Macintosh LC 575
 | |
| Macintosh LC 575 | |
| Specifications | |
|---|---|
| Manufacturer | Apple Computer, Inc. |
| Type | All-in-one Personal Computer |
| Released | February 2, 1994 |
| Discontinued | April 3, 1995 |
| Intro price | US$1,699 (education market) |
| CPU | Motorola 68LC040 @ 33 MHz (66 MHz bus) |
| Memory | 4 MB or 5 MB RAM (expandable to 36 MB) |
| Storage | 160 MB or 320 MB SCSI hard drive, 2X CD-ROM drive |
| Display | 14" Sony Trinitron color CRT (640×480 pixels) |
| Sound | Stereo 16-bit, 44.1 kHz |
| Dimensions | 16.5" H × 13.2" W × 16.25" D (419 × 335 × 413 mm) |
| Weight | 38.4 lbs (17.4 kg) |
| OS / Firmware | System 7.1.1 – Mac OS 8.1 |
| Predecessor | Macintosh LC 550 |
| Successor | Macintosh LC 580 |
| Codename | Optimus |
| Model no. | M1347 |
The Macintosh LC 575 was an all-in-one personal computer introduced on February 2, 1994, as the third model in Apple's LC 500 series. The LC 575 combined a 33 MHz Motorola 68LC040 processor with a built-in 14-inch Sony Trinitron color display, representing a significant performance upgrade from its 68030-based predecessors. The machine introduced Apple's Communication Slot (Comm Slot), a proprietary expansion interface for network and modem cards.
Model Variants
[edit | edit source]The LC 575 was sold primarily to educational institutions, while consumer versions were marketed under the Performa brand with varying specifications:
Education Models
[edit | edit source]- Macintosh LC 575 – 5 MB RAM, 160 MB hard drive, 2X CD-ROM drive (standard configuration)
- Macintosh LC 575 – 4 MB RAM, no CD-ROM drive (budget configuration for volume purchases)
- Macintosh LC 575 – 8 MB RAM, 320 MB hard drive (available for volume purchases)
Consumer Models (Performa)
[edit | edit source]- Macintosh Performa 575 – 5 MB RAM, 250 MB hard drive, 2X CD-ROM, internal modem
- Macintosh Performa 577 – 5 MB RAM, 320 MB hard drive, 2X CD-ROM, internal modem
- Macintosh Performa 578 – 8 MB RAM, 320 MB hard drive, 2X CD-ROM, internal modem
Performa models included bundled software packages with ClarisWorks 2.0, Quicken 4.0, Grolier's Encyclopedia, and educational titles. Units shipped with System 7.1.1 and System Enabler 065 (later Enabler 364).
General Maintenance
[edit | edit source]Cleaning procedures, capacitor inspection, and preventive care specific to the LC 575's all-in-one design are documented in Macintosh LC 575 General Maintenance.
PCB Schematics & Service Manual
[edit | edit source]The LC 575 uses a modified Quadra 605 logic board adapted for the LC 500 series chassis with integrated video circuitry. The system consists of:
Logic Board
[edit | edit source]The logic board shares architecture with the Macintosh LC 475 and Macintosh Quadra 605, featuring:
- Motorola 68LC040 processor at 33 MHz (can be upgraded with full 68040 with FPU)
- Custom VLSI chips for memory management and I/O control
- Integrated video controller with separate VRAM
Analog Board
[edit | edit source]The analog board provides power regulation and CRT drive circuits for the 14" Trinitron display, shared with LC 520/550 models but with updated components for the 575's requirements.
Apple Service Manual
[edit | edit source]
Service documentation available on the Apple Service Source page.
Schematic
[edit | edit source]
Download the Macintosh LC 575 Schematic here: File:LC575.pdf
Capacitor Replacement Guide
[edit | edit source]Surface-mount electrolytic capacitors on the LC 575 logic board require replacement due to age-related leakage. Specifications and procedures are documented on the Macintosh LC 575 Capacitor Replacement Guide page.
Retrobrite
[edit | edit source]The LC 575's beige plastics yellow from UV exposure and bromine flame retardants. Restoration techniques are detailed on the Retrobrite page.
Troubleshooting
[edit | edit source]Common issues including power supply failures, CRT problems, and capacitor-related failures are covered in the Macintosh LC 575 Troubleshooting guide.
Technical Details
[edit | edit source]System Architecture
[edit | edit source]| Sub-system | Specification (Macintosh LC 575, February 1994) |
|---|---|
| CPU | Motorola 68LC040 @ 33 MHz (66 MHz clock, divided by 2) |
| Bus width | 32-bit data • 32-bit address (4 GB addressable space) |
| ROM | 1 MB ROM – System 7.1 ROM with 68040 support |
| RAM | 4 MB soldered (expandable to 36 MB via single 72-pin SIMM) |
| L1 Cache | 8 KB unified instruction/data cache (on-chip) |
| Video | 640 × 480 color (14" Sony Trinitron) • 512 KB VRAM standard (1 MB max) |
| Color depth | 256 colors (8-bit) at 512 KB VRAM • 32,768 colors (16-bit) at 1 MB VRAM |
| Sound | Stereo 16-bit sound • 44.1 kHz sample rate • Built-in stereo speakers |
| Storage | 1.44 MB SuperDrive • 160-320 MB SCSI hard drive • 2X CD-ROM (optional) |
| I/O Ports | ADB × 1 • DB-25 SCSI • Mini-DIN-8 serial × 2 • Microphone • Headphone |
| Expansion | LC PDS + Comm Slot (first Mac with Communication Slot) |
Memory Configuration
[edit | edit source]| Configuration | Soldered RAM | SIMM Slot | Total RAM |
|---|---|---|---|
| Minimum | 4 MB | Empty | 4 MB |
| Standard (LC 575) | 4 MB | 1 MB | 5 MB |
| Upgraded | 4 MB | 4 MB | 8 MB |
| Enhanced | 4 MB | 8 MB | 12 MB |
| High-end | 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, 32 MB modules
- Single-banked 64 MB SIMMs work but double-banked do not
- Installation requires partial disassembly of the computer
Built-in Display Specifications
[edit | edit source]| Parameter | Specification |
|---|---|
| Display Type | Sony Trinitron aperture grille CRT |
| Screen Size | 14" diagonal (12.4" viewable) |
| Resolution | 640 × 480 pixels native |
| Alternate Mode | 560 × 384 pixels (Apple IIe Card compatibility) |
| Refresh Rate | 66.67 Hz |
| Dot Pitch | 0.28mm aperture grille |
| VRAM | 512 KB standard (256 colors) • 1 MB maximum (32,768 colors) |
The Trinitron tube provides superior color reproduction and brightness compared to shadow mask CRTs, though characteristic horizontal stabilization wires are visible across the screen.
Communication Slot (Comm Slot)
[edit | edit source]The LC 575 was the first Macintosh to feature the Communication Slot, a proprietary expansion interface designed for networking and modem cards.
Comm Slot Specifications:
- Based on LC PDS architecture
- 68030-compatible bus interface
- Shares serial lines with external modem port
- Notch positioned toward rear of slot
- Disables external modem port when card installed
Compatible Comm Slot Cards:
- Apple Ethernet CS Twisted Pair (10BASE-T) – Part M3065Z/A
- Apple Ethernet CS Thin Coax (10BASE2) – Part M2708Z/A
- Macintosh Express Fax/Modem (14.4 kbps) – Part M2480LL/A
- Farallon EtherMac LC Card (10BASE-T) – Part YPN598
- Various third-party modem cards (14.4-28.8 kbps)
LC PDS (Processor Direct Slot)
[edit | edit source]In addition to the Comm Slot, the LC 575 retains the standard LC PDS for expansion:
LC PDS Specifications:
- 114-pin connector (backward compatible with 96-pin LC cards)
- Direct 68040 bus access
- Supports LC II and LC III expansion cards
Common PDS Cards:
- Apple IIe Card – Apple II emulation
- PowerPC Upgrade Card – 50-100 MHz PowerPC 601
- Video capture cards – Various manufacturers
- Accelerator cards – 68040 and PowerPC upgrades
PowerPC Upgrade Path
[edit | edit source]Apple offered the Macintosh Processor Upgrade Card (November 1994 - March 1996) providing:
- PowerPC 601 processor at 50 MHz (Apple) or 100 MHz (third-party)
- Plugs into LC PDS slot
- Enables Mac OS 8.5-9.1 support
- Maintains 68040 emulation for compatibility
Third-party upgrades from DayStar Digital and Sonnet offered enhanced specifications with faster processors and additional cache.
Custom Chips & Controllers
[edit | edit source]| Chip | Function | Details |
|---|---|---|
| 68LC040 | Main CPU | 33 MHz, no FPU (can be upgraded to full 68040) |
| SWIM II | Floppy controller | Supports 400K, 800K, 1.44 MB disks |
| NCR 53C96 | SCSI controller | 8-bit asynchronous SCSI, 5 MB/s maximum |
| Z85C30 SCC | Serial controller | Dual-channel RS-422/RS-232 |
| CUDA | ADB/Power management | Handles ADB, power control, PRAM |
| AWACS | Audio controller | 16-bit stereo sound generation |
I/O Ports & Connectivity
[edit | edit source]| Port | Type | Function | Notes |
|---|---|---|---|
| ADB | Mini-DIN-4 | Keyboard/Mouse | Single port (daisy-chain capable) |
| Serial (Modem) | Mini-DIN-8 | RS-422/RS-232 | Disabled when Comm Slot modem installed |
| Serial (Printer) | Mini-DIN-8 | RS-422/LocalTalk | AppleTalk networking capable |
| SCSI | DB-25 | External SCSI | Requires termination for external devices |
| Audio In | 3.5mm jack | Microphone | PlainTalk compatible |
| Audio Out | 3.5mm jack | Headphones/Speakers | Stereo output |
Power Specifications
[edit | edit source]- Input: 100-120V AC or 220-240V AC, 50-60 Hz
- Power consumption: 120W typical, 150W maximum
- Internal voltages: +5V, +12V, -12V (logic) • High voltage for CRT
Environmental Specifications
[edit | edit source]- Operating temperature: 10°C to 35°C (50°F to 95°F)
- Storage temperature: -40°C to 47°C (-40°F to 116.6°F)
- Relative humidity: 20% to 80% non-condensing
Software Compatibility
[edit | edit source]Operating System Support
[edit | edit source]- Minimum: System 7.1.1 with System Enabler 065
- Recommended: System 7.5.5 or Mac OS 7.6.1
- Maximum (68040): Mac OS 8.1
- Maximum (with PowerPC upgrade): Mac OS 9.1
System Enablers Required
[edit | edit source]- System Enabler 065 (original)
- System Enabler 364 (updated)
- Not required with System 7.5 and later
Historical Context
[edit | edit source]The LC 575 represented several technical transitions for Apple:
- Architecture migration – Shifted from 68030 (LC 520/550) to 68040 architecture
- Performance positioning – Provided Quadra-level performance at LC pricing
- Expansion innovation – Introduced Communication Slot standard used through 1997
- Education focus – Maintained Apple's education market dominance
- All-in-one refinement – Improved upon LC 520 design with better integration
Production ceased in April 1995 when the LC 575 was replaced by the Macintosh LC 580, which used a redesigned logic board with IDE instead of SCSI.
Known Issues & Quirks
[edit | edit source]Logic Board Issues
[edit | edit source]- SMD capacitor leakage – Surface-mount capacitors leak electrolyte causing trace damage
- PRAM battery corrosion – Leaking batteries damage nearby components
- Memory SIMM compatibility – Double-banked 64 MB SIMMs cause crashes
- Heat buildup – Limited ventilation in all-in-one design causes component stress
Display & Analog Board
[edit | edit source]- Trinitron stabilization wires – Two horizontal lines visible across screen (normal)
- Geometry drift – Magnetic fields affect display alignment over time
- Analog board capacitors – Age-related failures cause display instability
- Flyback transformer – High-voltage section prone to failure after extended use
Compatibility Considerations
[edit | edit source]- "Mystic" upgrade – LC 575 board popular for Color Classic upgrades
- Clock confusion – Often listed as 66 MHz due to bus speed, CPU runs at 33 MHz
- FPU requirement – Some software requires full 68040, not LC version
- SCSI termination – Internal devices often improperly terminated
Maintenance Resources
[edit | edit source]- Macintosh LC 575 General Maintenance – Regular cleaning and care
- Macintosh LC 575 Capacitor Replacement Guide – SMD capacitor specifications
- Macintosh LC 575 Troubleshooting – Diagnostic procedures
- CRT Discharge Procedure – Safety for internal work
- Macintosh Communication Slot – Expansion card information
Related Pages
[edit | edit source]- Macintosh LC 520 – First LC 500 series model
- Macintosh LC 550 – Direct predecessor
- Macintosh LC 580 – Direct successor
- Macintosh Quadra 605 – Logic board donor
- Macintosh Color Classic – Popular upgrade recipient