Re: Did I fry my QMX SMPS or is it likely worse?
#qmx
Easy way is to check for short across the big yellow tantalum capacitor on each board. Test in both directions with a multimeter on a low ohms scale.? It should read open in at least one direction.? If it fails this test the zener diode is toast.
------ Original Message ------
Date 2/27/2024 5:50:54 PM
Subject Re: [QRPLabs] Did I fry my QMX SMPS or is it likely worse? #qmx
Thanks for the reply! Could you guide me on where to test?
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Re: QMX HIGH BAND NO RF OUT AFTER ANOTHER 10 hour WSPR TRANSMISSION
good morning Michael, yesterday I replaced the 4 bs170s and the problem remained the same, the strange thing is that I made many QSOs in cw with 5/6W on the bands here in my area, then I tried to transmit in wspr on the 10 mt and after 10 hours of transmission the qmx died, no more rf came out, the problem is that I bought it already built from QRPLAB, I'm unlucky, now I have two non-working QMXs and I can't repair it because it's not clear what it is success, �250 wasted.? I hope you can solve your problem.? Good luck.? 73
Giuseppe iu8eun
OK so you have a different problem then I do.
My QMX just stops transmiting WSPR after 10 hours or so even though the display still shows the transmission when the time comes.
I have noticed this all along (with other firmware revisions).
If I turn the QMX off and on it will work fine again most likely for 10 hours in the WSPR mode.
Michael N2ZDB
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Did you only apply power, or did you turn it on? If the former, you might be OK. If the latter, what happened?
I wouldn't think just applying 26 volts would damage the supplies, if they were off... If you apply current limited (250mA) 7 volts, what happens? :-) Current before turn-on should be quite low and the receive current listed in the manual, after turn on. Higher current probably indicates damage someplace.
(If damage was done, it probably won't be made much worse by the?gentle prodding above, or so I think...)
Good Luck!
73, Paul -- AI7JR
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Re: Did I fry my QMX SMPS or is it likely worse?
#qmx
K3KDW,
No, I would not order the new boards.? I believe that you have damaged the 5 volt and 3.3 volt devices.? You could check with Jeff Moore W1NC on QRZ.com for his email address.? He can diagnose and repair the QMX and has had great reviews in this group.
73
Evan
AC9TU
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Re: Did I fry my QMX SMPS or is it likely worse?
#qmx
That pdf is gold. So I only have a few ohms between vcc and gnd and vdd and gnd. I don’t know what normal measurements are though. Is it worth ordering a fresh set of SMPS boards?
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Re: QMX Display Brightness
Thanks Hans,
I'd tried tracking through the labyrinth of documentation about this but it's very difficult without spending a shed load of time deciphering it.? It it's not obvious it isn't worth it.? I'll just change the resistor.
Thanks again,
Chris, G5CTH
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Re: Did I fry my QMX SMPS or is it likely worse?
#qmx
K3KDW,
You want to measure the resistance on the bottom of the mainboard with the power supplies removed.? Attached is a PDF with the pin locations.
73
Evan
AC9TU
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Re: Did I fry my QMX SMPS or is it likely worse?
#qmx
Thanks for the reply! Could you guide me on where to test?
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Same here.
I ended up finding a seller on Amazon a few weeks ago and grabbed one.
Todd K4MSW
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Re: Hyelec PS-28A 0-15 VDC, 0-2ADC power supply plus a simple crowbar circuit for protecting all of my QRP rigs
I agree, my Motorola Service Monitor has a TO-3 zener diode on a huge heat sink protecting its 5 volt supply. Gotta love brute force.
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Re: Did I fry my QMX SMPS or is it likely worse?
#qmx
Unplug the SMPS boards and check the resistance to ground of both the 3v3 and 5v0 supply rails on the main board. If the 3 volt rail shows only a few ohms or less there is a high probability that the MCU is toast.
JZ KJ4A?
I accidentally fed 26v to my QMX. That's what I get for keeping too many running projects laying around, especially when they require wildly different voltages but the same plug format. Next time I'll tag the only correct supply.
Am I probably safe once the SMPS boards are replaced or is there a good chance for more damage?
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Did I fry my QMX SMPS or is it likely worse?
#qmx
I accidentally fed 26v to my QMX. That's what I get for keeping too many running projects laying around, especially when they require wildly different voltages but the same plug format. Next time I'll tag the only correct supply.
Am I probably safe once the SMPS boards are replaced or is there a good chance for more damage?
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Re: #key #qmx QMX Straight Key Mode incorrect
#key
#qmx
First time installment of a firmware on a new QMX (no EEPROM file) will not initalize all menu settings correctly. In the menu the keyer setting defaults to straight and tip.
Change it to to e.g. iambic a and ring and leave the menu. Then reenter the menu and revert the keyer setting back to straight and tip.
HTH Gottfried
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If you're interested in ordering the?VIFLY ShortSaver you might as well order them directly from China via AliExpress and save some money. I ordered some from?VIFLY Drone thinking that I was helping a small business and would get them in a timely manner. Well after a week I finally got an order confirmation and that they were being shipped from China. A couple more weeks have passed and I still haven't gotten them. They have at least gotten through customs!
Roy
WA0YMH?
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How about just using an attenuator with a bypass for receiving? QRPGuys have one for 25 dollars or so.?
Don Meyerhoff WA2SWX?
Easiest way is to remove 2x BS170 and run on one BS170. Then you will in QRPp range.
--
?
73, Barb, WB2CBA
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Re: #qmx filter testing and adjustment
#qmx
Oh, yes, that was a nice trick.? I figured out the problem with 15m is that the cutoff frequency is too low, and 21.074 MHz is actually more than 3dB down.? I did the transmitter test at 19MHz, well inside the passband, and got 4W.? So I need to tweak the toroid to push the cutoff frequency up.? The same might also be true, to a lesser extent, on 12m and 10m.
Eric
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I accidentally plugged in a 26v supply from another ongoing project. Do you suspect I'm ok after replacing the SMPS boards or is this disaster likely more serious?
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Re: QMX: C516 - C525 swapped value
#qmx
Thank you very much for the information.
Now I can proceed with the assembly with peace of mind.
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Re: #qmx wrong inductances for LPF?
#qmx
On Tue, Feb 27, 2024 at 08:20 AM, @Ludwig_DH8WN wrote:
Please be aware of the different stray capacitance and the capacity of the connected QDX circuits. And use a rf suitable board!!!
My final result of my whole testing was: Following the manual brings good results or at least a good start point to tweak the filters.
Thank you for your thoughts and clarifications! The more I play in Elsie with LPF simulations, the more I agree that following the manual will be a good start. It seems in the QDX HB, the 15/17m LPF is the most sensitive to the inductance values. The others are more...robust. Especially as far as reflected power to the PA. And there are more downsides to using less turns on the 15/17 than the recommended number of turns, even if inductance is higher than spec'd/calculated. So I will follow the manual pretty closely, maybe doing 20T instead of 21 on L2, but that's the only change.? -Nate? N8BTR
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Re: QMX: C516 - C525 swapped value
#qmx
On 27/02/2024 15:45, jh4vaj wrote: t appears that the values of C516 and C525 are swapped between the schematic and the manual. "The current assembly manual is correct: C525 is 270pF and C516 is 180pF. " Be careful, simulations must account for stray capacitances. 73 Alan G4ZFQ
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Paul - AI7JR
Tom - AJ8X