Not sure what you mean by "wont take a credit". Have you tried setting the Credit unit stepper to 2 or 3 and then pressing the reset button?

Pinball (resized).png

Here's the startup sequence from the manual. If you'd like more detail from me, I'll need to see a high quality scan of the schematic from e.g. Staples ($2) or Kinkos ($6) because the schematic on IPDB is broken into multiple pages, making it too hard to read.

Pinball (resized).pngPinball (resized).png

Does the score motor complete a 180° cycle if you start to rotate one of the cams?

Is the fuse and fuseholder for the 50 VAC circuit good? Those fuseholders are pretty crappy and should be replaced.. But, if the Lock Relay is energized, we know you have 50 volts. If you don't know what I mean by score motor, Just remove the glass an put a ball in the kick out hole. If it kicks out, your 50 volt circuit is good,

Make sure your coin switches are not stuck in a partially closed position.

Make sure all Jones Plugs are fully seated. Coin door, Cabinet wires. Playfield to bottom board and bottom board harness to backbox connectors.

Try cleaning / filing the delay relay switch which is a single closed switch on the right side bottom as you look down. If that's not closed properly nothing will happen.