Top Score EX relay (resized).jpg
The circuit that fires the EX relay starts with three switches on the lower left (P, AX & Q), then goes through the Player Unit wiper disk, then through the 3-5 balls per game adjustment and finally through a switch on the EX relay itself in the red box. The DX and FX relays go through very similar circuits. We know that the DX and FX relays work as they should so the first three switches have to be good since they're used by all three relays. If one of the first three switches were bad none of the three relays would work, nor would the Ball in Play lights also shown above.

The Player Unit is shown at the start of the game with the arrow in the upper left corner of the unit pointing to position 0 which turns on the #1 Ball in Play light, and the DX relay in a 3 ball game. When the ball drains the Player Unit steps one or more steps and the arrow on the schematic moves down to complete different circuits.

On a 5 ball game, the EX relay should fire when the Player Unit (and the arrow on the schematic) reaches position 12 which completes the circuit to the #4 Ball in Play light and the EX relay via the GR+RED (green and red in equal proportion) wire and the RED-GR (red with green tracer) wire. The normally closed switch on the EX relay in the red box opens as soon as the EX relay trips to cut power and prevent the coil from overheating.

Assuming all the Ball in Play lights work we also know that the Player Unit must be doing its thing. That leaves the 3-5 Balls Per Game adjustment and the switch on the EX relay (in the red box) as possible causes. The EX relay switch seems more likely since the relay doesn't work in either 3 or 5 ball games.

Even though the EX relay switches all appear to open and close as they should you can't be sure that a closed switch is actually conducting electricity unless you've tested it with a meter or some other electrical device. The contacts may have oxidized or there may be soot between the contacts that insulate one contact from the other even when the switch is closed.

Suspecting the EX relay switch in the red box you could:
- try gently cleaning the switch contacts or
- jumper across the switch with an alligator clip test lead and see if the EX relay fires when it should

The EX relay switch in the red box has a red wire with a thin green tracer on one side and a short jumper of unspecified color on the other side that leads directly to one of the EX relay coil solder lugs. In your photo it looks like the short jumper wire is orange. If that's the case you'd jumper from the red wire with thin green tracer to the orange wire.