View Full Version : Repairing Bally 6 digit displays

26th June 2008, 07:47 PM
The 6 digit displays on my Bally Future Spa were all doing odd things. Some had bad ghosting and flickering while others counted in weird ways!

Anyway, if yours have some whole digits not working, replace the six 100K resistors. They're R1, R3, R5, R7, R9 & R11 and are marked very clearly on the board in two groups of three. I replaced them with 100K 0.6W metal film types. Almost all of them measured in the 110K - 1M range with a couple completely open circuit!

On the other hand, if the digits all work but the numbers don't make sense or seem to count "out of order", replace the MC14543 IC on that display board. That IC on each of my boards had corroded legs. Replacements were very cheap.

I ended up replacing the IC and the six resistors on all five display boards as well as resoldering any suspect (cracked) joints. That seems to have sorted all of the issues with the displays. Given that they are about 30 years old I'd suggest that there's a lot of machines out there that will have the same faults.

I hope this helps someone and saves them from blindly buying new boards when there's very little wrong with the old ones. Long live pinballs! :)

26th June 2008, 08:17 PM
David - You have pretty much covered the basic repairs needed on the 6 Digit displays. The 100K Ohm Digit resistors should be replaced with 1/2 Watt if possible. Header pins are the main source of problems on these boards.

After you have done your Displays, head up to the Solenoid Driver and check your voltage at TP2 and TP4 (with respect to GND). These should not be both 240 VDC.. If they are, see if you can adjust the pot so TP2 read 175DC. This will prolong the life of your repaired displays ! ie TP4 = 240VDC, TP2 = 175VDC

26th June 2008, 09:27 PM
Yeah, the 180V display supply was one of the first things I checked when I got the machine. The pot is a little twitchy so I'll replace it soon.

I'm sure the new 0.6W metal film resistors will outlast the machine! It's info like this that will keep those pins going!

Pinball Warehouse
26th June 2008, 10:30 PM
Hi Dave, I have over 100 old bally displays here needing someone to repair them, do you want some practice.

Have you tried replacing the actual glass display unit yet, I have a shit of these to do also.

Not enough hours in a day anymore.

27th June 2008, 06:53 AM
What, you wanna swap some repairs for a pinball machine?
I'll drop over and we'll go from there! :lol

27th June 2008, 07:39 PM
Just an update: I forgot to mention that there's (at least) a couple of different versions of the Bally 6 digit display board. The 100K resistors on the other (newer?) version are not in two groups of three. They're not in groups, but all in the middle row of components and still labelled R1, R3, R5, R7, R9 & R11.

Also, the IC on some of these boards is marked with some oddball custom number, but it's still a MC14543 type. If you still have missing digits after replacing the resistors, Tony tells me that the column transistors (MPSA42 ?) do clap out sometimes.