Macintosh LC 550
 | |
| Macintosh LC 550 | |
| Specifications | |
|---|---|
| Manufacturer | Apple Computer, Inc. |
| Type | All-in-one personal computer |
| Released | February 2, 1994 |
| Discontinued | March 23, 1995 |
| Intro price | US$1,200 (education) |
| CPU | Motorola 68030 @ 33 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 (tray-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 520 |
| Successor | Macintosh LC 575 |
| Codename | Hook 33 |
| Model no. | M2113 (with CD-ROM) |
The Macintosh LC 550 was introduced on February 2, 1994, as the direct successor to the Macintosh LC 520. The LC 550 increased processor speed from 25 MHz to 33 MHz while maintaining the same all-in-one form factor with integrated 14-inch color display, stereo speakers, and CD-ROM drive. The logic board used in the LC 550 is essentially identical to that of the Macintosh Color Classic II, making it a popular upgrade option for original Color Classic owners. Sold primarily to educational institutions at $1,200, the LC 550 was also available as the Macintosh Performa 550 and Performa 560 "Money Edition" through retail channels.
Development & Market Position
The LC 550, codenamed "Hook 33," addressed the primary criticism of the LC 520: insufficient processing power for multimedia applications. The 33 MHz 68030 processor provided a 32% clock speed increase over its predecessor, while the system bus also increased from 25 MHz to 33 MHz, improving overall system responsiveness.
Released simultaneously with the 68LC040-based Macintosh LC 575, the LC 550 occupied the lower price point in Apple's education lineup. The choice between models allowed schools to balance performance requirements against budget constraints. The LC 550 remained in production for 13 months until March 23, 1995, when the LC 575 became the sole all-in-one offering.
Model Variants
The LC 550 was sold in multiple configurations across education and consumer markets:
Education Market (LC 550)
- LC 550 Standard – 5 MB RAM, 80 MB hard drive, 2X CD-ROM drive
- LC 550 Enhanced – 5 MB RAM, 160 MB hard drive, 2X CD-ROM drive
- LC 550 No CD-ROM – Configuration without optical drive (cost-saving option)
Consumer Market (Performa)
- Performa 550 – 5 MB RAM, 160 MB hard drive, consumer software bundle
- Performa 560 Money Edition – Enhanced business software bundle via Money magazine partnership
The CD-ROM drive in the LC 550 switched from the caddy-loading mechanism of the LC 520 to a tray-loading design, eliminating the need for disc caddies.
General Maintenance
Cleaning procedures, PRAM battery management, CRT adjustment, and preventive care are documented in Macintosh LC 550 General Maintenance.
PCB Architecture & Service Documentation
The LC 550 shares its logic board design with the Color Classic II, using Apple part number 820-0368-A:
Logic Board
The LC 550 logic board features:
- Motorola 68030 processor at 33 MHz with full 32-bit data bus
- Optional 68882 FPU socket for floating-point operations
- Enhanced LC PDS slot supporting both 96-pin and 114-pin expansion cards
- 72-pin SIMM slot for memory expansion up to 36 MB
Analog Board
The analog board provides:
- Power regulation for +5V, +12V, -12V rails
- CRT drive circuits for the 14" Trinitron display
- Audio amplification for stereo speakers
- Deflection circuits for display geometry
Apple Service Manual
Service documentation is available on the Apple Service Source page.
Capacitor Replacement Guide
Surface-mount electrolytic capacitors on the LC 550 logic board require periodic replacement. Specifications and procedures are documented on the Macintosh LC 550 Capacitor Replacement Guide page.
Troubleshooting
Boot failures, display issues, CD-ROM problems, and audio faults are covered in the Macintosh LC 550 Troubleshooting guide.
Technical Details
System Architecture
| Sub-system | Specification (Macintosh LC 550, February 1994) |
|---|---|
| CPU | Motorola 68030 @ 33 MHz • Full 32-bit data bus • Integrated PMMU |
| Bus width | 32-bit data • 24-bit address (16 MB addressable space) |
| ROM | 1 MB ROM (2 × 256K × 16-bit chips) • System 7.1 support |
| 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 (tray-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
The LC 550 uses a single 72-pin SIMM slot for memory expansion beyond the 4 MB soldered to the logic board:
| 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
- Non-parity or parity (parity ignored)
- Supports 1, 2, 4, 8, 16, or 32 MB modules
- Single SIMM only (one slot available)
Video Specifications
The LC 550 provides improved video capabilities over the LC 520:
| 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) |
VRAM Configuration:
- 512 KB VRAM soldered on-board (standard)
- One 68-pin VRAM SIMM slot for expansion
- Add 256 KB VRAM SIMM for 768 KB total
- Maximum 768 KB VRAM (LC 550 specific limitation)
The 14-inch Sony Trinitron CRT specifications:
- 0.26mm dot pitch
- 640 × 480 maximum resolution
- 60 Hz refresh rate (NTSC)
- Integrated degaussing coil
Enhanced LC PDS Specifications
The LC 550 maintains the enhanced 114-pin PDS slot introduced with the LC 520:
Compatible expansion cards:
- Apple IIe Card – Full Apple II emulation with 128 KB RAM
- Ethernet cards – 10BASE-T networking from Apple, Asante, Farallon
- Accelerator cards – Limited options due to 68030 architecture
- Video cards – External monitor support (rare for this model)
PDS Technical Details:
- Direct connection to 68030 processor bus
- 33 MHz synchronous operation (faster than LC 520's 25 MHz)
- 32-bit data path with 16-bit compatibility mode
- Three interrupt lines (IPL0-IPL2)
- +5V and +12V power available
FPU Support
The LC 550 includes an empty socket for optional Motorola 68882 FPU:
- Speed: 33 MHz (matches CPU clock)
- Performance: Significant acceleration for scientific/CAD applications
- Compatibility: Some PDS Ethernet cards include FPU sockets
- Installation: Simple socketed installation, no modifications required
Storage Subsystem
SCSI Hard Drive
- Interface: 50-pin internal SCSI-1
- Controller: NCR 5380 or compatible
- Transfer rate: Up to 5 MB/s theoretical (1.5 MB/s typical)
- Capacities: 80 MB or 160 MB standard
- Common drives: Quantum ProDrive LPS, Connor CP30084
CD-ROM Drive
- Speed: 2× (300 KB/s)
- Type: Tray-loading mechanism (improved from LC 520's caddy system)
- Interface: Internal SCSI (typically ID 3)
- Format support: ISO 9660, HFS, Audio CD, Photo CD
- Mechanism: Sony CDU-561 or Apple-branded equivalent
Floppy Drive
- Type: Sony MPF-75W SuperDrive
- Capacity: 1.44 MB high-density, 800 KB double-density
- Controller: SWIM II chip
- Location: Front-loading, manual inject
Audio System
The LC 550 features enhanced stereo audio:
- Speakers: Stereo phase-shift design integrated into case
- Microphone: Omnidirectional electret built into front bezel
- Sound input: 22.254 kHz sampling, 8-bit
- Sound output: Stereo, 8-bit DAC
- Ports: 3.5mm stereo output, 3.5mm mono input
Power Specifications
- Input: 100-240V AC, 50-60 Hz (auto-switching)
- Consumption: 150W typical, 200W maximum
- Internal voltages: +5V (logic), +12V (drives), -12V (serial), CRT high voltage
Color Classic II Compatibility
The LC 550 logic board's compatibility with the Color Classic creates upgrade opportunities:
Logic Board Swap
The LC 550 logic board (820-0368-A) is identical to the Color Classic II board and can be directly swapped into an original Color Classic chassis. This upgrade provides:
- 33 MHz processor speed (vs 16 MHz)
- 32-bit data bus (vs 16-bit)
- 36 MB maximum RAM (vs 10 MB)
- Enhanced LC PDS slot
VRAM Differences
- Color Classic II: 256 KB base VRAM, expandable to 512 KB
- LC 550: 512 KB base VRAM, expandable to 768 KB
- This difference affects maximum color depth capabilities
Installation Considerations
- No case modifications required
- Original Color Classic rear ports align perfectly
- System identifies as "Color Classic II" after upgrade
- Existing peripherals remain compatible
Logic Board Capacitor List
The LC 550 logic board contains surface-mount electrolytic capacitors requiring replacement:
| Quantity | Value | Voltage | Type |
|---|---|---|---|
| 2 | 100 µF | 6.3V | SMD Electrolytic |
| 6 | 47 µF | 16V | SMD Electrolytic |
| 1 | 10 µF | 50V | SMD Electrolytic |
Tantalum replacements are recommended. See Macintosh LC 550 Capacitor Replacement Guide for procedures.
Known Issues & Solutions
Common Failures
- Capacitor leakage – Surface-mount capacitors leak, damaging traces
- PRAM battery damage – 3.6V lithium battery corrodes nearby components
- CD-ROM tray failure – Mechanical wear on tray-loading mechanism
- Analog board failures – Solder joints crack near flyback transformer
- VRAM socket oxidation – Poor contact causes color issues
Overclock Modification
The LC 550 shares its PCB design with the LC 520, allowing a simple resistor modification on LC 520 boards to achieve 33 MHz operation:
- Remove resistors R67, R75, R79 on LC 520 board
- Board operates at 33 MHz (LC 550/Color Classic II speed)
- No component changes required
- Fully reversible modification
Upgrade Options
- LC 575 logic board – Direct swap for 68LC040 processor upgrade
- PowerPC upgrade cards – Limited PDS options available
- Memory expansion – Up to 32 MB SIMM for 36 MB total
- VRAM upgrade – 256 KB SIMM for enhanced color depth
Historical Context
The LC 550 served as a transitional model in Apple's education strategy:
- Provided cost-effective 33 MHz performance for schools
- Maintained compatibility with existing LC software library
- Offered alongside LC 575 for flexible purchasing options
- Production overlapped with both LC 520 and LC 575
Sales figures indicate approximately 150,000 units sold, primarily to educational institutions. The Performa variants achieved modest retail success, particularly the Performa 560 "Money Edition" which included business software valued at over $1,000.
Design Legacy
The LC 550 represented an incremental refinement of the LC 500 series design:
- Processor speed matched contemporary compact Macs
- Tray-loading CD-ROM improved usability
- Logic board compatibility enabled Color Classic upgrades
- Form factor continued through LC 575 and LC 580
The all-in-one design influenced the later Power Macintosh 5200 series and iMac development, though the bulky CRT-based form factor was ultimately replaced by LCD technology.
Maintenance Resources
- Macintosh LC 550 General Maintenance – Cleaning and preventive care
- Macintosh LC 550 Capacitor Replacement Guide – Complete specifications
- Macintosh LC 550 Troubleshooting – Diagnostic procedures
- CRT Discharge Procedure – Safety for internal work
- Macintosh Floppy Drive Maintenance – SuperDrive service
Related Pages
- Macintosh LC 520 – Direct predecessor
- Macintosh LC 575 – 68040-based successor
- Macintosh Color Classic II – Logic board twin
- Macintosh TV – Black variant with TV functionality
- Macintosh Performa 550 – Consumer variant