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#qmx Power not staying on after Q103-Q104 fix #qmx

 

Folks,

my QMX had the Q103-Q104 issue. I managed to unsolder and move Q103, and now the short has disappeared. I also replaced D101 with a THT one (it went off at first power-on, I had not checked for the short beforehand, my fault!), and I put a wire to connect the two sources? of Q103 and Q105, as the pad of the source of Q103 did not survive the surgery.

Now the continuity tests work as expected. The problem is that the PCB does not stay turned on. If I keep the left button pressed, the CPU boots and I can see the device appearing as a USB drive, but it powers down when I depress the left button. My impression is that Q104 might be the culprit, but before replacing it I wonder whether anybody has seen anything similar? I have read through the related topics in the reflector, and I don't seem to be able to find a specific answer there, hence this post.

Thanks in advance

72/73 de Enzo M0KTZ
 

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Enzo have you installed the Firmware yet?
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73
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Ian G4GIR
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----- Original Message -----
From: Enzo M0KTZ <m0ktz@...>
Reply-To: <[email protected]>
Sent: 12/09/2023 14:32:16
Subject: [QRPLabs] #qmx Power not staying on after Q103-Q104 fix
Folks,

my QMX had the Q103-Q104 issue. I managed to unsolder and move Q103, and now the short has disappeared. I also replaced D101 with a THT one (it went off at first power-on, I had not checked for the short beforehand, my fault!), and I put a wire to connect the two sources? of Q103 and Q105, as the pad of the source of Q103 did not survive the surgery.

Now the continuity tests work as expected. The problem is that the PCB does not stay turned on. If I keep the left button pressed, the CPU boots and I can see the device appearing as a USB drive, but it powers down when I depress the left button. My impression is that Q104 might be the culprit, but before replacing it I wonder whether anybody has seen anything similar? I have read through the related topics in the reflector, and I don't seem to be able to find a specific answer there, hence this post.

Thanks in advance

72/73 de Enzo M0KTZ

 

No I haven't. I was under the impression that you didn't need to keep the left button pressed to load the firmware. Or at least this is how I read the assembly manual. Please accept my apologies if this in incorrect.

If I press the left button momentarily and release it, the board shuts down. That's the issue HI.

72/73 de Enzo M0KTZ
 

It may or may not be Q104. I had exactly the same issue/symptoms on a
QMX that had firmware loaded. Turns out I had blown the PWR_HOLD port
on the MPU. I had to hardwire Vdd to the gate of Q104 to get it to
stay up. It won't shutdown now as PWR_HOLD is permanently on. It hangs
at the "Shutdown" message and I simply pull the plug or switch the
power off. Not saying your issue is the same but you can check by
measuring the voltage at the gate of Q104 while the left encoder is
down and again when it is released.

-mike/w1mt

On Tue, Sep 12, 2023 at 9:59?AM Enzo M0KTZ <m0ktz@...> wrote:

No I haven't. I was under the impression that you didn't need to keep the left button pressed to load the firmware. Or at least this is how I read the assembly manual. Please accept my apologies if this in incorrect.

If I press the left button momentarily and release it, the board shuts down. That's the issue HI.

72/73 de Enzo M0KTZ
 

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OK Enzo
?
You need to press the left button briefly the Flash drive appears, drag the downloaded firmware to the Flash Drive and it will install, don't touch the left button again. I think the display will come alive once the Firmware gets installed. If you press the left button it will turn the QMX off.
?
Hope this helps.
?
73
?
Ian G4GIR
?

----- Original Message -----
From: Enzo M0KTZ <m0ktz@...>
Reply-To: <[email protected]>
Sent: 12/09/2023 14:59:31
Subject: Re: [QRPLabs] #qmx Power not staying on after Q103-Q104 fix
No I haven't. I was under the impression that you didn't need to keep the left button pressed to load the firmware. Or at least this is how I read the assembly manual. Please accept my apologies if this in incorrect.

If I press the left button momentarily and release it, the board shuts down. That's the issue HI.

72/73 de Enzo M0KTZ

 

Also, when it "powers down" does the USB drive disappear? I seem to recall the current drawn goes way down when you release the left encoder but the drive was still there and I was able to load the firmware...

-mike/w1mt
 

So, that is exactly the problem: if I press the power button briefly, I see about 200mA going into the board (input voltage at 9V, not at full 12V), but the boards shuts down as soon I release the button (and the current drawn goes to zero). That's why I thought Q104 could be toast.

If I keep the button pressed, I see the USB drive appearing, I can mount it and can see the EEPROM file in there. Luckily I am able to use the laptop with my left hand, while the right one is keeping the QMX left button pressed HI.

I haven't tried loading the firmware yet, as I reckon this is not normal behaviour: the assembly instructions clearly state to press the left button momentarily, not to keep it pressed while loading the firmware.

Hope it's more clear now.

Thanks in advance

72/73 de Enzo M0KTZ
 

OK Mike, this is most useful. I will check PWR_HOLD as well. I reckon it should go up as soon as the CPU boots (and the CPU does boot, indeed). If PWR_HOLD does go up at boot, then Q104 is probably toast.

Thanks a lot.
 

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?
Ok Enzo
?
Yes that is clear now. That wasn't how I read the first mail.
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Good luck hope you sort it.
?
73
?
Ian G4GIR
?

----- Original Message -----
From: Enzo M0KTZ <m0ktz@...>
Reply-To: <[email protected]>
Sent: 12/09/2023 15:15:14
Subject: Re: [QRPLabs] #qmx Power not staying on after Q103-Q104 fix
So, that is exactly the problem: if I press the power button briefly, I see about 200mA going into the board (input voltage at 9V, not at full 12V), but the boards shuts down as soon I release the button (and the current drawn goes to zero). That's why I thought Q104 could be toast.

If I keep the button pressed, I see the USB drive appearing, I can mount it and can see the EEPROM file in there. Luckily I am able to use the laptop with my left hand, while the right one is keeping the QMX left button pressed HI.

I haven't tried loading the firmware yet, as I reckon this is not normal behaviour: the assembly instructions clearly state to press the left button momentarily, not to keep it pressed while loading the firmware.

Hope it's more clear now.

Thanks in advance

72/73 de Enzo M0KTZ
 

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I had a similar issue after fixing the Q103/Q104 short and found that I had inadvertently lifted the lead of Q104 closest to to Q103 during heating to move Q103. Suggest you check Q104 closely and make sure it completely soldered. My QMX is now up and working?
Nigel,? VK6NI
 

OK, mystery solved: the issue was indeed in Q104, but the poor boy wasn't toast. One of the pins just needed a bit more solder. I could ascertain that the issue was with Q104 after having loaded the firmware ("look mum! one hand!") and verified that the buck converters were indeed working properly (PWR_HOLD was on and all the lines from the MCU to the PS boards were OK). A closer inspection revealed the tiny issue.

It boots and works properly. I had a quick look at the serial interface, but it's office time now, so shut it down and will be back to it tonight HI. At least I think I know understand the boot sequence much better than before.
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Thanks everyone for the help and suggestions: they were most useful.

72/73 de Enzo M0KTZ
 

Just to confirm that the rig works like a charm. Have had a few QSOs already on 80m-40m-30m. Re-stating the obvious here: it's a fantastic little rig. It gives 4W solid on all bands with 12V (slightly less on 20m, hardly noticeable), super-hot RX, good keyer, all details to high standards, as expected from Hans HI.? Thumbs up.

Will probably try the super-weird transformer on the next one. Wondering whether anybody has started experimenting with higher bands already ;-)

72/73 de Enzo M0KTZ
 

I found that the two tabs of Q104 nearest the edge of board weren’t soldered – there was continuity when I tested with multimeter, but when I touched Q104 with screwdriver it rotated on inside tab. ?Presumably pressure from probes made a circuit and showed false continuity.? Now soldered and fixed. ?I resoldered the third (inside) tab of Q104 just to be sure.

I have the squares on the screen and not able to switch off, so I loaded the firmware using the ‘force load’ procedure.

I’ve followed the extensive advice on various threads, including Hans’ very helpful descriptions of the start-up process.? And quadruple checked for solder shorts etc on board, as well as continuity testing where I can. ?It’s not a display problem, as I can measure correct voltage from the front pins.

VDD, VCC and +12 show correct voltage measured on psu pin outs on bottom of board (I’m using a 7V supply, so +12 reads +7).? PWR ON is ground while switch held and then shows 1v when switch released. ?PWR HLD is constant 3.3V.

However, LIN REG EN stays at 3.3V and doesn’t go to 0, so CPU isn’t booting and therefore presumably causing the display problem and inability to switch off.

However, I can’t yet find a reason why.? I welcome any insights!!

Altho the rig isn’t yet working, I’ve certainly learnt a lot and I’d like to thank everyone who has contributed to the various threads on this start-up issue, including Hans who seems to have the ability to multi-multi-task!!? The diagram and values of the PSU pin outs posted by Colin K6JTH was invaluable -thanks Colin!

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