Measure transformer AC across a pair of lugs

The transformer secondaries have no ground reference, so set the meter to AC volts and put both probes on the pair of lugs or E points for that winding. DC outputs at TP1-TP3 and TP5 are read to ground with the meter on DC.

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35
• Stern MPU-100
• Stern MPU-200

Related tips

• Replacing the -49 VARO pair with one bridge

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part One, Clay Harrell (pinrepair.com)