Today's head scratcher is Take Five's credit display. It loses a segment when it heats up and it also has one segment that's always a bit dim.
The resistors measure fine, but I'm not seeing the operating voltage coming through this one segment's LED. I check them with a thermal camera but nothing seems to heat up out of ordinarily. I hope it's not the 7-segment itself as this model is getting rare.
Then I make an accidental discovery, the issue can be triggered by tapping the board, but it's not a cold joint. I end up replacing the whole 7-segment, which as an added bonus took care of the dim segment too. Wasn't that mysterious fix today.
This board is pretty simple, it has a shift register, two 7447's to run the 7-segments and then couple of passive components. The score displays have similar design, just more displays to control.
#pinball #pinrepair #electronics #retrotech