Hi I ordered online a voltage meter and got this tiny cute little fast refreshing pretty darn precise reliable meter. HOWEVER I am missing on all four digits the left lower vertical light piece. What could be causing this? the solder joins look okay so where exactly must I check to fix this myself?
Best Answer
One of the display segment lines (with a resistor) is broken somewhere between the die and the display insides. Chances are its crummy soldering by the manufacturer, but it could be a bad chip or display or resistor. That will cause segment E to be off on all digits.
Look at the soldering of the lines on either side of the array of 8 resistors and to the resistors themselves. In particular look at the one highlighted below:
Edit: I've shown the possible places (blue arrows) where a solder joint could be bad, based on the usual pinout for such an LED display, but I think I see the problem- there appears to be a cut in the trace (circled in red). The solder joints don't look obviously bad. If it is a break (look at it under a microscope or magnifier) you can scrape the solder mask off gently with a knife and bridge the gap with a bit of very thin wire and solder.