Measure a flipper coil

Steps

• Game off. The centre lug, with both thick and thin wires, is the common.
• Centre lug to the thick-wire lug: about 3 ohms (power winding).
• Centre lug to the thin-wire lug: about 3 ohms at rest (EOS closed); push the flipper fully up to open the EOS and it should rise to about 125 ohms.
• More than about 5 ohms at rest means a pitted EOS: clean it.
• Other readings mean a bad coil; the hold winding fails more often than the power winding.
• Test the diode with one lead freed (0.4-0.6 one way, nothing the other), or just fit a new one.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• Replacing a flipper coil
• Fire a flipper coil by grounding it
• System 3-7 flipper coils are series wound
• Fitting parallel-wound flipper coils
• Matching a replacement flipper coil by resistance
• WPC flipper coils, weakest to strongest
• Williams 50 V fat flipper coils ranked by strength
• Flipper coil gets very hot

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)