Part of the general illumination stays out, while a second GI string fed through another relay board works on only half the playfield.

Half the playfield GI out: loose connector on the GI relay board

Cause: A loose connector on the GI relay board driven by solenoid 9. That board feeds the next relay board, so its fault affects both.

Checks

• On these relay boards, the red wire is the relay coil supply (banded side of the coil diode) and the brown wire goes back to the CPU driver transistor.
• The other wires are the AC GI feed in on the relay's common contacts and the GI out to the lamps on its contacts; check each connection with the game on GI test.

Fix

• Reseat or repin the loose connector on the relay board and reflow its header.

Systems

• Williams System 11B

Games

• Space Station

Related tips

• System 11 general illumination

Source: Pinball Repair help group!! (Facebook group)