Why a Gottlieb coil can't go in a Bally game (and vice versa)

A Gottlieb pop bumper coil (25 V) is about 3 ohms; a Bally one (50 V) is about 10 ohms, though both look alike. Swapped, the Gottlieb coil is far too strong in a Bally and the Bally coil far too weak in a Gottlieb. As a rule of thumb, going two wire gauges thinner doubles resistance per foot, so a 20-gauge 25 V coil becomes roughly a 22-gauge coil for 50 V with the same turns.

Systems

• Electro-mechanical

Related tips

• Bally C0- coil numbers and their replacements
• Old Bally E-184 coil numbers and their replacements
• Gottlieb coil wrappers are colour coded
• Bally coils with Midway cross-reference numbers
• Gottlieb EM coil windings, resistance and wrapper colour
• Coil stops by maker
• Coil sleeves and plungers to keep
• Typical EM coil resistances

Source: Repairing Electro-Mechanical (EM) Coin Operated Games to 1978, Part Two, Clay Harrell (pinrepair.com)