Bally stern test rig

[BallyWilliams suck]

Does anyone have any information about the Bally / stern test rigs from the late 70's?

Each of mine appears to differ somewhat, although they are clearly both based on the same control pcb (as-2893-1)

I've uploaded a picture of the pcb inside my Bally test rig. U24 isn't populated (and never has been?) but the stern version clearly has these bits populated.
(Second pic)

Google appears to have no information at all.

Can anyone help? Manual, schematics, etc?

 

[BallyWilliams suck]

Bally version

 

[BallyWilliams suck]

Stern version

 

[BallyWilliams suck]

Stern rig

 

[BallyWilliams suck]

Bally rig