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QMX - no power

Jeff All Messages By This Member #120432 Hi All. After 8+ months, and 2500+ QSOs, a sad day here today as my QMX will not power up.? Pressing the left encoder doesn't turn the?rig on. I have taken it apart, and not seeing anything obvious, so I went looking for a troubleshooting guide.? Does one exist? Has anybody else had issues with a QMX that no longer powers up? Thanks -- Jeff Hetherington VE3CW / VA3JFF
Evan Hand All Messages By This Member #120435 Hi Jeff, Here is the QRP-Labs guide: 73 Evan AC9TU
Jeff All Messages By This Member #120438 Thanks Evan.? I see the issue now - I’ve had a failure in the 5V converter board.? time to go to the parts page and get some replacements.? Thanks Jeff
Evan Hand All Messages By This Member #120441 Jeff, I would do one test before ordering the power supply replacements. Verify that you do not have a short to ground on the 3.3-volt and 5-volt rails with the converters removed. If there is a short on the mainboard, replacing the converters will not fix it; it will just damage the new converters. 73 Evan AC9TU
Jeff All Messages By This Member #120443 I don’t see any shorts but will test further this weekend. ?I have used the QMX for the past 8 months and over 2500 QSOs so it will be a missing piece of my portable kit, and I’ll need to figure out how to get it back up and running now that we’ve finally gotten out of the winter.? thanks?
Steven Dick, K1RF All Messages By This Member #120481 I posted on this before. Do you have a Rev 1 QMX? It has a low power 1/2 watt zener diode rather than the 5 watt diode on rev 2 or 3.? if the shorted D108 is your problem, indicted by a low resistance in both directions (not a dead short but perhaps 20-30 ohms or so)? it might be easier for you to order a? set of regulator boards on the QRP labs site. The 5V regulator as spare parts or on on the Rev2 and Rev 3 board has a very robust higher power 5 watt zener diode.? The other regulator board is good backup if you purchase both. You can buy individual boards or the pair of boards for the same price.? That might be easier than replacing that tiny diode in a cramped place.? I wouldn't recommend it because of the difficulty in soldering it and no room for a higher power 5 watt diode, and the same problem could happen again in the future.? If you want to buy one, that diode is a?5.6V 500mW zener diode in an SOD-123 package.? I pm's Hans on this subject and he recommended? a workable diode to purchase is?Digikey part number?BZT52C5V6-TPMSCT-ND which is diode type?BZT52C5V6-TP.? -Steve K1RF toggle quoted message Show quoted text ------ Original Message ------ From "Jeff" <jeff.ve3cw@...> To [email protected] Date 4/5/2024 1:18:13 PM Subject Re: [QRPLabs] QMX - no power Thanks Evan.? I see the issue now - I’ve had a failure in the 5V converter board.? time to go to the parts page and get some replacements.? Thanks Jeff

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