U3S + 12V = Fried U3S

Well I have now printed a label for the power connector on the U3S enclosure saying 5V, but it’s a little too late for an assortment of components that inadvertently were subjected to not just 12V but closer to 14V! Yikes.

From consulting the FAQ on the QRP-Labs site at https://www.qrp-labs.com/faq.html I have learnt that I’m am by no means the first to commit this blunder! In fact – as the FAQ on this topic reveals – so many have trod this well-worn path that there’s a pretty good understanding of what needs to be repaired and what probably survived the onslaught of unwanted volts.

Net result as I understand it is:

  • the main processor, a 28 DIP ATmega328 chip is definitely fried! I do have the option to program a blank one or order one already programmed from QRP-Labs.
  • The LCD display has been zapped.
  • The relay on the main Ultimate 3S board has most likely been burnt out as well by the higher voltage.
  • It’s supposed to be unlikely that the Si5351A Synth Module has been damaged.
  • On the QLG1 GPS unit it’s probable that the 74ACT08 level converter chip has been destroyed by the high voltage because of the way the LED indicators are behaving when power is applied. Yellow is not pulsing once a second as it should…

This is such an unrare event that QRP Labs have created a product especially for people like me – the QCU QRP labs control unit which components most likely to need replacement after applying the wrong voltage! It includes the 16 x 2 LCD module, 20MHz crystal, BS170 transistor, buttons, resistors, capacitors, hardware and all connectors (4-way sockets, 10-way sockets, 16-way plug/socket for LCD) that are used in the Ultimate 3S kit.






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