Have you ever seen this game run?
It sounds like you have a short somewhere between the red-white wire that comes out of that Q relay switch you fixed, and the black wire that runs up the middle of the schematic from the 25v transformer winding. If you measure the resistance between those two with the power off, what do you get?
Finding a short can be tedious. Apart from visual inspections you'll need to try to eliminate parts of the circuit to see if that helps. Here are some things to try:
- Look carefully at switches and their solder tabs on the score motor and relays. Check for mangled or bent tabs, solder blobs, a loose screw or nut that fell from underneath the playfield, etc.
- Check that the Extra Ball adjustment (7I on the schematic) plug is plugged in and not dangling or touching anything else.
- See if disconnecting the jones plugs in the head helps. Try disconnecting the playfield too. (But just one at a time so you can narrow it down.)
- Look for burnt coils. An overheated coil may have developed a short inside between windings.
- Start at the Q relay switch at 13I on the schematic (the one you fixed) and follow the red-white wire up the right side of the schematic. Block off (with a piece of paper) the first switch on each circuit that goes to the left from the red-white wire. So for example block off the L relay switch at 8I first to see if that helps, then the P relay and Motor 3B switches at 7I, etc.