On 27 Jan 2021, at 12:26, M0JHS <graham@...> wrote:

Thank you Dan, I did kick myself when I spotted my soldering mistake!

That's just it, I'm fairly newly qualified as you might guess by my call sign.
QCX+ is the first proper radio kit I've built (I've designed and built other microprocessor stuff in the past), uBitx is pretty much assembled.
I looked on here for an FAQ or previous posts that went further than Hans' excellent manual, but drew a blank, hence my question.

So, if bad soldering of enamelled wires is a problem, the big question is how you go about addressing this?
Clearly a long post pointing out the lack of experience of those new (M6, M7s) hasn't solved it, neither is this post as it soon gets buried.

When I'm next soldering enamelled wire I'm going to deliberately make a poor solder joint, photograph it and make a file/post to show the difference between a poor and well made enamelled Cu wire join. Not sure how to make the file/post sticky but a resource like this would go a long way to a) helping other (new) amateurs b) reduce the amount of questions like I posted c) reduce the exasperation of more experienced amateurs replying to newbie questions.

Thank you to all who offered advice and helped my learning.
73
Graham
M0JHS

Graham,
I know Hans likes this method, but if you try this you will never go back...

At the risk of offending someone (which I'm really not trying to do) this is a design error on multiple levels. Stereo plugs are not designed to be power connectors and it was misguided to use them as such. There is also an accepted standard for hot plugging stereo connectors that doing so will not destroy the equipment. This design violates both standards.

Power connectors are designed to prevent short circuits. They are polarized and use separate pins for each voltage and ground. The stereo plug does not fit this requirement. The assembly manual even alludes to it by mentioning the change from the QCX+ boards to try and avoid this problem. In reality, it can never be avoided with a single pin design (and now there is the problem of incompatible connections to the PA kits).

User interfaces have standards, both implied and explicit. This design violates the implicit standard for stereo phone plugs. All our electronic lives we plug and unplug stereo jacks with impunity. Stereos, phones, TVs, etc.  never blow up when you plug in/out headphones or speakers. At worst, they make a loud annoying click. So we are quite thoroughly trained that stereo plugs are safe to plug/unplug under power. Even with a warning label, it's still a problem because that poor label is trying to fight years of training and reinforcement of the user/operator.

The real answer is to fix the design by changing to another connector type. The change can be retro-fitted to some extent by kit builders, though at the cost of some convenience. For example, cutting the +5v trace to the PTT jack combined with Gregg's move to supply GPS power from an external power supply will totally fix the issue. Or, the power trace can be cut and another connector with 2 pins that don't short each other when plugged/unplugged (preferably polarized)  can be used to carry the power separately from the signals.

I realize that QRP Labs is not  a huge consumer products manufacturer and that its target audience is people with a certain level of technical skill so many design processes and methodologies that the big companies use don't apply, but in this case connector selection standards should have been followed. With any luck, the next PCB rev will fix this.

73,
Laszlo

On 27 Jan 2021, at 08:25, Alan G4ZFQ <alan4alan@...> wrote:

Who is the target, Howard?

I'd guess anyone who might read it before they actually build a kit.
Bad soldering of enamelled wires and not re-soldering because "they all look good" is a very common problem.

73 Alan G4ZFQ