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{{Infobox computer peripheral
{{Infobox computer peripheral
| name        = Apple Desktop Bus Keyboard
| name        = Apple Desktop Bus Keyboard
| image        = [[File:Apple Desktop Bus Keybaord.jpg|250px]]
| image        = [[File:Apple Desktop Bus Keybaord.jpg|260px|frameless]]
| caption      = Apple Desktop Bus Keyboard with Alps SKCM Orange switches
| caption      = Apple Desktop Bus Keyboard
| manufacturer = Apple Computer, Inc.
| manufacturer = Apple Computer, Inc. (made by Alps Electric and SMK)
| type        = Computer keyboard
| type        = Computer keyboard
| release date = September 15, 1986
| release_date = September 1986 (with the [[Apple IIGS]])
| discontinued = 1992
| price        = US$129 (retail, keyboard only)
| interface    = [[Apple Desktop Bus]]
| interface    = [[Apple Desktop Bus]]
| compatible  = Apple IIGS, all ADB-equipped Macs
| compatible  = Apple IIGS and ADB-equipped Macintosh computers
| dimensions  = 440 mm W × 140 mm D × 42 mm H (rear)
| successor    = [[Apple Keyboard (M0116)]]
| weight      = 0.91 kg (2.0 lbs)
| model        = A9M0330 (part number 658-4081 on early Alps units)
| predecessor  = [[Apple IIe Keyboard]] (A2M2003)
| successor    = [[Apple Keyboard (M0116)]] (M0116)
| model        = A9M0330, 658-4081
}}
}}
<templatestyles src="Template:StyledTable/styles.css" />
The '''Apple Desktop Bus Keyboard''' was sold with the [[Apple IIGS]], and so is often called the Apple IIGS Keyboard. The IIGS and its keyboard were the first Apple products with the [[Apple Desktop Bus]], including a second port on the keyboard for daisy-chaining the [[Apple Desktop Bus Mouse]], the first with a power key, and the first in the "Platinum" design. Deskthority gives the production years as 1986-1992.<ref name="dt">Deskthority wiki, [https://deskthority.net/wiki/Apple_Desktop_Bus_Keyboard "Apple Desktop Bus Keyboard"]: model A9M0330, part number 658-4081 (older Alps version), FCC IDs BCG47FA9M0330 (SMK) and BCG5ARA9M0330 (newer Alps), Alps SKCM Orange and Salmon and SMK Alps-mount switches, Alps SKCL Lock for Caps Lock, production 1986-1992, controller date codes, and photographs of each version. Community wiki, secondary source. Retrieved 2026-09-30.</ref> On the IIGS the power key does not switch the computer on or off: pressed with Control and Command it resets the machine. The ADB microcontroller treats Control-Command-Reset as a special key code, halts the running program and restarts the computer.<ref name="dt" /><ref name="gshw">Apple Computer, ''Apple IIGS Hardware Reference'', 2nd edition (1989), chapter 6, "The Apple Desktop Bus", pp. 124-127. Hosted as [[:File:Apple IIGS Hardware Reference 1989.pdf]].</ref>


The '''Apple Desktop Bus Keyboard''' was the first keyboard to implement Apple's new [[Apple Desktop Bus]] interface, introduced alongside the [[Apple IIGS]] computer on September 15, 1986. Often referred to as the '''Apple IIGS Keyboard''', it pioneered several Apple firsts: the ADB interface, dual ADB ports for daisy-chaining, an integrated power button, and the introduction of the Snow White design language. The keyboard was manufactured in two distinct variants—one in Japan with Alps switches and another in Taiwan with SMK switches—both sharing the same external appearance but differing significantly in internal construction and keycap manufacturing methods.
Apple's IIGS hardware reference describes the keyboard's behaviour: automatic key repeat with rate and delay set from the Control Panel, n-key rollover for the modifier keys, and two-key lockout for the alphanumeric keys, so a third key pressed at the same time as two others is not recognised.<ref name="gshw" />


== Historical Context ==
== Variants ==
The keyboard was made by Alps in Japan and by SMK in Taiwan, with different switches.<ref name="dt" />


The Apple Desktop Bus Keyboard represented a convergence of Apple's computer lines, bridging the Apple II and future Macintosh families. Developed during 1985-1986 as part of the Apple IIGS project, it embodied Apple's vision for a unified peripheral ecosystem. The keyboard introduced the ADB interface months before it appeared on any Macintosh computer, establishing the protocol that would serve Apple for the next thirteen years.
{| class="wikitable styled-table" style="width:95%;"
 
|+'''Apple Desktop Bus Keyboard versions'''<ref name="dt" />
The keyboard's design marked Apple's first implementation of the Snow White design language developed by Hartmut Esslinger's Frog Design team. The introduction of "Platinum" gray coloring on the IIGS and its peripherals established the color scheme that would define Apple products through the 1990s. This represented a significant departure from the beige computers of the early 1980s, positioning Apple as a design-focused company.
! Version !! Rear label !! Switches !! Notes
 
== Design Features ==
 
=== Physical Design ===
The keyboard embodied the Snow White design language principles:
* '''Horizontal grooves:''' Decorative lines creating visual texture
* '''Slanted profile:''' Front-to-back angle for ergonomic typing
* '''Platinum coloring:''' Warm gray tone (Pantone 423C equivalent)
* '''Unified aesthetic:''' Matched Apple IIGS system unit design
 
The 81-key layout represented a transitional design, incorporating elements from both Apple II and Macintosh keyboard traditions:
* '''Escape key:''' First appearance on an Apple keyboard
* '''Control key:''' Positioned left of 'A' (Apple II tradition)
* '''Command keys:''' Open and closed Apple logos
* '''Option key:''' Introduced for special characters
* '''Power button:''' Upper right corner position
 
=== Layout Peculiarities ===
Several non-standard key arrangements distinguished this keyboard:
* '''Arrow keys:''' Single row arrangement (← → ↓ ↑)
* '''Tilde/Grave:''' Positioned left of spacebar
* '''Caps Lock:''' Lower left corner placement
* '''Delete key:''' Labeled as "Delete" (not Backspace)
* '''Return key:''' Backward L-shape configuration
 
== Manufacturing Variants ==
 
=== Japan Variant (658-4081) ===
 
'''Production Period:''' 1986-1991
 
'''Identification:'''
* Label marked "Made in Japan"
* Part number 658-4081 or 825-1301-A
* Early units: Simple rear label
* Later units: A9M0330 designation added
 
'''Switch Technology:'''
* '''Early production (1986-1989):''' Alps SKCM Orange
  * Orange-colored sliders
  * Tactile, non-clicky operation
  * 70g actuation force
* '''Late production (1989-1991):''' Alps SKCM Salmon
  * Pink-salmon colored sliders
  * Identical feel to Orange
  * Slightly different internal construction
 
'''Keycaps:'''
* Material: PBT plastic (except spacebar: ABS)
* Manufacturing: Dye sublimation
* Color: Uniform platinum gray
* Profile: Apple standard (similar to Cherry)
* Stabilizers: Brown Alps-type clips
 
'''Construction Details:'''
* Internal plate: Steel, painted
* PCB: Single-sided with jumper wires
* Controller: Custom Apple ASIC
* Assembly: Three screws with washers
 
=== Taiwan Variant (A9M0330) ===
 
'''Production Period:''' 1987-1992
 
'''Identification:'''
* Label marked "Made in Taiwan"
* Model number A9M0330 prominently displayed
* Consistent labeling throughout production
 
'''Switch Technology:'''
* '''SMK second-generation Alps mount'''
** White-colored sliders
** Tactile, non-clicky operation
** 65g actuation force (lighter than Alps)
** Cross-mount compatible with Alps keycaps
'''Keycaps:'''
* Material: ABS plastic
* Manufacturing: Double-shot injection molding
* Color: Slightly darker gray than Japan variant
* Bottom: Dark gray (two-tone appearance)
* Stabilizers: White SMK-type clips
 
'''Construction Details:'''
* PCB: Includes EMI shielding (tin foil layer)
* Part number: SMK 2J-M9020-02B
* Controller: Socketed ROM chip (341-0124)
* Assembly: Three screws (washers optional)
 
== Technical Specifications ==
 
=== Physical Specifications ===
* '''Dimensions:''' 440mm × 140mm × 42mm
* '''Weight:''' 0.91kg (Japan) / 0.86kg (Taiwan)
* '''Cable:''' Coiled ADB, 1.2m extended
* '''Keys''' 81 total
* '''Typing angle''' 6 degrees
 
=== Electrical Specifications ===
* '''Interface''' Apple Desktop Bus (ADB)
* '''Power consumption''' 25mA typical, 50mA maximum
* '''Operating voltage''' 4.75V - 5.25V
* '''Data rate''' 10 kbit/s maximum
 
=== ADB Protocol Implementation ===
* '''Device type''' Keyboard
* '''Default address''' $2
* '''Handler ID''' $01 (Standard protocol)
* '''Registers'''
** Register 0: Key event data (2 bytes)
** Register 1: Reserved
** Register 2: LED status and modifiers
** Register 3: Device ID and address
=== Key Matrix ===
* '''Matrix size''' 8×11
* '''Rollover''' 2-key guaranteed
* '''Ghosting prevention''' Diode per switch
* '''Debounce''' Hardware (5ms)
 
== Switch Specifications ==
 
=== Alps SKCM Orange/Salmon ===
'''Specifications'''
* Type: Tactile, non-clicky
* Actuation force: 70g ± 10g
* Pre-travel: 2.0mm
* Total travel: 3.5mm
* Lifespan: 10 million actuations
 
'''Characteristics'''
* Smooth tactile bump
* Minimal wobble
* Consistent feel across keyboard
* Self-cleaning contacts
 
=== SMK Second Generation ===
'''Specifications'''
* Type: Tactile, non-clicky
* Actuation force: 65g ± 10g
* Pre-travel: 2.0mm
* Total travel: 3.5mm
* Lifespan: 20 million actuations
 
'''Characteristics'''
* Lighter than Alps
* More pronounced tactility
* Slightly scratchier feel
* Cross-mount Alps compatible
 
=== Alps SKCL Lock (Caps Lock) ===
All variants used the Alps SKCL Lock switch:
* Mechanical latching mechanism
* Physical lock when engaged
* Cream or white housing
* Not user-replaceable with standard switch
 
== Production Information ==
 
=== Serial Number Format ===
'''Japan (658-4081)'''
* Format: NNNNNN (six digits)
* Example: 380504, 318537
 
'''Taiwan (A9M0330)'''
* Format: PPYWWNNNNNN
* PP: Production facility
* Y: Year (7=1987, 8=1988, etc.)
* WW: Week number
* NNNNNN: Sequential number
 
=== Production Timeline ===
* '''1986''' Initial release with Apple IIGS (Japan only)
* '''1987''' Taiwan production begins
* '''1989''' Transition from Orange to Salmon Alps (Japan)
* '''1990''' Peak production year
* '''1991''' Japan production ends
* '''1992''' Final units produced (Taiwan)
 
=== Manufacturing Differences ===
 
{| class="wikitable" style="width:85%; text-align:center;"
|+'''Component Comparison'''
! Component !! Japan Variant !! Taiwan Variant
|-
| Switches || Alps SKCM Orange/Salmon || SMK Second Generation
|-
| Keycaps || PBT, dye-sublimated || ABS, double-shot
|-
| Stabilizers || Brown Alps clips || White SMK clips
|-
|-
| PCB || No shielding || EMI foil shielding
| Alps (Japan), earlier || part number 658-4081 || Alps SKCM Orange || Caps Lock is an Alps SKCL Lock; cream on one orange example
|-
|-
| ROM || Soldered or socketed || Always socketed
| Alps (Japan), later || model A9M0330, FCC ID BCG5ARA9M0330 || Alps SKCM Salmon (apparently) || the later label matches the SMK version; the link to salmon switches is Deskthority's speculation
|-
|-
| Assembly || Screws with washers || Screws, washers optional
| SMK (Taiwan) || model A9M0330, FCC ID BCG47FA9M0330 || white tactile SMK Alps-mount || PCB part number 2J-M9020-02B; double-shot keycaps, slightly darker than the Alps version
|-
| Weight || 0.91kg || 0.86kg
|-
| Production || 1986-1991 || 1987-1992
|}
|}


== Keycap Design ==
Photographed controller date codes are 8844 on an SMK example and 9041 on a salmon Alps example. Deskthority suggests the change to salmon switches may coincide with orange Alps switches going out of production around 1991.<ref name="dt" /> It also infers from the way the parts yellow that the case and space bar are ABS and the other keycaps a different plastic, possibly PBT.<ref name="dt" />


=== Row Profiles ===
== ADB ==
The keyboard used different stem heights for each row:
The keyboard is an encoded ADB device; keyboards default to ADB address $02.<ref name="g318">Apple Computer, ''Guide to the Macintosh Family Hardware'', 2nd edition (1990), chapter 8, Table 8-16, p. 318. Hosted as [[:File:Apple Guide to the Macintosh Family Hardware 2nd Edition 1990.pdf]].</ref> On the IIGS, all input devices on the ADB are controlled by the ADB microcontroller, an M50740 with 96 bytes of RAM and 3K of ROM, and Apple II programs read the keyboard through the Keyboard Data register at $C000.<ref name="gshw" /> The ADB connector carries the data line on pin 1, pulled up to +5 V through a 470 Ω resistor on the computer's logic board; POWER.ON on pin 2 (on the Macintosh II family a key on the ADB keyboard grounds it to pin 4 to switch the power supply on; on other models it is not connected); +5 V on pin 3; and ground on pin 4.<ref name="g288">''Guide to the Macintosh Family Hardware'', 2nd ed., Table 8-1, p. 288.</ref> All ADB devices together may draw no more than 500 mA, and Apple does not recommend daisy-chaining more than three devices on one port.<ref name="g292">''Guide to the Macintosh Family Hardware'', 2nd ed., p. 292.</ref> See [[Apple Desktop Bus]] for the protocol.
* '''Number row''' Tallest stems, switches mounted vertically
* '''QWERTY row''' Standard height
* '''Home row''' Slightly shorter
* '''Bottom row''' Shortest stems
* '''Spacebar''' Custom profile with multiple mount points


=== Typography ===
== Maintenance and repair ==
* '''Font''' Univers 57 Condensed
Both switch types are long out of production, so replacement switches come from donor keyboards.
* '''Style''' Regular (not italic like later Apple keyboards)
* '''Alignment''' Centered on keycap
* '''Special keys''' Icon-based legends (Command, Option)


=== Manufacturing Quality ===
=== Keyboard dead ===
'''Japan variant (dye-sublimation)'''
# Try the keyboard on another ADB machine and with a known-good ADB cable.
* Permanent legends, wear-resistant
# At the computer's ADB port, measure +5 V between pin 3 and pin 4. Pin 1 should idle high through the 470 Ω pull-up.<ref name="g288" />
* Uniform color throughout keycap
# Keep the chain short: no more than three devices on one port.<ref name="g292" />
* PBT resistant to yellowing
* Sharp, precise legends


'''Taiwan variant (double-shot)'''
=== Dead or intermittent key ===
* Legends cannot wear off
# Remove the keycap, flush the switch with isopropyl alcohol while working it, and let it dry fully before testing.
* Two-tone appearance (gray top, dark bottom)
# If that fails, desolder the switch and replace it from a donor of the same version.
* ABS prone to yellowing
* More structural support for stems


== Software Compatibility ==
=== Caps Lock will not latch ===
Caps Lock uses a latching switch (Alps SKCL Lock on the Alps boards), which a standard switch cannot replace.<ref name="dt" />


=== Operating Systems ===
== See also ==
* '''Apple IIGS''' ProDOS 16, GS/OS
* '''Mac OS''' System 3.2 through Mac OS 9.2.2
* '''Apple IIe Card''' Full compatibility
* '''A/UX''' Native support
* '''NeXT''' Limited compatibility
 
=== Key Mapping ===
* '''Open Apple →''' Command
* '''Closed Apple →''' Option
* '''Delete →''' Backspace function
* '''Power key''' Direct system control
 
=== Special Functions ===
* '''Control-Open Apple-Reset''' System reset
* '''Open Apple-Control-Escape''' Programmer's switch
* '''Power button''' Cold boot from off state
 
== Maintenance & Repair ==
 
=== Disassembly ===
 
'''Required tools'''
* Phillips screwdriver #1
* Plastic spudger
* Isopropyl alcohol 90%+
 
'''Procedure'''
# Remove three case screws (note washer presence)
# Separate case halves carefully
# Disconnect cable if removable
# Remove PCB screws
# Lift PCB assembly
 
=== Switch Cleaning ===
 
'''Alps switches'''
# Remove keycap
# Apply isopropyl alcohol drops
# Actuate repeatedly
# Allow complete drying
 
'''SMK switches'''
# Similar process to Alps
# May require disassembly for deep cleaning
# Lubrication not recommended
 
=== Common Problems ===
 
{| class="wikitable" style="width:80%; text-align:center;"
|+'''Troubleshooting Guide'''
! Problem !! Cause !! Solution
|-
| Keys not registering || Dirty switch contacts || Clean with alcohol
|-
| Repeating keys || Worn switch || Replace switch
|-
| ADB not recognized || Cable damage || Test continuity, replace
|-
| Yellowing || UV exposure, age || Retrobright treatment
|-
| Caps Lock stuck || Latch mechanism worn || Replace SKCL switch
|-
| Scratchy feel || Contamination || Disassemble and clean
|}
 
=== Parts Availability ===
* '''Alps switches''' Harvest from donor boards
* '''SMK switches''' Unique to this model
* '''Keycaps''' Not interchangeable between variants
* '''Stabilizers''' Variant-specific
* '''Cable''' Generic ADB cable compatible
 
== Modern Usage ==
 
=== ADB to USB Adapters ===
* '''Griffin iMate''' Original solution (discontinued)
* '''Wombat''' Current best option
* '''TMK converter''' DIY solution
* '''Drakware''' Premium cables
 
=== Compatibility Notes ===
* Power button may not function
* All keys map correctly
* No driver needed for basic function
* Special keys require remapping software
 
=== Restoration ===
 
'''Retrobrighting'''
* More effective on Japan variant (PBT)
* Taiwan variant (ABS) prone to brittleness
* Use hydrogen peroxide method
* Monitor carefully to prevent damage
 
'''Switch restoration'''
* Orange/Salmon Alps highly valued
* Ultrasonic cleaning recommended
* Springs can be replaced
* Slider replacement difficult
 
== Collector Information ==
 
=== Market Value (2024) ===
* '''Japan/Orange Alps''' $200-400
* '''Japan/Salmon Alps''' $150-300
* '''Taiwan/SMK''' $100-200
* '''Mint/boxed''' +100% premium
 
=== Authentication ===
* Verify label format matches variant
* Check switch type with keycap removal
* Confirm keycap manufacturing method
* Inspect stabilizer clip color
 
=== Desirability Factors ===
* Orange Alps most sought after
* Complete original cable important
* Minimal yellowing commands premium
* Original packaging extremely rare
 
== Cultural Impact ==
 
The Apple Desktop Bus Keyboard introduced design and technical elements that influenced Apple's keyboard designs for over a decade. The dual ADB ports established the precedent for keyboard-integrated hubs, while the power button placement became standard on Apple keyboards until the early 2000s.
 
The keyboard's unusual layout, particularly the single-row arrow keys and unconventional modifier key positions, proved controversial. These quirks were quickly addressed in the successor M0116, demonstrating Apple's responsiveness to user feedback while maintaining design innovation.
 
For many users, this was their introduction to mechanical keyboards, with the Alps switches providing a typing experience that many still consider superior to modern alternatives. The keyboard's association with the Apple IIGS, used extensively in schools during the late 1980s and early 1990s, created lasting nostalgic connections for a generation of computer users.
 
== Production Statistics ==
 
Estimated production numbers based on serial number analysis:
* '''Total production''' ~750,000 units
* '''Japan variant''' ~400,000 (53%)
* '''Taiwan variant''' ~350,000 (47%)
* '''Orange Alps''' ~200,000 units
* '''Salmon Alps''' ~200,000 units
* '''SMK switches''' ~350,000 units
 
== Legacy ==
 
The Apple Desktop Bus Keyboard established several precedents:
* First implementation of ADB protocol
* Introduction of Snow White design language
* Established dual-port keyboard design
* Pioneered keyboard power button integration
 
While its non-standard layout was controversial, the build quality and switch technology represented a high point in Apple keyboard construction. The Orange Alps switches in particular have achieved legendary status among keyboard enthusiasts, with these switches commanding premium prices when harvested for custom keyboard projects.
 
The keyboard's role in introducing ADB cannot be understated—this interface would serve Apple computers for thirteen years, making it one of the longest-lived peripheral standards in personal computing history. The backward compatibility maintained throughout the ADB era meant this keyboard could be used with Macintosh systems released a decade after its discontinuation.
 
== See Also ==
* [[Apple Desktop Bus]]
* [[Apple Desktop Bus]]
* [[Apple Desktop Bus Mouse]]
* [[Apple Keyboard (M0116)]]
* [[Apple Extended Keyboard|Apple Extended Keyboard]]
* [[Apple IIGS]]
* [[Apple IIGS]]
* [[Apple Keyboard]] (M0116)
* [[Retrobrite]]
* [[Apple Extended Keyboard]]
 
== References ==
<references />


{{Navbox-AppleVintageAccessories}}
{{Navbox-AppleVintageAccessories|state=collapsed}}


[[Category:Apple Vintage Accessories]]
[[Category:Apple Vintage Accessories]]
[[Category:Apple Desktop Bus]]
[[Category:Apple Desktop Bus]]

Latest revision as of 19:26, 1 October 2026

Apple Desktop Bus Keyboard
Apple Desktop Bus Keyboard
Manufacturer Apple Computer, Inc. (made by Alps Electric and SMK)
Type Computer keyboard
Release date September 1986 (with the Apple IIGS)
Interface Apple Desktop Bus
Compatible Apple IIGS and ADB-equipped Macintosh computers
Successor Apple Keyboard (M0116)
Model A9M0330 (part number 658-4081 on early Alps units)

The Apple Desktop Bus Keyboard was sold with the Apple IIGS, and so is often called the Apple IIGS Keyboard. The IIGS and its keyboard were the first Apple products with the Apple Desktop Bus, including a second port on the keyboard for daisy-chaining the Apple Desktop Bus Mouse, the first with a power key, and the first in the "Platinum" design. Deskthority gives the production years as 1986-1992.[1] On the IIGS the power key does not switch the computer on or off: pressed with Control and Command it resets the machine. The ADB microcontroller treats Control-Command-Reset as a special key code, halts the running program and restarts the computer.[1][2]

Apple's IIGS hardware reference describes the keyboard's behaviour: automatic key repeat with rate and delay set from the Control Panel, n-key rollover for the modifier keys, and two-key lockout for the alphanumeric keys, so a third key pressed at the same time as two others is not recognised.[2]

Variants

[edit | edit source]

The keyboard was made by Alps in Japan and by SMK in Taiwan, with different switches.[1]

Apple Desktop Bus Keyboard versions[1]
Version Rear label Switches Notes
Alps (Japan), earlier part number 658-4081 Alps SKCM Orange Caps Lock is an Alps SKCL Lock; cream on one orange example
Alps (Japan), later model A9M0330, FCC ID BCG5ARA9M0330 Alps SKCM Salmon (apparently) the later label matches the SMK version; the link to salmon switches is Deskthority's speculation
SMK (Taiwan) model A9M0330, FCC ID BCG47FA9M0330 white tactile SMK Alps-mount PCB part number 2J-M9020-02B; double-shot keycaps, slightly darker than the Alps version

Photographed controller date codes are 8844 on an SMK example and 9041 on a salmon Alps example. Deskthority suggests the change to salmon switches may coincide with orange Alps switches going out of production around 1991.[1] It also infers from the way the parts yellow that the case and space bar are ABS and the other keycaps a different plastic, possibly PBT.[1]

ADB

[edit | edit source]

The keyboard is an encoded ADB device; keyboards default to ADB address $02.[3] On the IIGS, all input devices on the ADB are controlled by the ADB microcontroller, an M50740 with 96 bytes of RAM and 3K of ROM, and Apple II programs read the keyboard through the Keyboard Data register at $C000.[2] The ADB connector carries the data line on pin 1, pulled up to +5 V through a 470 Ω resistor on the computer's logic board; POWER.ON on pin 2 (on the Macintosh II family a key on the ADB keyboard grounds it to pin 4 to switch the power supply on; on other models it is not connected); +5 V on pin 3; and ground on pin 4.[4] All ADB devices together may draw no more than 500 mA, and Apple does not recommend daisy-chaining more than three devices on one port.[5] See Apple Desktop Bus for the protocol.

Maintenance and repair

[edit | edit source]

Both switch types are long out of production, so replacement switches come from donor keyboards.

Keyboard dead

[edit | edit source]
  1. Try the keyboard on another ADB machine and with a known-good ADB cable.
  2. At the computer's ADB port, measure +5 V between pin 3 and pin 4. Pin 1 should idle high through the 470 Ω pull-up.[4]
  3. Keep the chain short: no more than three devices on one port.[5]

Dead or intermittent key

[edit | edit source]
  1. Remove the keycap, flush the switch with isopropyl alcohol while working it, and let it dry fully before testing.
  2. If that fails, desolder the switch and replace it from a donor of the same version.

Caps Lock will not latch

[edit | edit source]

Caps Lock uses a latching switch (Alps SKCL Lock on the Alps boards), which a standard switch cannot replace.[1]

See also

[edit | edit source]

References

[edit | edit source]
  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Deskthority wiki, "Apple Desktop Bus Keyboard": model A9M0330, part number 658-4081 (older Alps version), FCC IDs BCG47FA9M0330 (SMK) and BCG5ARA9M0330 (newer Alps), Alps SKCM Orange and Salmon and SMK Alps-mount switches, Alps SKCL Lock for Caps Lock, production 1986-1992, controller date codes, and photographs of each version. Community wiki, secondary source. Retrieved 2026-09-30.
  2. ↑ 2.0 2.1 2.2 Apple Computer, Apple IIGS Hardware Reference, 2nd edition (1989), chapter 6, "The Apple Desktop Bus", pp. 124-127. Hosted as File:Apple IIGS Hardware Reference 1989.pdf.
  3. ↑ Apple Computer, Guide to the Macintosh Family Hardware, 2nd edition (1990), chapter 8, Table 8-16, p. 318. Hosted as File:Apple Guide to the Macintosh Family Hardware 2nd Edition 1990.pdf.
  4. ↑ 4.0 4.1 Guide to the Macintosh Family Hardware, 2nd ed., Table 8-1, p. 288.
  5. ↑ 5.0 5.1 Guide to the Macintosh Family Hardware, 2nd ed., p. 292.


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