Re: QSX project retirement
On Wed, Mar 19, 2025 at 10:56 AM, KEN G4APB wrote:
Hans said…..Sure! We are currently preparing 500 more of the 10W Linear kit. I have the PCBs on the way with FedEx and everything else is here in hand already!
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So what are all these going to be used with?
Hi? With all that gain, you can use it for HackRF kind of miliWatt SDR transceivers. Even with U4B baloon Tracker 73 DE muhsin TA1MHS
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Hi Sergey
My QMX works great with 1_01_003 firmware. I've calibrated it and SSB reports are very good. Thanks!?
Great!
Few problems:
1. Wattmeter indicator looks like very slowly responding to actual power in antenna. As if it is averaging for couple of seconds...
In version 1_00_003 the power meter reads peaks. Not averages. Then there is also a hold time. It may give the impression of responding slowly. In the display/controls menu you can configure the update rate and the hold time, so that you can customize how the power meter responds. So I suggest in the first instance, having a look at these features and see if you can set it up to your liking.?
2. When I use my usual PA with 1.3 input SWR (measured with NanoVNA) QMX tends to stop transmitting in several seconds due to SWR Protection. And SWR meter displays some big figures which do not exist in reality (checked with my standard SDR transiver and NanoVNA).
I think that there is now some issue with the SWR falsely reading large values at the start of an SSB transmission, which can trigger the SWR protection. I need to investigate this on my return from vacation.?
3. Nothing changes on PTT output during TX. 5V stays on the ring and 0V on the tip.?
If I understand from a different thread, you've got this configured correctly now by using PuTTY to access the hand configuration screen.? 73 Hans G0UPL
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Re: Help with partially fried QMX
Stan,
Thank you very much for your detailed reply. After trying some of your triage steps, I am observing that the GND, +12V, and VCC all exhibit continuity with each other on the compromised SMP board. It is important to note that male pins attached to the main board do not have this continuity, it is only present on the SMP board. I also did continuity checks on Q108 and see that all 3 leads have continuity. I'm unsure if this is a result of the blown component, or if it existed in some sort of compromised state prior to the failure.
I've also gone ahead and double checked all solder joints and looked for solder flakes or other potential areas that could cause unwanted connections. I'm still unable to find a bridge connection but will continue my search as I await my replacement components. Attached are some pictures of the places you suggested I inspect and labeled the pins showing continuity. I've also taken some photos of the area surrounding Q108.
Thank you again for your help and suggestions!
Austin K4HYD
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Re: QMX+ high pitch noise on power. Now dead.
I have rev 2. When I plug in the power it still shows as 12 on the board. It only draws power when I press the power button.
For that TVS diode (right alongside the power connector), the forward 0.6V drop is not the critical thing - it is the reverse breakdown, and I'm not sure if the 'diode test' function of a multimeter can test that.
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The first measurement I would do is to plug in the 12V power, and then measure the voltage (Vin) on the QMX board, perhaps on the center pin of the power connector.? If the voltage is down well below 12V, then that TVS diode has likely failed.? If it still is at 12V, and no power supply current draw, then the failure is likely elsewhere.
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Which rev of QMX+ board do you have?? The rev 1 with the SMPS power supplies on the little cards?? If so, you can test them separately via the procedure in the wiki.
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Stan KC7XE
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Re: QMX+ high pitch noise on power. Now dead.
For that TVS diode (right alongside the power connector), the forward 0.6V drop is not the critical thing - it is the reverse breakdown, and I'm not sure if the 'diode test' function of a multimeter can test that.
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The first measurement I would do is to plug in the 12V power, and then measure the voltage (Vin) on the QMX board, perhaps on the center pin of the power connector.? If the voltage is down well below 12V, then that TVS diode has likely failed.? If it still is at 12V, and no power supply current draw, then the failure is likely elsewhere.
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Which rev of QMX+ board do you have?? The rev 1 with the SMPS power supplies on the little cards?? If so, you can test them separately via the procedure in the wiki.
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Stan KC7XE
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Re: Help with partially fried QMX
On Fri, Mar 28, 2025 at 11:00 AM, Austin K4HYD wrote:
It's still unclear why the MOSFET would blow in this case as it's rated for 20V
The MOSFET would blow from over-current, not over-voltage.? And high current will happen if +5V is somewhere shorted to ground, or Q108 is turned on all the time, which causes zener D108, which is trying to keep the voltage down to 5.6V to conduct very strongly and perhaps fuse shorted in doing so.? A 12V short to the 5V bus would also cause a lot of current to go through Q108, at least until D106 fails shorted.
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Re: Help with partially fried QMX
Austin,
If your screen lighted up and Q108 blew without you pressing the power-on button, it means you have one or more shorts going on.? That display tab can cause shorts in the power supply, but I'm not sure it would do all of what you described.? Other likely places for power supply shorts to happen on QMX is solder bridging of some sort on the power connectors, either on the main board or on the small SMPS board.? If you didn't trim the connector legs that get soldered to the top of the SMPS, they are dangerously close to some of the SMPS components where solder bridging can occur.? There are also other close-proximity areas that could possibly short when you assemble the display board to the main board, such as around the encoder bodies, and at the back of the power connector.
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From a circuit point of view, to cause what happened to you, you had a short (or less likely, a failed component) that bypassed the power switch, and another that either held the PWM_5V line high or somehow shorted Vin or 12V to the 5V bus.? Perhaps there is a single fault that could cause both of these.
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One possible scenario is this:? A solder bridge or solder flake shorted the Vin pin to the PWM_5V pin, which are adjacent pins in connector JP101 (and on the SMPS card).? This combined with either a) a short to another adjacent pin, PWR_HOLD, or b) something holding PWR_ON low, or c) a Vin short to 12V.?? Any one of those combinations would put the Vin voltage on the +12V rail, and turn on Q108 full time, such that it tries to pull the 5V rail to 12V.?? Then zener diode D108 starts conducting strongly to try and hold the voltage to 5V, burning Q108 and the coil (and probably also shorting D108).? Meanwhile the display turns on from the 5V supply.
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It shouldn't be too hard to trace down the culprit(s).? Before putting in new SMPS, do measure the resistance between Vcc and Gnd on the main board - it should be a few k-ohms.? If it measures in the low ohms, you have some sort of failure on the main board that you need to fix.
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And if possible, use a 250mA current limit on your power supply until you get a full successful power-on and startup.? This is highly recommended, along with using a lower voltage, like 7V for initial power-on testing.?? That would have saved you from burning the parts, and will save you in future tests from burning additional parts if you don't have the problem(s) fully fixed.
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Stan KC7XE
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Re: QMX+ high pitch noise on power. Now dead.
I just checked the diode and it seems to be fine with a 0.6v drop.
Where is D110 on the qmx board? I can try to check its state.
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?
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 #SSB Firmware beta 1_01_003 release
#qmx
#ssb
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Re: #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
Hello,
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I am doing some experiments with the qmx filter sections. E.g. I bridged the BPF and LPF section by a cap.
I wanted to test, how flat the sweeps are without any filter.
The results are good enough for testing the correct function of the filters.
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But I noticed some strange effects, that could give a hint for the calibration issues:
Some sweeps contain very low values. When I change the borders of the sweep i get good results.
Are there are numerical unstabilities or overflows in values?
By design, the QMX also contains some birdies, maybe they could have such an influence on measurements? You can compare these two images on similar frequency ranges:  ?
This is all done with the 27 firmware.
Here we didn't notice the bug, because we never played with the frequency ranges.
During calibration, or my experiments, it becomes visible.
(Just my theory)
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Vy 73 Peter DL4PJ
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Re: #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
On Fri, Mar 28, 2025 at 11:00 AM, Chris wrote:
I tested the quality of the SSB transmission today. A standard electret microphone with a mic gain of 55 and a compressor of 3-5 and at the end. The receiver was an FT-817.
Very nice quality, Chris.? Thanks for posting!
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If you just ordered it, it's a Version? 3.? ?Hans said at the start that he would not ship 3 until the stock of older versions is empty.? I ordered? weeks ago and it was a 3.?
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Printing in color will cost a fortune. Even mono isn't cheap via online printers.?
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I have the build manual on both a large screen and an iPad.? It works well that way.
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https://www.allaboutcircuits.com/technical-articles/introduction-to-the-feed-forward-linearization-of-rf-power-amplifiers/?user_mcid=3b7c12b4be
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Re: #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
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Help with partially fried QMX
Hello, I recently just fished putting my QMX Rev 4 kit together with the windings necessary for 12v input. As I was going along I verified I all continuity checks as instructed and verified no pads were bridged. Upon attempting to power on the device, I connected my 12v power supply to the barrel connector. The screen immediately lit up and I had black rectangles across the top half of the screen. A second or two later I started seeing smoke, heard a pop, and the screen went dark. Upon further inspection, I was able to discern that the Q108 MOSFET on Plug-in PCB #1 blistered and exploded. The L101 inductor nearby also looks a little singed but the enamel coating does not appear to be compromised. I do not see any other areas of the device that appear to have been compromised or damaged.
I was wondering if anyone may be able to assist with what actually went wrong here. I have ordered a new power supply board as well as a replacement MOSFET to try my hand and replacing the bad component.
My current theories on what went wrong are:
- I am missing a bad solder joint somewhere that caused the issue, still attempting to find one if so. It's still unclear why the MOSFET would blow in this case as it's rated for 20V and my power supply used is only capable of 12V out.
- There is a step in the instructions that says to bend a tab of the LCD screen at about 45 degrees to clear the L101 inductor. I noticed that this appears to have been discolored possibly due to heat. There's a good chance that this tab was not bent quite enough and made contact with the top face of the L101 inductor, though I don't think the top face is conductive. This could have resulted in a short to ground?
- My winding on the RWTST Transformer is somehow incorrect.
Image upon powering up. Seconds before smoke and pop.?
Note: I did not press the left dial in, the screen lit up as soon as power was supplied to the barrel connector.
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Re: #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
I tested the quality of the SSB transmission today. A standard electret microphone with a mic gain of 55 and a compressor of 3-5 and at the end. The receiver was an FT-817.
73 Chris
https://youtu.be/fImxAz-MeQ4
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Re: QSX project retirement
I know about the wattage differences compared with S-meter readings, etc., but... is there any chance the QMX+ will have a full 10W output like the QSX was spec'd to have?
The probability is certainly non-zero. But I don't have any concrete plans for a 10W QMX+ at the moment.?
Bear in mind that the QSX would have had 10W output. But the QMX+ has CESSB, giving it effectively a 4 or 5 dB advantage. Which effectively makes its power a little more than 10W. So a QMX+ transmitting speech is at least comparable to a QSX transmitting speech at 10W SSB. Before anyone asks what about QSX with CESSB: I believe it is very unlikely that the QSX would have been able to do CESSB.?
73 Hans G0UPL
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#QMX #SSB #calibration A note about spurious PA power after IMD optimization on a band is over
#qmx
#ssb
#calibration
I don't know if any of you has noticed anything similar: while performing the SSB calibration on a band-by-band basis (using the "O" option) I noticed that at the end of the USB/LSB IMD Optimization step of each band, the power out is not put back to zero. I read between 0.5W and 1.2-1.5W on some bands, and again, this is after the IMD optimisation has ended for that band. If I CTRL+Q, then power is reset back to zero. If I get back into calibration, power is still zero. If I do calibrate another band (still with 'O') , the calibration succeeds but at the end the PA is not shut down completely.
Now, I think this is hardly enough to put the finals under any substantial strain, if it stays like that for a couple of minutes at most. But I wonder if the few cases of fellows who "left the calibration running and went out for a walk" and then found their finals toast could not be due just to this glitch, i.e., the PA remaining keyed for several minutes, even at lower-than-max power, which might be enough to cook them up, under certain constraints.
Has anyone else noticed this? I guess a consistent set of measures of this effect (if it is not just in my QMX+ specimen) might help Hans pin-pointing the issue when he is back from vacation.
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Hope this helps.
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72/73 de Enzo M0KTZ
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Re: QSX project retirement
I know about the wattage differences compared with S-meter readings, etc., but... is there any chance the QMX+ will have a full 10W output like the QSX was spec'd to have?
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73, Norm/KC1BMD
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Probably a waste of paper either way.
Most of us have a laptop or small desktop that can sit on the workbench,
better than paper in that you can quickly search for a specific part.
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I'd just print out a few key pages that you might want to mark up.
For example, print the BOM, and use that to inventory all parts in the kit as a first step.
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No hint that there are any hardware changes imminent.
Hans will be busy with firmware for some time to come.
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Jerry, KE7ER
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On Fri, Mar 28, 2025 at 04:56 AM, Mike M1BVA wrote:
I've just ordered a QMX+. I want to print the assembly manual out. I'm assuming it'll be a Rev 3 PCB but I'm wondering if I should wait until the kit arrives to be sure and not 'waste' paper and ink?
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Ray D Congdon
Chris
Norm - KC1BMD