the Bromley manual has nothing about credit settings. I have copies of the Unis ones, but they're entirely different. I should've asked if yours was the older Bromley or newer Unis one.
I strongly encourage you keep the game at 1 coin per credit and use the 7-7-15-20-40 setting. I can take a picture of the board on the one at work, it's set exactly for all of that.
something else for you to test in the meantime though, there's the spinning drum assembly. the main board runs to a small board which then has wires connecting to the tabs for the wiper pins which touch against the sliprings. the head inside the wheel with the switches that the ball rolls into has a harness that connects to each of those sliprings. pull back on each of the wiper pins and verify you get a little click sound against the rings. this way you'll know that they're making contact. if you have an intermittent contact issues you can run into problems with the ball not registering against the switches. each of the wiper pins should have a spring. the L-brackets that the wiper pin assemblies are attached to are adjustable in and out from the rings. you want these to be set as loose as possible so as to not promote grinding the wiper pins. heavily worn pins will have a round chunk missing from them, after which they should be replaced. I think they're supposed to be about 1/4" thick on the fatter end that touches the rings -- if they're worn away badly, they'll need to be replaced.
the secret to prolonging the life of the wiper pins is white lithium grease. there's a bracket that supports the 2 L-brackets in the middle; remove this from the rear door side. apply the grease liberally on each of the rings, manually turning the wheel to distribute evenly. then turn the game on and press your finger against each ring while the motor turns it. this should smear it evenly. you can add more grease manually with the power off again if you'd like. I had a machine I serviced almost a year ago that the white lithium grease was still fine, to give you an idea of how great it is (or my process for applying it

) (PROTIP: wear those plastic gloves for this)
you can get replacement wiper pins from either Suzo-Happ or Betson, at least I hope you still can. I haven't replaced any wiper pins in 4 years courtesy of that grease strategy.
another helpful tip, the 2 player and 4 player models of the game are identical. the 4 player one simply has 2 more players tacked on to the control circuit. in case you need any spare parts. the driver board is outfitted with a ton of 5 legged transistors (going off memory... that's been 5 years now) -- if any of those fail you can lose lights. and conveniently they're obsolete parts that you can't find anywhere.
the lights in the actual head assembly I think are 12V, I always put 44s in them, but it makes sense now why they burn out so much if I was using 5V lamps in there. the 12V ones are 1813s, but I encourage replacing them with LED fixtures so you don't have to worry about changing them out anymore.
I haven't had to do any heavy stuff with these in a long time so I'm going based entirely off memory. if you have any problems or questions though you can drop me a PM.