12 into 5 doesn’t go

A couple of months ago I demonstrated to myself just how 12 into 5 doesn’t go, yes I know maths (or math if you speak American).

Unfortunately for me, this was more of an electrical disaster, putting 12v into my 5v QRP Labs Ultimate 3s transmitter. The display glowed unsurprisingly bright, and then blank.

At the time I wasn’t sure why, so in true fault finding tradition I turned it off and on again, several times in fact. It then clicked, or probably more precisely popped and the damage was done.

Looking on the QRP labs help file, I found a section that dealt with “Ive put 12v on my …” I guess I’am not alone, and to be honest I really cant see why this devices wasn’t designed as a 12v native power supply and then regulated to 5v.

Part 1 involved buying a new processor, these can be purchased for a few pounds online or by speaking with Hans and buying one at one of the rallies he attends.

Here is my rather sad v3.09c with burn mark!

Part 2 in my case indicated that there was an issue with the clock. I had to re-build the Si5351A Synthesizer, again available for a few pounds. The FAQ indicates this is probably OK, but in my case it wasnt and needed replacing.

Here is the new one ready to be fitted. It just needed the header pins, but I found this really difficult as my eyes dont seem to focus on anything close these days.

Once this was installed it sprang back into life, and is currently purring away at 200 mW on 7 MHz. I have been told on occasions the display can be damaged, but despite my best efforts this survived.


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  1. Really Dave?? You on 200milliwatts?? Its gobsmacked that I am!!

    Whats happened to the other 399.8watts??
    Where are they??
    What have you done with them??
    Dont you find that 200 milliwatts are a little lonely??

    1. Yes I have embraced QRP its the future. I have decided to save my watts for field days, putting them in a watt bank and making a withdrawal in the summer. Peace TAZ

  2. It’s re-assuring that the repair is reasonably straightforward. No PA then ? 🙂

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