Apple Extended Keyboard II

Apple Extended Keyboard II
Apple Extended Keyboard II M3501 with Alps SKCM Cream Damped switches
Manufacturer	Apple Computer, Inc.
Type	Computer keyboard
Discontinued	1994
Price	US$163 (retail)
Interface	Apple Desktop Bus
Compatible	All ADB-equipped Macs, Apple IIGS
Dimensions	475 mm W × 196 mm D × 41 mm H (maximum)
Weight	1.73 kg (3.81 lbs)
Predecessor	Apple Extended Keyboard (M0115)
Successor	AppleDesign Keyboard (M2980)
Model	M3501, M0312

The Apple Extended Keyboard II (AEK II) was Apple's refined professional keyboard introduced October 15, 1990, as the successor to the Apple Extended Keyboard. First bundled with the Macintosh IIsi, the keyboard maintained the 105-key extended layout while incorporating ergonomic refinements including an adjustable rear foot and quieter mechanical switches. The keyboard utilized Alps SKCM Cream Damped switches as its primary configuration, though variants with Salmon Alps, White Alps, and Mitsumi mechanical switches were produced across four manufacturing facilities. Production continued until 1994 when Apple transitioned to the cost-reduced AppleDesign Keyboard featuring rubber dome switches.

Design Philosophy

The Extended Keyboard II emerged from a collaborative design effort initiated in 1988 when Apple Ireland commissioned Design ID, a Limerick-based industrial design consultancy. Bryan Leech and Peter Sheehan developed initial concepts focusing on ergonomic improvements mandated by emerging European workplace standards. The design team implemented what they termed an "S-curve profile" - a compound curve that positioned the function keys on a flattened plane while maintaining an upward slope through the alphanumeric section.

This profile contrasted with the original Extended Keyboard's continuous convex curve. The new design eliminated the deep case cavity behind the function keys, reducing material usage while maintaining structural integrity. Steven Peart from frogdesign contributed supplementary industrial design work focusing on Design for Manufacture and Assembly (DFMA) principles. Dexter Francis served as Apple's in-house project lead from the Peripheral Products Group.

The first working prototype was constructed at Design ID by Richard Howe, Donal Ryan, and John Fitzgerald. The team specified quieter switch mechanisms after extensive testing revealed the dampened Alps variants met acoustic requirements for office environments while preserving tactile feedback quality.

Physical Construction

Case Design

The AEK II case employed a two-piece construction with distinctive ergonomic features:

• Upper housing: S-curve profile with integrated key wells
• Lower housing: Flat base with retractable adjustment mechanism
• Material: ABS plastic in Platinum gray (Pantone 429C)
• Finish: Textured matte surface matching Snow White design language
• Apple logo: Relocated to upper left corner (from lower left on M0115)

Adjustable Foot Mechanism

A single retractable bar spanning the keyboard width provided typing angle adjustment:

• Retracted position: 6° typing angle
• Extended position: 11° typing angle
• Construction: Reinforced ABS with internal spring mechanism
• Common issue: Mechanism frequently seized due to plastic deformation

Template Posts

Two cylindrical posts flanked the function key row:

• Height: 12mm above case surface
• Diameter: 5.5mm
• Purpose: Secure application-specific function key overlays
• Material: Injection-molded ABS matching case color

Internal Structure

• Mounting plate: 1.5mm steel, powder-coated black
• PCB layers: Double-sided with surface-mount components
• RF shield: Black conductive liner between PCB and lower case
• Stabilizer system: Alps-specific wire stabilizers with plastic clips

Model Variants

M3501 (Primary Model)

Production: 1990-1994

• Markets: Worldwide distribution
• Manufacturing: USA, Mexico, Ireland, Japan
• Switch types: All variants produced
• FCC ID: BCGM3501

M0312 (Early Variant)

Production: 1990-1992

• Markets: North America primarily
• Manufacturing: USA, Mexico
• Switch types: Cream damped Alps exclusively
• FCC ID: BCGM0312
• Note: Some M3501 units carry M0312 serial suffixes

Manufacturing Facilities

United States Production

Location: Fremont, California

• Period: 1990-1994
• Switch types: Cream damped, Salmon Alps
• Serial prefix: Various
• Market focus: North American distribution

Mexico Production

Location: Manufacturing facility details limited

• Period: 1991-1994
• Switch types: Cream damped Alps
• Copyright markings: 1991, 1995
• Market focus: North American distribution

Ireland Production

Location: Cork facility

• Period: 1989-1995
• Switch types: Cream damped Alps exclusively
• Serial characteristics: No 'S' dampener symbol
• Market focus: European distribution

Japan Production

Location: Mitsumi Electric facilities

• Period: 1989-1991
• Switch types: Mitsumi standard mechanical only
• PCB manufacturer: Mitsumi
• Market focus: Asian markets, limited distribution

Switch Technologies

Alps SKCM Cream Damped (Primary)

Specifications:

• Type: Tactile, dampened
• Actuation force: 70g ± 10g
• Pre-travel: 2.0mm
• Total travel: 3.5mm
• Dampening: Rubber bumpers on slider sides
• Sound signature: Muted "thock"
• Lifespan: 10 million actuations

The Cream damped switches represented Alps Electric's response to workplace noise concerns. Small rubber inserts on either side of the slider cushioned both downstroke and upstroke impacts, creating a quieter typing experience while maintaining the tactile characteristics of the SKCM design. The dampening mechanism positioned the tactile point higher in the travel, occasionally leading users to mistake these for rubber dome switches.

Alps SKCM Salmon

Specifications:

• Type: Tactile, non-dampened
• Actuation force: 70g ± 10g
• Pre-travel: 2.0mm
• Total travel: 3.5mm
• Sound signature: Sharp "click-clack"
• Production: USA facilities only

Salmon Alps switches appeared exclusively in USA-manufactured units. These switches lacked the rubber dampeners of the Cream variant, producing a more pronounced acoustic signature with harder bottom-out characteristics. The tactile leaf design remained identical to Cream switches, providing similar actuation feel without sound dampening.

Alps SKCM White Damped

Specifications:

• Type: Tactile, dampened
• Actuation force: 70g ± 10g
• Slider color: Pure white (versus cream)
• Production: Rare variant, USA/Mexico
• Tactile leaf: Modified design from Cream

White damped Alps represented a rare production variant with pure white sliders. While mechanically similar to Cream damped switches, the internal tactile leaf employed a slightly different geometry. Users report virtually identical typing feel despite the mechanical differences.

Mitsumi Standard Mechanical

Specifications:

• Type: Linear to faintly tactile
• Actuation force: 65g ± 10g
• Slider compatibility: Alps mount
• Color: All-white construction
• Production: Japan exclusively

Mitsumi switches appeared only in Japanese-manufactured units. These switches utilized Alps-compatible keycap mounts while employing a simplified internal mechanism. The switches exhibited minimal tactility, operating nearly linearly with significantly reduced acoustic output compared to Alps variants.

Alps SKCL Lock (Caps Lock)

All variants utilized the Alps SKCL Lock switch for Caps Lock:

• Mechanism: Physical latching system
• Housing color: Dark gray (Cream/White keyboards) or Cream (Salmon keyboards)
• Operation: Mechanical lock-down when engaged
• Acoustic: Distinctive click on state changes

Technical Specifications

Physical Dimensions

• Width: 475mm (18.7 inches)
• Depth: 196mm (7.7 inches)
• Height (front): 25mm (1.0 inch)
• Height (rear, foot retracted): 41mm (1.6 inches)
• Height (rear, foot extended): 58mm (2.3 inches)
• Weight: 1.73kg (3.81 lbs)
• Cable length: 1.2m coiled (extends to 1.8m)

Electrical Specifications

• Interface: Apple Desktop Bus (ADB)
• Connectors: Two 4-pin mini-DIN ports (left and right)
• Power consumption: 25mA typical, 50mA maximum
• Operating voltage: 4.75V - 5.25V DC
• Data rate: 10 kbit/s maximum
• Bus addressing: Default address $2

ADB Implementation

• Device handler ID: $02 (standard), $03 (extended protocol)
• Polling rate: 100 Hz maximum
• Key rollover: 2-key minimum guaranteed, 6-key typical
• Communication: Bidirectional serial protocol

Register Configuration

Register 0: Key event buffer

• 2-byte buffer for simultaneous key events
• 7-bit keycode + 1-bit press/release flag

Register 1: Reserved

Register 2: LED and modifier status

• Bit 0: Num Lock LED
• Bit 1: Caps Lock LED
• Bit 2: Scroll Lock LED

Register 3: Device configuration

• Handler ID selection
• Service request flags

Internal Design

PCB Architecture

Controller: Toshiba TC4515BP binary controller

• 8-bit microcontroller
• Integrated ADB protocol handling
• Key matrix scanning at 1000 Hz
• Debounce processing

Component layout:

• Surface-mount technology throughout
• Dual ADB ports on separate daughter boards
• Ribbon cable interconnects
• Component count: ~35 discrete parts

Assembly Process

1. Steel plate preparation and powder coating
2. Switch insertion into plate (105 positions)
3. PCB alignment and mounting to plate assembly
4. Wave soldering of switch pins
5. Manual installation of stabilizers
6. ADB port PCB installation
7. Case assembly (front clips, rear tabs)
8. Cable routing and strain relief
9. Quality control testing

Key Matrix Design

• Matrix size: 8×16 (128 possible positions)
• Ghost key prevention: Diode per switch
• Scan rate: 1000 Hz internal, 100 Hz ADB report
• Debounce period: 5ms typical

Keycap Specifications

Materials and Manufacturing

• Alphanumeric keys: PBT plastic
• Spacebar: ABS plastic (yellowing prone)
• Manufacturing: Dye sublimation
• Thickness: 1.3mm average
• Surface texture: Fine matte finish

Profile Characteristics

The AEK II employed Apple's proprietary keycap profile:

• Function row: Vertical stem mounting, tallest profile
• Number row: Standard height reference
• QWERTY row: 1mm lower than number row
• Home row: 2mm lower than number row
• Bottom row: 3mm lower than number row
• Spacebar: Custom sculpted, centered dip

This profile appeared shifted one row downward compared to standard Cherry or OEM profiles, with keycap skirts matching the keyboard's curved upper surface.

Typography

• Font: Univers 57 Oblique
• Application: Dye sublimated in dark gray
• Alignment: Centered on all keys
• Special keys: Text labels rather than symbols
• Language variants: ISO layouts used local language labels

Serial Number Format

Standard Format

Structure: PPYWWNNNNNN-MODEL

• PP: Plant code
• Y: Year digit (0=1990, 1=1991, etc.)
• WW: Week number (01-52)
• NNNNNN: Sequential unit number
• MODEL: M3501 or M0312 suffix

OEM Identification

First letter indicates manufacturer:

• A: Alps Electric
• M: Mitsumi Electric

Dampener Indicator

Units with 'S' symbol in square on label indicate dampened switches (USA/Mexico only).

Software Compatibility

Operating System Support

• Classic Mac OS: System 6.0.7 through Mac OS 9.2.2
• Mac OS X: 10.0 through 10.3 (with adapters)
• A/UX: Full native support
• Apple IIGS: GS/OS and ProDOS compatible
• BeOS: Third-party driver available
• Linux: Kernel support on PowerPC and x86 (with adapter)

Extended Protocol Features

Handler ID $03 enabled:

• Left/right modifier key differentiation
• Extended function key support (F13-F15)
• Programmable key repeat rates
• Enhanced key event reporting

Special Key Functions

• Power key: Direct system power control
• Command-Control-Power: Force restart
• Command-Option-Escape: Force quit dialog
• Command-Option-P-R: PRAM reset (at startup)

Common Issues and Solutions

Mechanical Problems

Troubleshooting Guide

Problem	Cause	Solution	Difficulty
Adjustment bar stuck	Plastic deformation	Disassemble and lubricate mechanism	Moderate
Key chatter/repeat	Switch contact oxidation	Clean with isopropyl alcohol	Easy
Dead keys	Failed switch	Replace individual switch	Moderate
Stabilizer rattle	Worn clips	Replace stabilizer clips	Moderate
Case yellowing	UV exposure, brominated flame retardants	Retrobright treatment	Moderate
ADB not recognized	Cable damage	Test continuity, replace cable	Difficult
Intermittent connection	Corroded ADB pins	Clean with contact cleaner	Easy

Adjustment Mechanism Restoration

The height adjustment mechanism commonly seized due to plastic stress:

1. Remove bottom case screws
2. Extract spring from adjustment bar
3. Apply silicone lubricant to pivot points
4. Work mechanism repeatedly to distribute lubricant
5. Reassemble with spring properly seated

Switch Maintenance

Basic cleaning:

1. Remove keycap with wire puller
2. Apply 3-5 drops 90%+ isopropyl alcohol
3. Actuate switch 20-30 times
4. Allow 10 minutes evaporation
5. Test and repeat if necessary

Deep cleaning (requires desoldering):

1. Desolder switch from PCB
2. Open housing (4 retention tabs)
3. Clean contacts with alcohol
4. Inspect spring and leaf condition
5. Apply dielectric grease to slider rails
6. Reassemble and test before resoldering

Disassembly Procedure

Required Tools

• Phillips screwdriver #1
• Plastic spudgers
• Keycap puller (wire type preferred)
• Isopropyl alcohol 90%+
• Cotton swabs
• Anti-static mat

Step-by-Step Process

Case separation:

1. Remove four Phillips screws from bottom
2. Note screw lengths (rear screws longer)
3. Release ADB port PCBs using spudger
4. Push ribbon cables up through slots
5. Separate case halves carefully

PCB removal:

1. Press two retention tabs backward with thumbs
2. Lift PCB assembly while pressing tabs
3. Clear five front edge clips
4. Remove complete plate/PCB assembly

Adjustment mechanism:

1. Remove spring from adjustment bar
2. Do not disassemble pivot mechanism
3. Clean and lubricate if stuck

Modern Usage

ADB to USB Conversion

Hardware solutions:

• Griffin iMate: Original solution (discontinued, incompatible past Mac OS 10.3)
• Wombat: Current recommended adapter, bidirectional support
• TMK Converter: Open-source DIY option
• Drakware ADB2USB: Commercial cable solution

Conversion considerations:

• Power key requires remapping on modern systems
• Extended protocol features lost in translation
• Typical latency: 1-2ms with quality adapters
• Full NKRO not supported due to ADB limitations

Restoration Best Practices

Retrobrighting procedure:

• Solution: 12% hydrogen peroxide cream
• Application: Even coating avoiding labels
• UV exposure: 6-8 hours with rotation
• Temperature: 20-25°C optimal
• Expected results: 60-80% yellowing reduction

Keycap restoration:

• Cleaning: Warm water with denture tablets
• Soak duration: 4-6 hours maximum
• Stubborn stains: Soft brush with dish soap
• Avoid: Acetone, bleach, or abrasive cleaners

Market Value and Collecting

Current Market Prices (2024)

Approximate Values (USD)

Condition	Cream Damped	Salmon Alps	White Damped	Mitsumi
Poor (yellowed, worn)	$75-125	$100-150	$125-175	$50-75
Good (functional, some yellowing)	$125-200	$150-250	$175-275	$75-125
Excellent (minimal yellowing)	$200-350	$250-400	$275-425	$125-200
Mint (no yellowing, boxed)	$350-500	$400-600	$425-650	$200-300

Authentication Guidelines

• Verify model number on bottom label
• Check serial number format consistency
• Confirm switch type via keycap removal
• Inspect stabilizer clip colors (era-specific)
• Verify template posts present and intact
• Look for dampener symbol if applicable

Preservation Recommendations

• Storage temperature: 15-25°C
• Relative humidity: 40-60%
• Avoid direct sunlight exposure
• Store flat with keys facing up
• Use dust cover or sealed bag
• Maintain cable without tight coiling

Production Statistics

Based on serial number analysis and community data:

• Total production: Estimated 2.5 million units
• Cream damped: ~70% of production
• Salmon Alps: ~15% of production
• White damped: ~5% of production
• Mitsumi: ~10% of production
• Survival rate: Estimated 20-25% functional

Design Legacy

The Apple Extended Keyboard II established several lasting precedents:

Ergonomic innovations:

• Adjustable typing angle became standard
• S-curve profile influenced later designs
• Quieter switches for office environments

Construction standards:

• Steel plate mounting remained premium standard
• Modular assembly improved serviceability
• Quality benchmarks for keycap materials

Market influence:

• Final Apple mechanical keyboard
• Defined expectations for professional keyboards
• Influenced modern mechanical keyboard revival

The AEK II's reputation as Apple's finest keyboard stems from its balance of tactile excellence, build quality, and acoustic refinement. While the original Extended Keyboard's Orange Alps switches achieved legendary status among enthusiasts, the AEK II's Cream damped switches proved more practical for professional environments where the keyboard found widespread adoption.

See Also

• Apple Extended Keyboard
• AppleDesign Keyboard
• Apple Desktop Bus
• Macintosh IIsi