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Dear QRP Labs Community,

I’m guessing you cooked the SMPSs on kit #1 - hopefully they acted as “fuses” and prevented damage from occurring elsewhere in the rig.

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I believe you can order replacement SMPSs from QRP-Labs.

W6CSN,

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Thank you so much for taking a crack at diagnosing the issue with both boards—I really appreciate it!

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To clarify exactly what happened:

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Kit #1 was originally configured for 12V, but I accidentally fed it 30V, and it stopped powering on.

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I built Kit #2, configured for 9V, and attempted to use the SMPS boards from Kit #1. It did power on, but nothing displayed on the screen. At this point, I figured the SMPS boards from Kit #1 were fried.

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To see if just replacing the SMPS boards on Kit #1 could revive it, I then swapped in the SMPS boards from Kit #2 into Kit #1, but it didn’t power on at all.

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When I returned the SMPS boards to Kit #2, unfortunately, it no longer powered on either.(made sure not to get them confused in case anyone is wondering) Now, neither kit shows any power consumption, except when I press and hold the left rotary button—it briefly shows some power draw, but once I let go, it's dead again. Both kits behave the same way now.

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I’m really hoping it’s just the SMPS boards, but I have a feeling it might be more than that at this point. Any additional thoughts or advice would be a huge help.

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Thanks again for your time and input!

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73,

Eddie W2FTL?

Hello Eddie,

please ready this document from QRP Labs Wiki.

73 Ludwig

Fault finding by substitution is a risky process in power stages

Hi Ludwig,

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Thanks again for the link! I did take a look at the document and followed the steps for troubleshooting the SMPS boards using the terminal. Unfortunately, both of my assembled QMX boards only consume power when I press the left encoder button, but they immediately stop drawing any power as soon as I let go.

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I’ve closely inspected both boards for any signs of physical damage, like burned components, but everything looks clean. I’m concerned that the SMPS boards from Kit #1 were damaged when I accidentally applied 30V, and when I placed them into Kit #2 (which was working fine), they might have sent too much voltage to the processor, potentially killing it. It’s really disheartening, as now I might have two damaged kits—or, at the very least, a lot of spare parts.

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If you have any other suggestions, I’d really appreciate them!

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73,

Eddie W2FTL

Hi Bruce,

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I certainly agree with you now! I’ve definitely learned my lesson the hard way. I just hope no one else tries to be a hero and attempts to save their boards the way I did—it could save them a lot of disappointment.

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Thanks for the insight!

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73,

Eddie W2FTL

Hello Eddie

following the link in my former post you will find information how to test the SMPS boards and the mainboard.

73 Ludwig

Hello Eddie.

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Ludwig's suggestion to look at the WIKI doc is spot on.

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I'd check the ohms continuity between ground and each of the VCC and VDD rails first. Remove the SMPS boards boards before doing this and do not apply power or have any other cables or keys attached.

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If too low or especially if showing close to shorts then one or more components on the? main PCB have failed. Tracking those down is difficult. There are several threads where advanced operators have tracked down one or more failed components. Hard and amazing analysis and rework.

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Or, you could contact Jeff Moore for his excellent repair service. Query him at QRZ for his private email address. He revived my QMX+ Rev 1 quickly. I subsequently blew up that one while probing poorly with temperature sensors. The standalone SMPS board checks led to finding one was toast and that one of the rails was shorted on the Main PCB?

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I opted to purchase a 2nd QMX+, a Rev 2, assembled it very carefully and I am back on the air. Now have a component donor main PCB board for future fumbles. :)

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73 GREG KI4NVX?

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Eddie,

?I agree that repairing the SMPSs is probably not a good idea. My first QMX (rev 1) kit failed with an exploding tantalum cap on the 5V SMPS. Initial tests on the repaired unit looked good and the unit powered up fine, but a few minutes later IC401 failed and the radio shut down. I was warned to get new SMPSs, which were just coming out on QRP Labs' site.?

Good thing I listened, as later tests showed serious problems with my repaired boards. Fortunately the IC401 was the only casualty from the initial use of my repaired SMPSs.?

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73, Dan? NM3A