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Further help needed debugging

I have made 8 panels of the interactive LED display. Windell helped me to debug three of them and I have 7 running perfectly. However one is still not working. I had several challenges when I set it up initially. I had accidentally used some of my 5.1 kilo ohm resistors in practice (hadn't soldered in almost 30 years) so I was one short (R116). I desoldered one from my practice board and resoldered it into R116. I also had had a problem putting the diode in at D2. The hole was plugged when I went to put the diode in. It was a struggle to get it in and I only succeeded by leaving the soldering gun and melting what must have been solder plugging the hole and forcing the diode in. The pattern I have when it has power is that every second light is on to stay. The photoresistors have no effect. Does anyone have any idea what I can do? I got new 5.1 kilo ohm resistors and replaced that one that was sketchy. I have gone over the whole panel. I am wondering if it is the diode that is causing the issue. They are put in the right way, btw.


  • If diode D2 is not installed correctly, or if it has a bad connection, that would indeed cause this symptom.  Check to see if there's a bad solder joint there, or if perhaps a trace on the board has been torn.
  • edited August 2012
    OK. I may try to buy another one from EMS, if I can't resolve it by fixing the solder joint. Thanks again.

    I will go check it (again) now.
  • It's very likely to be repairable if you can identify the trouble spot; don't give up yet! :)
  • edited August 2012
    Wow, fixed in record time! I now have eight functioning panels. I do not know how to thank you.

    I rechecked the solder joints and one seemed sketchy, so I redid it. No change. While the panel was powered on, I looked closely at the front of the panel. Most of my debugging has focused on the back. I saw a little piece of metal sticking up that must have been pushed out when I struggled to get the diode through the blocked hole. Thinking the piece of metal should be removed, I used a mini screwdriver to take it of. When that piece of metal contacted my screwdriver which as also touching the diode's wire, the lights changed and started blinking in the correct pattern. So I soldered that piece of metal on top of the panel and it works perfectly. I can not believe it is finally working.

    You were dead on in that last post. And I rarely give up.

    So thanks a million.
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