Your C107 is a 6.3 V spec. (I can see by the one on the 3.3 V board - not an issue there.) I had one blow early on and it took out a few other things on the 5 V SMPS. I repaired it, but testing showed continued problems. I bought a new set of SMPSs from Hans and I've had no issues since. Hans went to a 10 V spec C107 later and I haven't heard of more problems like yours. I believe some of the 6.3 V spec ones were more like 5 V and that's why it blew.?
Anyway, there is a good chance that something else is damaged, hopefully only on the PS boards. As recommended by others, check the Vdd and Vss and +12 V resistances after you remove the SMPSs. If those resistances are good, then I would recommend you simply buy a new pair of SMPSs from Hans rather than try to repair the ones that are damaged.?
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73, Dan? NM3A
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Re: QMX only hearing static
On Mon, Apr 21, 2025 at 10:06 PM, Kai Bouwman wrote:
When I tested IC 502 and 501 pin 1 on both of them was ~1.6V and pin 4 was at 3.3V
Very strange. Please check it you really tested pin 4. Pin 5 is on the same side of the case and is connected to 3.3V.
The signal from pin 1 is going to pin 4, for IC502 with the same timing and for IC501 inverted. But 1.6V is ok. So the question is, is IC402 half ok (working CLK2) and half broken (dead CLK0 and CLK1)?
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Did you inspect like I wrote in an early post?
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A have no clue how to debug more from remote. I see low probability for a half broken IC204 and never saw a broken IC403.
I would contact Jeff Moore and ask for Help.
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73 Ludwig
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Re: Newly assembled QMX, SWR=1.5 with dummy load
Thank you. I'll try that tomorrow.
On Mon, Apr 21, 2025 at 11:45 AM, Jan Szumiec wrote:
The L401 transformer has some looseness on one of the windings (1mm) - would that matter?
No, that won't hurt anything, and does not affect transmit (T401 is only used on receive).
Also, it appears that the SWR is a function of power. It is greater when I measure it at 10/20% and lower when it is 50%. Is this normal?
No, SWR is not a function of power, if everything is operating correctly.? The SMA terminator from your nanovna kit should work fine at the lower powers, but is not built for 5W - so don't use it with full power, or you may burn it out.
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The SWR and power displayed by the QMX are both read from the bridge circuit, of which T507 is the principle part.? What the CPU actually reads from that bridge is the peak forward and reverse voltage (divided by 10), from which it calculates power and swr.? So if one of the solder joints to T507 is a bit 'flaky' or 'cold', it could cause either the forward or reverse voltage to be incorrect or 'noisy', causing incorrect measurements.? So check those and re-flow them, leaving the iron on the connection for several seconds in case there is still some enamel that needs burned away from the wires.? [There are also SMD resistors, 2 diodes and 2 capacitors in that bridge circuit - it is less likely, but if one of those have been disturbed, it could also cause this issue.]
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Re: Newly assembled QMX, SWR=1.5 with dummy load
On Mon, Apr 21, 2025 at 11:45 AM, Jan Szumiec wrote:
The L401 transformer has some looseness on one of the windings (1mm) - would that matter?
No, that won't hurt anything, and does not affect transmit (T401 is only used on receive).
Also, it appears that the SWR is a function of power. It is greater when I measure it at 10/20% and lower when it is 50%. Is this normal?
No, SWR is not a function of power, if everything is operating correctly.? The SMA terminator from your nanovna kit should work fine at the lower powers, but is not built for 5W - so don't use it with full power, or you may burn it out.
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The SWR and power displayed by the QMX are both read from the bridge circuit, of which T507 is the principle part.? What the CPU actually reads from that bridge is the peak forward and reverse voltage (divided by 10), from which it calculates power and swr.? So if one of the solder joints to T507 is a bit 'flaky' or 'cold', it could cause either the forward or reverse voltage to be incorrect or 'noisy', causing incorrect measurements.? So check those and re-flow them, leaving the iron on the connection for several seconds in case there is still some enamel that needs burned away from the wires.? [There are also SMD resistors, 2 diodes and 2 capacitors in that bridge circuit - it is less likely, but if one of those have been disturbed, it could also cause this issue.]
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Update:
The stereo splitter was for the mic/PTT connector and to plug the Pro 7 mono mic connector into.
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Re: QMX only hearing static
When I tested IC 502 and 501 pin 1 on both of them was ~1.6V and pin 4 was at 3.3V
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I plugged my Heil Pro 7 (IC) with AD-1-IC into my QMX+ with version 1_01_003 Firmware. I adjusted the mic gain with the hardware test from my PC and later from the QMX. I made my first contact with a POTA station in Houston from Colorado on 20m, with difficulty because of my weak signal. Although I have tried, I have yet to make any additional contacts on 20m.
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I plugged the Ad-1 stereo earphone connector directly into the QMX, but had to use a stereo splitter to isolate the ring and ground connections. While the ICOM radios like the 7610 supplies an 8 volt bias and the QMX 3.3 volt bias, the Pro 7 IC seems to work OK with the QMX. I use VOX.
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Using a Li-ion battery to power the QMX, I plan to drive over to a ham buddy who knows my voice and make further audio adjustments and check the transmitted signal quality. ?I will post my settings here after doing so.
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Re: QMX+ kit build - RX birdies on Digi and loud wide tone on CW
Thanks for the suggestions. I will do some more testing taking these into account.
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Kind regards,
Kev G0AKH
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Re: QMX+ kit build - RX birdies on Digi and loud wide tone on CW
I see these exactly birdies on 15m in didi when attached to USB. I can lower them with clip on ferrites and USB cables with better built in common mode isolation but not fully remove them.
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I'm very interested in whether folks have good mitigation suggestions for this. I'm quite certain that it's aliasing of the cat control signals. They disappear completely if you disable CAT control and only watch the waterfall in WSJT-X.
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Greg
N1TR?
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Re: Newly assembled QMX, SWR=1.5 with dummy load
I'm using an SMA terminator?which came with my NanoVNA.
Are you using a dummy load or a resistor for a dummy load? If using a resistor what type? It would make a difference as some types of resistor are not suitable for RF.
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Re: Newly assembled QMX, SWR=1.5 with dummy load
Are you using a dummy load or a resistor for a dummy load? If using a resistor what type? It would make a difference as some types of resistor are not suitable for RF.
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Re: Newly assembled QMX, SWR=1.5 with dummy load
The resistor is 50.7 ohm (if you trust the $20 multimeter), and 50.9 ohm with the cable attached. Solder joints appear to be solid, but I'll inspect it once again when I find my magnifying glass. The number of windings is correct. The L401 transformer has some looseness on one of the windings (1mm) - would that matter?
Also, it appears that the SWR is a function of power. It is greater when I measure it at 10/20% and lower when it is 50%. Is this normal?
Thanks, J
I concur with the previous recommendations.
SWR into a dummy load from the QMX should show 1.0x:1 on the lower bands, increasing to perhaps 1.1x on the highest band.
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Re: I think I broke my QMX...
Mike,
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Here's an explanation of why D516 was added:
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If I were debugging this, I would first triple check that all the mods have been done correctly
with no unexpected shorts.? It's hard to tell from the photos.
A short could easily silence your receiver.
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Next, I might apply a receiving antenna (maybe 20 ft of magnet wire across the room)
to the bottom of L406 where it is tied to pin 5 of IC408, see if the receiver works.
If it works, we know that IC408 did not blow for some reason.
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Then try applying that receiving antenna to the drain of Q508 where it connects to C509,
see if the receiver still works.? If it does not work the problem is around Q508 somewhere.
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You might wait a few hours first, see if there are objections from others to doing this.
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A question for the group:
It looks to me like the entire receiver front end is operating at 50 ohms, being terminated?
by two effectively parallel 100 ohm resistors at R413 and R414.
So the series 1nF cap at C509 is driving a 50 ohm load.
Impedance of a cap is 1/(2*pi*f*c), so at 1.8mhz that's 1/(2*3.14*1.8e6*1e-9) = 88.5 ohms,
and likely not an issue since the low bands have so much atmospheric noise.
Would IC408 be less prone to damage if C445 were also at 1nF instead of 0.1uF?
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Jerry, KE7ER
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On Mon, Apr 21, 2025 at 10:59 AM, Jerry Gaffke wrote:
D516 prevents any large voltage spikes from from destroying the receiver front end when transmitting.
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It looks like both of the SMS boards have suffered a catastrophic failure.? Not just the failure you mentioned if the first board, but also on the second board.?
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I would remove those and check the main board with a dmm to ensure they're isn't anything else wrong.?
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I am using an external mic and the beta version -003 for SSB. Even the slightest tap or shuffle on the desk with my QMX+ causes the VOX to trip. I am confident the external mic is not causing the VOX to trip. Would Hans spur removal still work if I removed the QMX+ internal mic and would that get rid of the unwanted VOX trips? Or do you think Hans could isolate the internal mic from the VOX detection in firmware?
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Hi all,
Yesterday, I finally found the time to finish building my second QMX (Rev.2, 10m - 20m). Initial setup was easy, and after loading the latest firmware, all tests ran smoothly.
Today was its first use, which was also successful with a few FT8 QSOs. But after about 3 hours, the QMX said goodbye with a loud pop. C107 looked like the picture below:
I can't identify a cause for this defect. The QMX is built for 9V and was powered by the stabilized 9V output of a TelentCell LF4100. The antenna was a precisely tuned vertical.
Will replacing C107 be enough? I'm worried about Q107. Could the burn that can be seen in the picture have been caused by C107, or is Q107 also defective?
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73, Joerg DG0JDE
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Re: I think I broke my QMX...
Mike,
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What you are seeing sounds like correct behavior to me for Q508 when in receive mode with RX at 3.3v.
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L502 holds the source pin at ground for DC, any received signal is in the microvolts, and very hard to detect.
With the gate pin at 3.3v, the transistor is on, so the weak pullup resistor at R510 is overpowered and the drain pin is also at ground.
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D516 prevents any large voltage spikes from from destroying the receiver front end when transmitting.
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I'm not sure how to cure your problem, but Q508 may be working correctly.
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Jerry, KE7ER
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On Mon, Apr 21, 2025 at 10:19 AM, Mike, KL7MJ wrote:
Stan,
I¡¯m seeing 0 on S and D, and 3.3 on the gate.?
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Re: I think I broke my QMX...
Stan,
I¡¯m seeing 0 on S and D, and 3.3 on the gate.?
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Re: Power out on 60 mtr QCX+
Keith, you should be able to get a good 4 or 5 watts out on that band. Have you tried adjusting the lowpass filter toroid windings yet? I would suggest that you start with L3 and spread the turns as much as possible. If the power increases as you spread them and is still increasing when you get them spread as far as they will go, then remove one turn from L3 and check again. The best way to remove a turn is to heat the outer wire connection and lift it out of the hole. Then unwind a turn. Don't cut the wire and don't try to clean out the hole. Just tack solder the wire to the top of the board. If you have to remove another turn, do it the same way. When and only when you get them where you want them to be, trim the wires and reinstall. I usually just solder them to the top of the board instead of risking board damage trying to clean out the holes. Next, squeeze the turns on L2 a bit. If that increases power, squeeze them further until the power peaks and finally spread the turns on L1. In all cases, if the opposite happens when adjusting turns spacing just go the other way. You will need to play with all of them probably. Stop when you get to 4 or 5 watts. There is no advantage in going beyond 5 watts and it will only serve to shorten the life of the finals.
It should?not be necessary to remove more than one or two turns maximum from L3.?
Good luck .. .73 .. Ron
Hi
I recently built a QCX+ for 60 mtrs. Everything works ok except that I only get about 1.5watts out into a dummy. load.? Just wondering whether any one has built a QCX+ for 60mtrs and what power? out? that is expected for this band .
look forward to any replies.
Keith G4TJE
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Re: I think I broke my QMX...
Mike,
I can see several cold solders and tiny bridges in your photos. I suggest you clear those first.
73! de Bekir TA2RX
21 Nis 2025 Pzt 19:49 tarihinde Mike, KL7MJ via <alaskamike= [email protected]> ?unu yazd?:
I misread the value for L503, so I replaced it with a 47uH inductor, with no change in the receiver.
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Richard Dyer
Jason
Ronald Taylor