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 Larson Scanner: One LED won't come on??
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By: Anonymous: STAN () on Thursday, October 27 2011 @ 08:27 AM PDT (Read 1182 times)  
Anonymous: STAN

I have to admit, this was my first electronics-chip-soldering project ever! The 'electronics for dummies' instructions were great and overall, it wasn't so hard! However, I do have one LED that doesn't come on- D0. I swapped out the spare LED and still no dice. (I did check to make sure the short lead goes into the flat side as well)

Thoughts on what else i can do to troubleshoot? It's working great with the other 8 LEDS! Thanks.

By: Windell (offline) on Thursday, October 27 2011 @ 11:37 AM PDT  

It's a very simple circuit, and there's really not that much that can go wrong. For that LED to light, the electrical connections have to be made from both sides of the LED to where those signals come from. On one side, the electrical connection goes to the resistor, through that resistor to the other side, and then to the chip. Check each part of that: trace the wiring on the circuit board to the resistor, and check the soldering at both sides. Then trace the other side to the chip, and check the soldering at that pin of the chip.

If everything is good there, it's possible that you've torn one of the printed wires on the circuit board. The most likely location for this is right at the LED, so check both of those to see if there might be a problem. If so, you can add a wire by hand (clipped resistor or LED lead) to connect the wire where it needs to go.

Windell H. Oskay

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