The servo is good but the blinders still do not respond.

Tommy: blinder servo board never activates

Cause: The servo board never sees its clear signal go high. The board is fed from CPU connector CN3: P2 pin 1 +12 V, pin 3 clock, pin 4 data, pin 5 clear, pin 6 +5 V, pin 7 ground.

Checks

• Probe clock and data at P2 with a logic probe.
• Measure clear at P2 pin 5: it must reach 5 V.

Fix

• If clear never goes high, tie pin 1 of the 74LS174 at U4 to P2 pin 6 (+5 V) so the board stays enabled.

Systems

• Data East/Sega CPU Version 3b

Games

• The Who's Tommy Pinball Wizard

Related tips

• Tommy: adjust the blinder open and closed positions
• Tommy: blinders dead with good voltages and wiring
• Tommy: CPU and display EPROM types and latest versions

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Three, Clay Harrell (pinrepair.com)