Macintosh LC 520

The Macintosh LC 520 was introduced on June 28, 1993, as Apple's first all-in-one LC series computer, departing from the "pizza box" form factor of previous LC models. The LC 520 combined a 14-inch Sony Trinitron color monitor, stereo speakers, CD-ROM drive, and logic board based on the Macintosh LC III into a single integrated unit. Sold primarily through educational channels at $1,599, the LC 520 was also available to consumers as the Macintosh Performa 520, though not in the United States.

Macintosh LC 520

Macintosh LC 520
Specifications
Manufacturer	Apple Computer, Inc.
Type	All-in-one personal computer
Released	June 28, 1993
Discontinued	February 2, 1994
Intro price	US$1,599 (education) – $2,000 (retail)
CPU	Motorola 68030 @ 25 MHz
Memory	5 MB RAM (4 MB on-board + 1 MB SIMM) expandable to 36 MB
Storage	80 MB or 160 MB SCSI hard drive, 2X CD-ROM drive (caddy-loading)
Display	Built-in 14" Sony Trinitron CRT (640×480 pixels)
Sound	Stereo speakers, built-in microphone
Dimensions	17.9" H × 13.5" W × 16.5" D (454 × 343 × 419 mm)
Weight	40.5 lbs (18.4 kg)
OS / Firmware	System 7.1 with Enabler 403 – Mac OS 7.6.1
Predecessor	Macintosh LC III (pizza box form factor)
Successor	Macintosh LC 550
Codename	Mongo
Model no.	M1858 (with CD-ROM)

Development History

The LC 520 began as a design project codenamed "Mongo" following the success of the Macintosh Color Classic. Apple's Industrial Design Group (IDg) explored adapting the Color Classic's design language, dubbed "Espresso," for a larger display version with CD-ROM capability. IDg designers strongly disliked the resulting design and shelved the concept permanently.

In 1992, CEO John Sculley demanded a large-screen all-in-one design within six months to complete his market strategy. Against IDg's objections, Apple's engineering team retrieved the shelved design and rushed it into production. IDg's dissatisfaction with the design prompted them to immediately begin work on the redesigned chassis that became the Power Macintosh 5200 series less than two years later.

Model Variants

The LC 520 was available in several configurations during its seven-month production run:

Education Market (LC 520)

• LC 520 Standard – 5 MB RAM, 80 MB hard drive, 2X CD-ROM drive
• LC 520 Enhanced – 5 MB RAM, 160 MB hard drive, 2X CD-ROM drive

Consumer Market (Performa 520)

• Performa 520 – Identical hardware to LC 520 with consumer software bundle
• Not sold in the United States market
• Available in international markets with localized software

The LC 520 required a caddy for CD-ROM discs, unlike the tray-loading drives in later models. All models shipped with System 7.1 and System Enabler 403 pre-installed.

General Maintenance

Cleaning procedures, PRAM battery management, CRT adjustment, and preventive care are documented in Macintosh LC 520 General Maintenance.

PCB Architecture & Service Documentation

The LC 520 uses two primary circuit boards plus the CRT assembly:

Logic Board

The LC 520 logic board (Apple part number 820-0368-A) is essentially identical to the Macintosh LC III, featuring:

• Motorola 68030 processor at 25 MHz with 32-bit data bus
• Optional 68882 FPU socket for floating-point operations
• Enhanced LC PDS slot supporting both 96-pin (LC/LC II) and 114-pin (LC III) expansion cards
• 72-pin SIMM slot for memory expansion

Analog Board

The analog board (part number 630-1120) provides:

• Power regulation for +5V, +12V, -12V rails
• CRT drive circuits for the 14" Trinitron display
• Audio amplification for built-in stereo speakers
• Deflection circuits for display geometry

Apple Service Manual

Complete service documentation is available on the Apple Service Source page.

Capacitor Replacement Guide

Surface-mount electrolytic capacitors on the LC 520 logic board are prone to leakage. Complete specifications and replacement procedures are documented on the Macintosh LC 520 Capacitor Replacement Guide page.

Troubleshooting

Simasimac patterns, startup failures, CD-ROM issues, and display problems are covered in the Macintosh LC 520 Troubleshooting guide.

Technical Details

System Architecture

Sub-system	Specification (Macintosh LC 520, June 1993)
CPU	Motorola 68030 @ 25 MHz • 32-bit data bus • 24-bit address (16 MB space)
Bus width	32-bit data • 24-bit address • Full 68030 performance (unlike LC/LC II)
ROM	1 MB ROM (2 × 256K × 16-bit chips) • QuickDraw, ADB, SCSI Manager
RAM	4 MB on-board + 1 MB SIMM standard • expandable to 36 MB (72-pin SIMM)
Video	512 KB VRAM standard • 640 × 480 at 8-bit color • expandable to 768 KB VRAM
Sound	Stereo speakers • Built-in microphone • 8-bit 22.254 kHz sampling
Storage	80 or 160 MB SCSI hard drive • 2× CD-ROM (caddy-loading, 300 KB/s)
I/O Ports	ADB × 2 • Mini-DIN-8 serial × 2 • DB-25 SCSI • 3.5mm audio in/out
Expansion	Enhanced LC PDS – 114-pin connector, backward compatible with 96-pin cards

Memory Configuration

RAM Expansion Options

Configuration	On-board	SIMM Size	Total RAM
Minimum	4 MB	None	4 MB
Standard	4 MB	1 MB	5 MB
	4 MB	2 MB	6 MB
	4 MB	4 MB	8 MB
	4 MB	8 MB	12 MB
	4 MB	16 MB	20 MB
Maximum	4 MB	32 MB	36 MB

SIMM Requirements: 72-pin, 80ns or faster, supports 1, 2, 4, 8, 16, or 32 MB modules

Video Specifications

Display Capabilities

VRAM	Resolution	Color Depth	Colors
512 KB	640 × 480	8-bit	256 colors
768 KB	640 × 480	16-bit	Thousands of colors
512 KB	560 × 384	4-bit	16 colors (Apple IIe Card mode)

The 14-inch Sony Trinitron CRT provides:

• 0.26mm dot pitch
• Maximum 640 × 480 resolution
• 60 Hz refresh rate
• Integrated degaussing coil

Enhanced LC PDS Specifications

The LC 520 introduced the enhanced LC PDS slot with 114 pins, maintaining backward compatibility with 96-pin cards from earlier LC models.

Compatible expansion cards:

• Apple IIe Card – Apple II emulation with Y-cable for 5.25" drive support
• Ethernet cards – Various 10BASE-T and AAUI options from Apple, Asante, Farallon
• Video cards – External monitor support (rare)
• Accelerator cards – DayStar PowerCache upgrades

PDS Technical Details:

• Direct connection to 68030 processor bus
• 25 MHz synchronous operation
• 32-bit data path (16-bit compatible mode for older cards)
• Three interrupt lines (IPL0-IPL2)
• +5V and +12V power available

FPU Compatibility

The LC 520 includes an empty socket for a Motorola 68882 FPU operating at 25 MHz. Installation considerations:

• FPU socket on motherboard can be populated with 68882
• Some PDS Ethernet cards include FPU sockets
• Running FPU on both motherboard and PDS card simultaneously is not recommended
• FPU provides significant acceleration for scientific and graphics applications

Storage Subsystem

SCSI Hard Drive

• Interface: 50-pin internal SCSI-1
• Controller: NCR 5380 or compatible
• Transfer rate: Up to 5 MB/s (asynchronous)
• Capacities: 80 MB or 160 MB standard configurations
• Common drives: Quantum ProDrive LPS, Connor CP30084

CD-ROM Drive

• Speed: 2× (300 KB/s)
• Type: Caddy-loading mechanism
• Interface: Internal SCSI (ID 3 typical)
• Format support: ISO 9660, HFS, Audio CD, Photo CD (with software)
• Mechanism: Sony CDU-541 or compatible

Floppy Drive

• Type: Sony MPF-75W SuperDrive
• Capacity: 1.44 MB high-density, 800 KB double-density, 400 KB single-density
• Controller: SWIM chip
• Location: Front-loading, manual inject

Audio System

The LC 520 featured enhanced audio capabilities compared to pizza-box LC models:

• Stereo speakers integrated into case sides
• Built-in microphone (omnidirectional electret)
• Sound input: 22.254 kHz sampling, 8-bit
• Sound output: Stereo, 8-bit DAC
• Audio ports: 3.5mm stereo output, 3.5mm mono input

Power Specifications

• Input: 100-240V AC, 50-60 Hz (auto-switching)
• Power consumption: 150W typical, 200W maximum
• Internal voltages: +5V (logic), +12V (drives), -12V (serial), high voltage for CRT

Logic Board Capacitor List

The LC 520 logic board contains nine surface-mount electrolytic capacitors requiring replacement:

LC 520 Logic Board Capacitors

Quantity	Value	Voltage
2	100 µF	6.3V
6	47 µF	16V
1	10 µF	50V

Tantalum replacements are recommended for longevity. See Macintosh LC 520 Capacitor Replacement Guide for detailed procedures.

Known Issues & Solutions

Common Failures

• Capacitor leakage – Logic board capacitors leak, damaging traces
• PRAM battery corrosion – 3.6V lithium battery damages nearby components
• CD-ROM drive failure – Caddy mechanism prone to mechanical issues
• CRT convergence drift – Degaussing coil or yoke adjustment needed
• Analog board failures – Solder joint cracks near flyback transformer

Upgrade Paths

• LC 550 upgrade – 33 MHz 68030, faster performance
• LC 575 upgrade – 33 MHz 68LC040, significantly faster
• PowerPC upgrade cards – Various third-party PDS solutions

Historical Context

The LC 520 occupied a unique position in Apple's lineup:

• First LC series computer with integrated monitor
• First Macintosh with built-in CD-ROM drive as standard
• Priced at $1,599 for education, competing directly with multimedia PCs
• Short seven-month production run before LC 550 replacement
• Estimated 200,000 units sold primarily to schools

Peter Lewis of The New York Times praised the LC 520's $1,599 price as "perhaps the best value in the entire Macintosh product line," noting it would be difficult to configure a comparable Windows PC for the same price. The 40.5-pound weight made it impractical for teachers to carry home, addressing security concerns in schools.

Design Legacy

Despite IDg's objections to the design, the LC 520 case served as the foundation for:

• Macintosh LC 550 – Direct successor with 33 MHz processor
• Macintosh LC 575 – 68LC040 upgrade with IDE storage
• Macintosh LC 580 – Final 68k model in series
• Macintosh TV – Black variant with TV tuner functionality
• Power Macintosh 5200 series – PowerPC-based successors

The form factor proved popular in education markets through the mid-1990s, with over 2 million units sold across all variants.

Maintenance Resources

• Macintosh LC 520 General Maintenance – Cleaning and preventive care
• Macintosh LC 520 Capacitor Replacement Guide – Complete capacitor specifications
• Macintosh LC 520 Troubleshooting – Diagnostic procedures
• CRT Discharge Procedure – Safety for internal work
• Macintosh Floppy Drive Maintenance – SuperDrive service

Related Pages

• Macintosh LC III – Logic board donor/equivalent
• Macintosh LC 550 – Direct successor
• Macintosh LC 575 – 68040-based upgrade
• Macintosh Color Classic – Compact all-in-one contemporary
• Macintosh Performa 520 – Consumer variant