The unregulated 12 volts can read 10 to 14 V
The +12 V logic feed is not regulated, so it moves with line voltage; anything from 10 to 14 VDC is normal and does not mean the power supply needs work.
Systems
Related tips
- Unregulated +12 V out of range
- Display supply low (under 90 V) after the resistors are changed
- Cross the legs when MJE15030/15031 replace SDS201/SDS202
- High-voltage supply rebuild parts, System 3 to 11C
- Fitting the high-voltage kit
- Spare diodes, capacitors and resistors for System 3-7
- Early Black Knights use the System 6 power supply
- Swapping power supply boards between generations
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part One, Clay Harrell (pinrepair.com)