If you own an old Bally or Stern pinball, then having working displays is a must...
Every now and then, one of the digits (numbers) on a display will disappear completely. Thankfully, it is usually a really easy fix...
Most of the time, it is a resistor that has gone open circuit. There are 6 (or 7 in the case of a 7 digit display) 100k ohm, 1/4 Watt resistors that are part of the power circuit for each digit.
These resistors are getting quite old now, so they should be replaced to ensure the display continues to work.
Once they are any more than 10% out of spec (110k ohm or above), they are on their way to failure...
When replacing these resistors, use 100k ohm, 1/2 Watt resistors. Or better yet, 100k ohm, 1 Watt Metal film resistors. Metal Film resistors are often around half the physical size of a standard carbon film resistor, so they can handle more heat in a smaller package.
The resistors marked above are as follows (6 Digit Display):
R1 - 1's Digit
R3 - 10's Digit
R5 - 100's Digit
R7 - 1000's Digit
R9 - 10,000's Digit
R11 - 100,000's Digit
On the 7 Digit Display,
R56 is used for the 1,000,000's digit - 100k ohm resistor also.
