Hmm. Space Mission has 10,000 point score reels and a light that comes on when you reach 100,000. I'll assume that that the problem is that you can't carry over from the 1000s score reel to the 10,000s score reel.
Space Mission 10k score reel (resized).jpg
Does it work any better for players 2-4? If so, you can assume that the switches on the Tilt relay and the 1000pt relay are good. That leaves just two things to check (in red): the connection through the Player Unit and the 9th position switch on the player 1 1000 point score reel. Use the wire colors on the schematic to find things and either short them one at a time with alligator clip test leads to see if that makes it work, or measure the resistance between points (with the power off) with your meter to see if those switches close.

/Mark

I don't follow what you tried, and it's hard to tell from your photos what the wire colors are. Maybe you could rephrase with wire colors instead so we can refer back to the schematic? I don't have this game nor do most people who might be able to help so the schematic is all we have.

If you're going the alligator clip route, there are two experiments to try first:

1) Clip one lead to the brown wire going into the player unit (from the 1000 point relay switch) and the other lead to the blue-yellow wire coming out of the player unit. This effectively removes the player unit switch from the circuit. If the 1000 point score reel can carry over to the 10,000 point score reel with the test lead in place the problem is likely in the player unit wiper, contact or wiring.

2) Clip one lead to the blue-yellow wire coming into the 10,000 point score reel 9th position switch (from the player unit) and the other lead to the white-brown wire coming out of the 10,000 point score reel. Note that this switch is probably not on the pc board, but more likely an actual switch following a cam mounted to the score reel hub. Check the wire colors to be sure. In this experiment the 10,000 point score reel should fire every time the 1000 point relay fires.

What do you see when you do these experiments?

You can manually test the 100K by flipping its switch. The 100Ks are at the top of the back box.

Until you get the free play jimmy-rigging figured out, you might try starting a game and then manually advancing the “coin” or “player count” unit on the mech board all the way up to 4 players and see if the game does play and advance from player to player as you test, might then help narrow down whether, as mentioned, this 10,000 issue is a problem with only pl 1, or also players 2-4.

Good tip @frenchmarky.

The brown wire is between the Player unit and a normally open switch on 1000 point relay, not the 1000 point score reel. You can clip to it on either end, either at the Player unit or at the relay switch. The brown wire might not be soldered to the fiber contact board on the Player unit. It might be tied directly to the metal frame of the Player unit.

That sounds like the right wires, but connecting blue-yellow to white-brown shouldn't make anything fire.

If it's not clear from the schematic in reply #2 above, we're trying to sort out why the 1st player 10,000 point score reel won't advance when the 1000 point score reel passes 9000, right? For that to happen three switches need to close:
- the 9th position switch on the 1000 point score reel
- the player 1 position switch on the Player unit
- the switch on the 1000 point relay (since players 2-4 aren't working, we can't assume this switch is working)

By clipping in your test lead around one switch at a time, you're bypassing that switch to see if the circuit works without it to try to figure out which one isn't working. So if you've started a game and the game thinks you're ready to play, bypassing one of more of these switches should get the 10,000 point score reel to advance.

Those relays, in order from the credit reel, are: 3&4 Reset, 1&2 Reset, 1000s, 100s, 10s.