The lower pop bumper locks on at power-up. Its transistor and pre-driver test good, a second power driver board does the same, and moving the plug to another pin moves the fault to a different coil; one pin of J127 reads very different resistance to the rest.

Lower pop locks on at power-up: J124 plug fitted on J128

Cause: The J124 plug had been fitted on header J128 (the manual does not list either), which connected 70 V coil power to the 20 V flashlamp circuit through J127 pin 8, the lower pop's return. This also overstresses capacitor C11.

Checks

• Compare every power driver board plug against a correct board or the wiki's connector notes, since the manual omits J124 and J128.
• Check C11 for doming and the flashlamp bulbs on that circuit for damage.

Fix

• Move the plug back to J124, then replace C11 and any blown bulbs if they were damaged.

Switch off at once if a coil locks on. A cross-connected plug can put coil voltage on low voltage parts.

Systems

• WPC Fliptronics

Games

• Black Rose

Related tips

• Gumball diverter, popper and two bumpers dead in test: faulty CPU ribbon
• GI string dead with a scorched connector
• Resets from worn power connectors between transformer, driver and CPU boards
• Burned power driver board traces at the header feeding AC to the Fliptronic board
• GI connectors on the driver board
• Two wires on one GI pin
• Repair a burnt GI connector on the driver board
• Check the AC power input connectors too

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