Apple II General Maintenance

Apple II with Case Open

The Apple II General Maintenance guide covers essential procedures for preserving and maintaining Apple II, Apple II Plus, and Apple IIe computers. Regular maintenance prevents common failures that develop after decades of use, particularly chip oxidation, socket corrosion, and power supply degradation. This comprehensive guide addresses cleaning procedures, component inspection, chip reseating, and preventive measures specific to the Apple II family.

Safety Precautions

Working on Apple II computers requires careful attention to electrical safety and component protection from static discharge. The computer's age makes components particularly vulnerable to damage from improper handling.

Electrical Safety

Before performing any maintenance:

• Always disconnect power from the computer and wait at least 30 minutes for capacitors to discharge
• Remove all peripheral cards from expansion slots before working on the motherboard
• Disconnect the keyboard cable at the motherboard connector to prevent accidental shorts
• Never work on power supplies with the unit plugged in - even when switched off, lethal voltages remain present

The power supply contains high voltage components that retain charge after disconnection. The main filter capacitor (typically 2200µF) can hold dangerous voltage levels for extended periods. If power supply work is necessary, discharge capacitors safely using a 10kΩ resistor across the terminals, never with a screwdriver or metal object which can cause component damage.

Static Protection

The MOS technology chips used in Apple II computers are extremely sensitive to electrostatic discharge. Components from the 1970s and 1980s are particularly vulnerable, with damage occurring from as little as 10 volts of static electricity - well below the 1500 volt threshold humans can perceive.

Essential static precautions include:

• Use an anti-static mat when working on circuit boards, connecting it to a proper ground point
• Wear an anti-static wrist strap connected to ground through a 1MΩ resistor for safety
• Store chips in anti-static foam or conductive bags when removed from sockets
• Handle chips by their edges only, never touching the pins directly
• Work in 70-90% humidity when possible to reduce static buildup
• Avoid wearing polyester clothing or working near plastic materials

When anti-static equipment is unavailable, touch both hands to a grounded metal surface before handling chips. Aluminum foil or anti-static bags from electronic components can serve as temporary work surfaces, but never power the computer while on these conductive materials.

Chip Reseating

The single most common problem with Apple II computers is poor socket connections caused by oxidation over decades. Reseating chips properly resolves the majority of boot failures and system instability issues.

Identifying Problem Connections

Symptoms of oxidized connections include:

• System fails to boot or displays garbage characters
• Random crashes during operation
• Keyboard keys not responding or producing wrong characters
• Memory errors appearing intermittently
• Video display problems including color fringing or missing text

The oxidation forms an insulating layer between chip pins and socket contacts, creating high-resistance connections that prevent proper signal transmission. This problem is particularly severe in Apple II and II Plus models where all chips are socketed.

Proper Reseating Technique

For systematic reseating:

1. Document chip positions before removal - photograph the motherboard or create a diagram showing chip orientations
2. Use a proper IC extractor - insert the tool ends under opposite corners of the chip
3. Rock gently while lifting - never pull straight up which can bend pins
4. Inspect each chip for bent or corroded pins before reinsertion
5. Clean pins if oxidized using a pencil eraser or fiberglass pen
6. Align carefully - ensure all pins enter the socket before pressing down
7. Press firmly and evenly using thumb pressure on the center of the chip

Work methodically through one row at a time, completing each chip before moving to the next. The 6502 CPU, character generator ROM, and RAM chips in rows C, D, and E are most critical for basic operation.

Special Considerations for Different Models

Apple II (Integer BASIC models):

• Pay special attention to the 6502 processor at location A-7
• The Integer BASIC ROMs at D0, D8, E0, E8 must be firmly seated
• Color killer transistor connections may need cleaning

Apple II Plus:

• Applesoft ROMs at D0, D8, E0, E8, F0, F8 are critical
• Memory select blocks (if present) require careful handling
• 4116 RAM chips are particularly failure-prone

Apple IIe:

• Many chips are soldered rather than socketed
• Focus on socketed custom chips: IOU, MMU, HAL, and Video ROM
• Extended 80-column card connections need regular cleaning

Internal Cleaning

Dust accumulation inside Apple II computers causes overheating and accelerates corrosion. Regular internal cleaning extends component life and improves reliability.

Motherboard Cleaning

For routine dust removal:

1. Use compressed air held at a 45-degree angle to avoid forcing dust deeper into sockets
2. Work from top to bottom allowing dust to fall away from cleaned areas
3. Focus on heat-generating areas around the power supply connector and voltage regulators
4. Clean between expansion slots where dust accumulates heavily

For thorough cleaning of heavily contaminated boards:

1. Remove all socketed ICs and store safely in anti-static foam
2. Wash with warm water and dish soap using a soft brush for stubborn areas
3. Rinse thoroughly with distilled water to remove all soap residue
4. Shake vigorously to remove water from sockets and under components
5. Dry for minimum 48 hours in warm, dry location before reassembly
6. Use isopropyl alcohol (99% concentration) for final cleaning of contacts

This water washing method effectively removes decades of contamination but requires complete drying before power application. Trapped moisture causes immediate failure and corrosion.

Keyboard Maintenance

Apple II keyboards accumulate debris that causes sticky or non-responsive keys.

Keycap cleaning:

1. Remove keycaps carefully using an IC extractor or keycap puller
2. Soak in warm soapy water for 30 minutes
3. Scrub with soft brush to remove ingrained dirt
4. Rinse and dry completely before replacement

Keyswitch cleaning:

1. Apply 99% isopropyl alcohol to switch mechanism using squeeze bottle
2. Work switch 50-100 times to distribute cleaner and break through oxidation
3. Allow complete evaporation before testing
4. Repeat if necessary for stubborn switches

The encoder chip (MM5740 on early models, AY-3600 on later) is extremely static-sensitive and expensive to replace. Never touch this chip without proper grounding.

Case Maintenance

The injection-molded plastic cases yellow and become brittle with age, requiring careful cleaning to avoid damage.

Basic Cleaning

For routine case cleaning:

• Mix 50% household bleach with 50% water for effective cleaning that removes yellowing
• Apply with soft cloth avoiding abrasive materials that scratch plastic
• Use cotton swabs for cleaning around raised Apple logo and ventilation slots
• Rinse with clean water to remove bleach residue
• Apply furniture polish like Pledge for protective finish

Removing Stubborn Stains

For persistent marks:

• Isopropyl alcohol removes adhesive residue and ink marks
• Magic Eraser (melamine foam) gently abrades surface contamination
• Ajax cleanser with toothbrush removes deep stains but dulls surface
• Restore shine by rubbing vigorously with paper towels

Painted cases require extra care - test cleaning products on hidden areas first. The paint on Bell & Howell black Apple II Plus models is particularly fragile.

Retrobrighting

Main article: Retrobrite

Severely yellowed cases benefit from hydrogen peroxide treatment:

1. Disassemble completely removing all metal parts
2. Clean thoroughly to remove surface contamination
3. Apply hydrogen peroxide cream (40 volume) evenly
4. Expose to UV light or direct sunlight for 4-6 hours
5. Rinse completely and dry before reassembly

Results vary depending on plastic formulation and original yellowing cause. Some cases respond dramatically while others show minimal improvement.

Expansion Slot Maintenance

The seven expansion slots accumulate oxidation that prevents cards from functioning properly.

Cleaning Procedures

For each slot:

1. Spray contact cleaner (DeoxIT D5 preferred) into slot opening
2. Insert and remove a sacrificial card 10-15 times to scrub contacts
3. Allow cleaner to evaporate completely before installing cards
4. Apply contact enhancer (DeoxIT Gold) for long-term protection

Card Edge Connector Treatment

Expansion cards require similar maintenance:

• Clean edge connectors with isopropyl alcohol and lint-free cloth
• Polish with pencil eraser for stubborn oxidation
• Never use sandpaper which removes gold plating
• Check for worn contacts appearing as dark spots on gold fingers

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.

ROM and RAM Identification

Understanding chip identification helps diagnose problems and source replacements.

ROM Chip Layout

Apple II Integer BASIC:

• Monitor ROM: F8 (2716)
• Integer BASIC: D0, D8, E0, E8 (2316B mask ROMs)
• Sweet16: F0 (2316B mask ROM)

Apple II Plus Applesoft:

• Monitor ROM: F8 (2716)
• Applesoft BASIC: D0, D8, E0, E8, F0 (2316B mask ROMs)

Apple IIe:

• CD and EF ROMs contain entire system firmware
• Video ROM for character generation
• Can be upgraded to Enhanced IIe with chip kit

RAM Configuration

Identifying RAM chips:

• 4116: 16K × 1 bit chips (need 8 for 16KB)
• 4164: 64K × 1 bit chips (need 8 for 64KB)
• Date codes: YYWW format (year and week of manufacture)

Memory configurations vary:

• Apple II: 4K, 8K, 12K, 16K, 20K, 24K, 32K, 36K, 48K
• Apple II Plus: Usually 48K, rarely 32K or 16K
• Apple IIe: 64K standard, expandable to 128K

Memory select blocks on early boards show configuration:

• Jumper blocks marked 4K or 16K
• Located left of RAM chips near power supply
• Most II Plus lack these, indicating 48K standard

Voltage Regulator Maintenance

The motherboard voltage regulators require periodic inspection to prevent heat-related failures.

Heat Sink Inspection

Check quarterly for:

• Loose mounting screws reducing heat transfer
• Dried thermal compound appearing white and crumbly
• Bent fins restricting airflow
• Dust accumulation insulating heat sink

Clean heat sinks with compressed air and replace thermal compound every 5 years using quality silver-based paste.

Regulator Testing

Measure regulator output:

• 7812 regulator: +12V ±0.5V
• 7912 regulator: -12V ±0.5V
• 7905 regulator: -5V ±0.25V

Regulators running extremely hot or producing incorrect voltages require replacement. Use 1A rated versions for improved thermal margin.

Preventive Maintenance Schedule

Regular maintenance prevents most failures:

Monthly

• Run computer for minimum 30 minutes to prevent capacitor deterioration
• Exercise all keys to prevent oxidation buildup
• Check power supply voltages if test equipment available
• Inspect for signs of overheating or component failure

Quarterly

• Clean case exterior and keyboard
• Check expansion card connections
• Verify cooling paths clear of obstruction
• Test with diagnostic software

Annually

• Open case and clean interior thoroughly
• Reseat critical chips (CPU, ROMs, character generator)
• Inspect all capacitors for bulging or leakage
• Clean expansion slots and card edges
• Measure and document power supply voltages
• Check RIFA capacitor condition

Every 5 Years

• Consider full chip reseating
• Replace thermal compounds
• Deep clean motherboard if heavily contaminated
• Consider preventive capacitor replacement

Storage Guidelines

Proper storage prevents deterioration during periods of non-use:

Environmental Conditions

Optimal storage requires:

• Temperature: 60-75°F (15-24°C)
• Humidity: 30-50% relative humidity
• Light exposure: Avoid direct sunlight and fluorescent lighting
• Dust protection: Use dust covers or sealed containers

Include silica gel packets in storage containers to control humidity. High humidity accelerates corrosion while low humidity increases static electricity risk.

Preparation for Storage

Before extended storage:

1. Clean thoroughly inside and out
2. Remove batteries from any peripherals
3. Apply contact preservative to all connectors and card edges
4. Wrap in anti-static material - never use plastic bags
5. Document condition including any known issues
6. Store vertically to minimize board flexing
7. Include desiccant packets for humidity control

Reactivation After Storage

When returning to service:

1. Inspect for rodent damage to cables and boards
2. Check for corrosion particularly around battery holders
3. Clean and reseat all chips before first power-up
4. Reform capacitors by running for short periods initially
5. Test voltages before connecting to motherboard
6. Run diagnostics to verify proper operation

Troubleshooting Common Problems

These maintenance procedures resolve most Apple II problems:

No Power or No Boot

1. Check power supply voltages
2. Reseat all chips systematically
3. Clean power connector at motherboard
4. Verify ROM chips in correct positions
5. Test with minimal RAM configuration

Garbage Screen Display

1. Reseat character generator ROM
2. Clean and reseat all RAM chips
3. Check video timing crystal
4. Verify motherboard jumpers for PAL/NTSC

Keyboard Problems

1. Clean affected keyswitches with alcohol
2. Check keyboard connector at motherboard
3. Reseat encoder chip carefully
4. Verify cable continuity

Disk Drive Issues

1. Clean drive heads with isopropyl alcohol
2. Check cable connections
3. Clean card edge connector
4. Verify controller card seated properly

Test Equipment Recommendations

Basic maintenance requires minimal equipment:

• Digital multimeter for voltage measurements
• Anti-static mat and wrist strap for component protection
• IC extraction tool for chip removal
• Contact cleaner (DeoxIT D5) for oxidation removal
• 99% isopropyl alcohol for cleaning
• Compressed air for dust removal
• Soft brushes for scrubbing boards
• Cotton swabs for detail cleaning

Advanced troubleshooting benefits from:

• Oscilloscope (100MHz minimum) for signal analysis
• Logic probe for digital signal testing
• EPROM programmer for ROM replacement
• Component tester for capacitor ESR measurement

Related Maintenance Pages

• Apple II Troubleshooting Guide
• Apple II Capacitor Replacement Guide