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Alpha Clock Five Blue Edition 5th LED Group Won't Light

I just assembled the Alpha Clock Five Blue Edition and the entire 5th LED group isn't lighting up. The rest of the LEDs work flawlessly. What can I check? I will double check the solder joints again, but I'm fairly certain they are fine. Could it just be a broken LED?


  • Try to (gently) rock out one or two of the LED modules-- if you can swap two of them, that should be able to confirm for you whether it's the LED module or the board.

    Since all of the segments are out, it would certainly suggest that it's not the LED module or soldering at the joints there, but rather an issue with the "common" signal going to the whole LED block.

    Make sure that your chips are fully seated. Check the soldering at the resistor packs, at U5, and at the transistors. Make sure that you don't have one of those transistors backwards, too. If everything looks good there, double check the soldering at U1 and your LED socket.

  • Swapped out LED. It's not broken. Now I'm going back and double checking the soldering. It doesn't look like any of the transistors are backwards, and the resistor packs are in the proper configuration as well.

  • In our experience, 8 out of 10 times, something like this is caused by a poor solder joint. If you can't find the problem in the first pass, please let us know and we can make some additional suggestions.

  • I found the problem! It was one of the solder joints on one of the resistor packs. I must have overlooked it because it was totally unsoldered. Just a bare pin sticking through the hole! Thanks for your help again!

  • Great; glad to hear it!

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