Matching a replacement flipper coil by resistance

Steps

• Measure the original coil from the centre lug to each outer lug.
• The lower reading (about 3-6 ohms) is the power winding: this is the one to match. The higher (about 90-150 ohms) is the hold winding and need not match.
• Pick a physically correct coil with the same or similar power resistance. A lower resistance is stronger: half an ohm is over 10% and makes a big difference.
• Do not overdo it; flippers only need to reach the top of the playfield, and too much power breaks plastics and posts.
• Replace the EOS and cabinet switches at the same time.

Systems

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

Related tips

• Measure a flipper coil
• Fire a flipper coil by grounding it
• System 3-7 flipper coils are series wound
• Fitting parallel-wound flipper coils
• WPC flipper coils, weakest to strongest
• Replacing a flipper coil
• Williams 50 V fat flipper coils ranked by strength
• Power at the flipper coil but no flip

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