX RX filters are adjusted because of stray capacitances and other interactions. 73 Alan G4ZFQ
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Re: Another good solar description
Thanks Ed for your document. Helping to understand the sun effect on our hobby. ?
73, Ben?
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N4REE - Bob
Bruce Akhurst
Mike