Measuring a pre-Fliptronics flipper coil and its EOS switch

Steps

• Game off. Find the common lug: the outer lug on the banded end of the diode, carrying both the thick and thin windings.
• Common lug to the thick-wire lug: about 3 ohms (the power winding).
• Common lug to the thin-wire lug: about 3 ohms with the flipper at rest (EOS closed); push the flipper fully up by hand to open the EOS and it should read about 125 ohms.
• More than about 5 ohms at rest means pitted EOS contacts; clean them for stronger flippers.
• No change to 125 ohms at full stroke means the EOS is not opening and the coil will overheat. No reading at full stroke means the hold winding is broken, the more common failure.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix

Related tips

• Pre-Fliptronics flipper coil wiring
• Pre-Fliptronics: weak flipper
• Flipper buttons not seen by the game (pre-Fliptronics)
• Pre-Fliptronics flipper coil smokes when held up
• Pre-Fliptronics games need a driver board with the flipper relay
• End-of-stroke switches: pre-Fliptronics versus Fliptronics
• EOS switch: normally closed on older games, normally open on Fliptronics
• Pre-Fliptronics: flipper runs very hot or sticks up and burns

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Two, Clay Harrell (pinrepair.com)