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Hi all. After slooowly assembling my QMX main board, I finally completed mounting all the electrical components. I don't any issue with the potential buck regulator short issue. I measured all tthe LPF and BPF filter caps for accuracy and they were all fine.? I also measured all the toroid inductors as I wound them.? I did find that I sometimes had to remove a turn or two, measuring their value at the frequency it was designed for. This is overkill, but we'll see how the power looks on each band.? I used my Rig Expert AAA-55 zoom for these measurements using the "all parameters" mode. The numbers agreed closely with my cheap LC meter (eBay LC100A or LC200A - I have both).? The Knipex tool worked great on the heavier .33mm wire.? For all the toroids, I stripped the end of the wire before starting the wind so they wouldn't need stripping after the wind.? On L401, when I got to the 19th turn, I used the Knipex tool to strip the wire length needed for the loop, then made the loop.? This greatly eased trying to strip the wire in the loop after completing the wind.

? I would make the following simple suggestions.? If I sound like Captain Obvious, please bear with me.? ?First, it is a good idea to get a PCB holder of some sort if you don't have one, like the Vellman VTHH6-VP for about $16 on Amazon.? I've had one for years and use it a lot.? Second, if you don't have one, get a close cutting wire cutter such as a??Xcelite Weller 170MN for less than $12. It gets you as close as possible to the PCB when cutting off the excess wires. Use this tool only for cutting small wires or component leads and it will last you for a long time.? ?Sure you can get away with any old side-cutter, but it will not get as close to the type listed.? If you don't have good optical inspection tools, invest at least in a 10X jeweler's or watchmaker's loupe which go for about $7.. You can splurge on a set of 5 with different magnifications for about $15.? Inspect as you go along. Don't wait for the end.

But here's the best inspection tool of all, which you likely already have.? Take a photo of the top and bottom of the PCB with your smartphone with highest size available.? You can them look very carefully at the photo with app that comes with your operating system like Paint in the Windows OS. Zoom in, and you can get great quality, high magnification with this tool you already have. Use good lighting when you take the photo and avoid blocking the light with your body.? Perhaps a friend or your better half can shine a flashlight on it if necessary.? I like to add little red circles around suspect joints in the photo to mark on the photo where I have to look and possibly touch up.? The top of the main board had no issues.? The bottom or hand-soldering side of the board had about 8 potential issues, including a small solder ball between two adjacent pins of the processor, solder bridges, and unsoldered pins.? The USB connector had an unsoldered pin in the upper left corner.? ?Also inspect with your naked eyes, which might pick up something when light hits it differently that when the photo was taken.

Inspect, inspect, and inspect!? Don't gloss over or rush this important step (I know I know you are anxious to finish it and watch the grand powerup!)? But trust me, a pound of careful inspection is worth 100 pounds of letting the smoke out.? Good luck with your builds.

-Steve K1RF

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John,
Your explanation of QDX L14 makes sense. It doesn't seem to be a serious problem for semiconductor failures tho. More of an issue for spectrum 'dirtiness'. The diode would take care of both concerns.?

I wonder why it could not be taken care of in the QDX firmware, as it has been with the QMX. There doesn't seem to be the memory and processing constraints of the QCX, even though it doesn't have the capacity of the QMX processor. ?
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73, Dan? NM3A