The game will not finish booting: the MPU LED flashes seven times, the drop target banks reset, then it freezes. With the top saucer coil disconnected it boots to attract mode; reconnecting it and cycling coils in test freezes it again at the saucer.

MPU stops after 7 flashes unless the top saucer coil is unplugged: bad driver chip

Cause: A faulty chip in that coil's drive path rather than the coil, diode or driver transistor. The original poster reported swapping chips and named both the MPU PIA and an IC on the solenoid driver board as the culprit.

Checks

• Swap in a known good coil and diode to rule them out.
• Check the drive transistors, diodes and resistors on the solenoid driver board.
• Check the 43 V solenoid supply with the coil connected and disconnected.
• Swap the PIAs on the MPU if they are socketed, and check the decoder chips on the solenoid driver board.

Fix

• Replace the faulty chip feeding that solenoid (PIA on the MPU or the decoder on the solenoid driver board).

The poster also felt a slight shock from the side rails with the power off; check the wall outlet earth and the game's ground before working on it.

Systems

• Bally MPU AS-2518-17

Games

• Mata Hari

Related tips

• MPU stops before the seventh flash: check the 43 V at R113
• MPU on the bench always stops one flash short
• Resets from a bad MPU J4 power connector
• MPU boots only when U9 pins 39 and 40 are shorted
• MPU reboots right after the seventh flash
• What each MPU LED flash proves
• MPU boots only some of the time
• MPU LED locked on with no flicker: likely causes

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