A relay or solenoid makes a constant hum or buzz.
A coil hums continuously
Cause: The coil is being held on by a stuck or shorted switch. A few EM relays are meant to be on all the time, but solenoids almost never are (rare 1950s exceptions).
Checks
- Identify the humming coil and whether it should be on at that moment.
Fix
- Switch the game off before the coil burns, then find and free the stuck switch.
Systems
- Williams System 3
- Williams System 4
- Williams System 6 / 6A
- Williams System 7
- Williams System 9
- Williams System 11
- Williams System 11A
- Williams System 11B
- Williams System 11C
- WPC Alpha-Numeric
- WPC Dot Matrix
- WPC Fliptronics
- WPC DCS
- WPC-Security (WPC-S)
- WPC-95
- Bally MPU AS-2518-17
- Bally MPU AS-2518-35
- Stern MPU-100
- Stern MPU-200
- Bally 6803
- Gottlieb System 1
- Gottlieb System 80
- Gottlieb System 80A
- Gottlieb System 80B
- Gottlieb System 3
- Data East CPU Version 1/2
- Data East CPU Version 3
- Data East/Sega CPU Version 3b
- Capcom
- Electro-mechanical
Related tips
- Replacing a solenoid coil
- Relay or solenoid?
- Testing the diode on a coil
- Coil diode polarity
- Ordering the right coil
- Reading a gauge-and-turns coil number
- Renewing coil sleeves on action coils
- Finding a burned solenoid coil
Source: Pinball Machine Care & Maintenance, Bernard B. Kamoroff (Bell Springs Pinball Alley)