QRPLabs@groups.io

Factory Reset?

Should I do a Factory Reset of my QMX after updating the firmware to 1_00_017 ?

Re: Wall Wart Tests

Very good point about the float voltage. ?I took another look at the three examples I'd posted earlier, simply probing both sides of the output with no ground path other than the two 10x probes themselves, then adding a resistor to ground on the negative side. ?Floating, both switchers show a 160 V p-p 60 Hz wave superimposed on both outputs, essentially full line voltage; introducing a 100k ground resistor reduces this to about 30 V, indicating a 400k impedance from line to output. ?The transformer-based supply starts out with 8 V of 60 Hz line coupling (probably capacitively coupled across the transformer) with only the probe loading, reduced to 2 V by adding a 1M ground resistor. ?I added photos of these measurements to the album.

I guess best practice if using an ungrounded wall wart would be to make up all connections first, with the radio definitively grounded, then plug the wall wart into the mains. ?Doing the barrel connector last there'd be a danger of contacting the positive terminal first, discharging the float charge through the radio.

Re: Another QMX Receive Issue Thread

#118377

I was JUST reading that and about to post that this issue sounds a lot like the symptom describes.? My unit shipped Dec 13, after the whole fiasco in Nov (Oct?) and I assumed it had the fixes.? Well, crap.? Any tests recommended to verify this is indeed the issue?? But it sounds like I may be replacing a fried "IC402 with a new 74CBT3253" as well as installing the?1N4148?

Show quoted text

Symptoms are: lack of audio; running the RF Sweeps etc in the terminal tools shows nonsense low audio values. It is important to note that there are multiple possible reasons for no audio, most issues are attributable to improperly installed toroids, specifically failure to properly remove enamel and ensure a good electrical connection. However if you become certain that you have a loss of audio then this indicates that the parasitic oscillation (on a transmit) has destroyed IC402 and it will need to be replaced with a new 74CBT3253.

This modification is a preventative measure, it prevents the occurrence of destructive parasitic oscillation. If your IC402 is already damaged, the diode won't fix it; you need to replace IC402 AND then install the diode.?

Re: Another QMX Receive Issue Thread

#118376

The radio going deaf sounds a lot like this issue:

I don't see that mod on the board photos you posted.

Re: Another QMX Receive Issue Thread

#118375

Also, Rev 2 board (so the paperwork says), 12v, order?73417 fwiw, received pre-built assembled in case.

Disassembled and took photos of boards

Another QMX Receive Issue Thread

#118374

QMX Low Band, bought pre-assembled.? Have not even opened the case to peek inside.?

I have made contacts with it, as recent as about a week or so ago, both CW and FT8.? Have had .014 on it.? This weekend I loaded .017 on it (after the fix) and all of a sudden it went deaf.? I think when it did was coincidental.? AGC on, off, variety of configs I've seen in threads here and just tried myself, no change.? I can hear the faintest signals sometimes, but swapping the cable between another radio where I can confirm W1AW is on 7/14.047.5 at +10 over, it should be blowing out my eardrums and I can't even hear it, only static.

So I loaded up diagnostics.? It looks like everything's right until I get to the audio/rf filter sweeps, and guessing the image sweep should be a little more pronounced as well.? These look VERY abnormal, while the LPF sweep looks fine as do all the voltage levels in diagnostics.

Put .014 back on it, factory reset, no change.? I haven't dropped it, as far as I know nothing irregular has happened.? I'm guessing I'm going to have to open this thing up, a task I dread doing hence why I bought pre-assembled, and not having assembled it I don't know much about its inner workings.? Any guidance based on what I've given?? I have a multimeter and a brave heart.? Also a good soldering iron and a steady hand but I reeeally don't want to have to use it if I don't have to.

Thanks in advance
Jason KO4NDP

LPFs look good

Abnormal?

PTT/TX, SMPS looks ok I think?

40m audio filter sweep (80 looks similar)... not quite right...

RF filter sweeps, not quite right....

Re: QMX Receive suddenly stop working

#118373

Thank you for the suggestions. I finally figured out. The mos Q508 is shorten, which switches RX/TX. I already did the modification of adding a diode IN4148 as suggested by the official document. I suspect that I lifted SWR protection to 5 and was tuning the antenna. Any other thoughts why this happen?

Re: Wall Wart Tests

#118372

"I wish there would be means and ways to replace the SMPS Power Modules with plain, normal linear voltage stabilizers to avoid ensuing disaster of this kind. There could be a main 5 V rail and a 3,3V daisychained to it to avoid having to dissipate too much heat on the later one."

I've done exactly that.? Replaced the 5V and 3V3 SMPS 'regulators' with TO220 sized linear regulators on Vero board that fits in place of the original PCBs.? There's enough feedback to keep the processor happy. It can't turn the power on and off but there are things called switches that will do that.

It takes a bit more power and generates a bit more heat but works.

Chris, G5CTH

QMX FW #17 sometimes wrongly reads right paddle as left+right

#118371

Hi,

This started happening when I switched to FW #17 (and did a factory reset 
after that). I was previously using FW #14 and didn't have that problem 
(but now, after switching to #14, it sometimes, very rarely, occurs too). 
See for yourself:



It's always the right paddle, regardless of the setting of "Keyer swap".

I don't think it's a problem with the key -- it's a very simple mechanical 
construction.

It is intermittent. Sometimes dah works correctly, sometimes it inserts 
dits only at the beginning, sometimes it behaves like both paddles were 
pressed at the same time. Now I tried testing it once again and the 
problem disappeared as suddenly as it appeared.

Anyone else stumbled across this problem?

Re: Wall Wart Tests

#118370

On Tue, Feb 20, 2024 at 06:48 AM, Jeffrey W Moore wrote:

?The SMPS power modules in the QMX along with the firmware could get very confused and disaster could ensue.

I wish there would be means and ways to replace the SMPS Power Modules with plain, normal linear voltage stabilizers to avoid ensuing disaster of this kind. There could be a main 5 V rail and a 3,3V daisychained to it to avoid having to dissipate too much heat on the later one.

The price paid would be a higher power consumption of the whole rig, but let us be honest: the QMX with it's galore digital? functions is nowhere near of being a power savings champion, so a couple or two of miliamps lost in the process of linear voltage stabilization would not be of much concern, at least for me.

Getting rid of that sour feeling that some kind of ensuing disaster might happen just because the SMPSes could feel offended in some way or another would on the contrary mean much to me and to my inner peace of mind when turning the QMX on or off without having to hold each time doing so the fingers crossed and hope that everything will work out well...

It does work well, most of the time and for most of the users. But reading the numerous stories of ensued disaster happened to fellow QMX users makes me feel soooooo unsure whenever looking at the QMY, set aside turning it on or even off. It is just a bad feeling I have, no reason to criticize the design or function of the rig: just a bad, sour feeling. It is just those SMPSes: the idea behind them is genialy bright! I liked it from the start. But it's real world behaviour and the ensued disasters happened we read about in this forum every now and then? make me feel uneasy.

...confused...
73 de Razvan, dl2arl

Issue: QMX unable to shut down after loss of USB when using serial terminal interface

#118369

Minor, rare, not catastrophic?

If? my USB connection drops (connector quality / accidental unplug) while I'm in a terminal session for band setup, diagnostics, etc (in Putty for example) the QMX can no longer be shut down with a left encoder press, and a physical removal of the power cable is required.?

Is it possible to have terminal mode exit if the USB stack throws a host disconnect? I do wonder what would happen if there was a disconnected USB while a TX key was in progress? Would the TX stay keyed??

Andy

QMX 1_00_017 TX indication persists after transmission on new LCD driver version.

#118368

Hello,

Under certain conditions or procedures, while in DIGI mode? the LCD appears to freeze the power and S meter output after a transmit cycle, indicating that a transmission is still occurring, even though the radio is in RX mode (based on the expected sounds of the band on the audio output)?

A second transmit cycle will usually remedy the the issue - it's purely cosmetic and the radio seems to operate fine. It is however disturbing to look at the display and see a transmission in progress when the ears and waterfall say otherwise.?

UNFORTUNATELY, and I apologize, I am not able to reliably reproduce this bug feature, except that I see it on 17M and 20M, DIGI mode (not CW)? on WSJT-X, because that's where I usually operate. This did not happen with 1_00_014. No updates to WSJT-X have been made.

Have others encountered this? And can YOU reliably reproduce it? How?

Re: #qmx #firmware 1_00_017 AGC, S-meter, LPF sweep #qmx #firmware

#118367

@Hans,
Do you have any plans or schedule, for the release of the firmware? It's a little bit of a hassle for me to load a new one so it might be good to know in advance so I don't load the day before new one is coming...
Good job with that AGC!