Editing Apple II General Maintenance (section)

== Power Supply Maintenance ==

Apple II power supplies are remarkably reliable but require periodic inspection and component replacement to prevent catastrophic failure.

=== Visual Inspection ===
Check monthly for:
* '''Bulging capacitors''' indicating imminent failure
* '''Burn marks''' on circuit board from overheated components
* '''Corroded connections''' at power connector
* '''Damaged insulation''' on transformer windings
* '''RIFA capacitor condition''' - cracked cases require immediate replacement

=== Voltage Verification ===
Test power supply output under load:
* '''+5V rail:''' Should measure 4.85V to 5.15V (5.00V optimal)
* '''+12V rail:''' Should measure 11.9V to 12.7V (12.0V optimal)  
* '''-12V rail:''' Should measure -11.9V to -12.7V (-12.0V optimal)
* '''-5V rail:''' Should measure -4.85V to -5.15V (-5.0V optimal)

Measure at the motherboard power connector with system running. Voltages outside these ranges indicate power supply problems requiring service.

=== Load Testing ===
For thorough testing without motherboard:
* '''+5V:''' Connect 3Ω 10W resistor for 1.67A load
* '''+12V:''' Connect 15Ω 10W resistor for 0.8A load
* '''-12V:''' Connect 100Ω resistor for light load
* '''-5V:''' Connect 100Ω resistor for light load

Power supplies that chirp or shut down under load have failing components. The adjustment potentiometer (if present) may restore proper voltage temporarily but doesn't fix underlying problems.

=== Capacitor Replacement Schedule ===
Preventive replacement extends power supply life:
* '''RIFA safety capacitors:''' Replace every 1-2 years (critical)
* '''Electrolytic capacitors:''' Replace every 10-15 years
* '''C7 (220µF 10V):''' Replace immediately if near power resistor

Modern replacements should use 105°C rated capacitors with low ESR specifications for improved reliability and longer service life.