I've been working on a Bally 5500 and have most everything sorted out. It does have a working bv however when I insert a bill it will turn that into quarters rather than go to credits.
I have tried changing option 11 in the 11d menu but it is set up 0. 1 is the option to allow credit vs coin. When I try to change the number the readout reads 'err'.
I have also tried changing option 27 to 2 which should allow the player to press the cash out button with no credits to choose between cash and credits.
The Cash out button does toggle a '0' in the credits window indicating the cash out button is registering and usually if the 0 is present, the machine will run in credit mode. Coincidentally the light for cash out doesn't light. The bulb checks out good
I've also checked the lock out settings of 54,56 and 51 which all have values of 1000 or 1001 so it's not those settings either.
What am I missing? Could it be the mains? Picture of them is attached.