It would be lovely to make a drop in LED replacement, but unfortunately, the logic control circuitry is all high voltage stuff, unlike the Bally displays, where all the logic control circuitry is low voltage stuff with the high voltage only going to the display glass tube.
There are 6 IC's on the controller board that are powered by, and outputting at, 100 volts or -100 (minus) volts.
This is why the led replacements have a brand new controller board, using low voltage.
There is a (theoretical) cheaper alternative, and that is to remove the +100V and -100v feeds to the board, and then connect the +100v and the -100v lines to +5v.
4 of the high voltage IC's are designed to run at supply voltages between 5v and 100v (UDN6184), so should still work ok.
The 2 IC's powered by -100 volts (UDN7180) would need to be removed and replaced with a 5v inverting line driver Ics - there are plenty of those that should work.
The output to the displays is very simple. +voltage to anode (need common anode 7 segment displays) and then the segments are individually controlled by dropping their line to 0 volts.
