I picked up this 1979 Stern Meteor pinball machine in mostly working order. Some of the displays were flaky. They worked at the guy’s house but must have been barely hanging on. One was flickering and one had some burn.
After moving it into the house, the flickering one stopped working altogether and the other one developed a situation where the bottom segment was out on all digits.
I got that one working again with some parts from Big Daddy (Bally Display Driver Kit) and a bit of sleuthing thanks to PinWiki.
WARNING: These displays run on LETHAL high voltage ( 170VDC). Do not touch with the power on!
5.12.2.5 One display is missing the same segments on all the digits
5.12.2.5 One display is missing the same segments on all the digits : Each display has it’s own decoder chip, which takes four inputs from the MPU and outputs seven signals to light the seven segments of a digit. If you’re having problems with one or more segments on all the digits, then it’s either the segment driver transistor or the decoder itself. I’m sure there’s a way to test the transistor but I just go ahead and install a new one. If that doesn’t fix it, then replacing the decoder will. I’ve not had a segment problem that was not fixed by replacing both segment drivers and decoders (other than MPU problems). Be sure to orient the transistor and/or IC in the proper position. You’ll notice a flat side on the transistor and a small notch on one end of the decoder IC. Be sure they line up just like the one you removed, and that the wires of the transistor go into the same holes that the old one came out of. Also, if you’re replacing the IC, use a socket, so it’ll be easier to replace it next time. Here’s a handy chart that shows which segment driver transistor drives which segment, and another diagram of how the segments are labeled. Just find the segment that’s giving you trouble on the chart, then look up it’s corresponding driver transistor. Then find this transistor on the circuit board and replace it.
https://www.pinwiki.com/wiki/index.php?title=Bally/Stern#Repairing_Bally.2FStern_Displays
The Big Daddy kit had two different transistors. Neither matched the numbers on the original. I choose one, installed and the bottom segments stayed lit all the time! Took it out and tried the other one and it worked! “a42b331” was the one that worked for me.
