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Verified against Apple's LC 520/550/575 Service Source (hosted) and EveryMac. Corrected: dimensions 45.5x34.4x42.0cm not 41.9x33.5x41.3; weight 18.4kg not 17.4; viewable 13in not 12.4; grille pitch 0.26mm not 0.28; max power 120W (the 150W was invented); operating 10-40C not 10-35; storage -40 to 65C not -40 to 47; humidity 20-95% not 20-80; model M1640 not M1347. Removed the '66 MHz bus', the 16-bit/44.1kHz sound claim, the unsourced chip-function and Comm-card part tables, and four red link...
 
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| caption      = Macintosh LC 575
| caption      = Macintosh LC 575
| manufacturer = Apple Computer, Inc.
| manufacturer = Apple Computer, Inc.
| type        = All-in-one Personal Computer
| type        = All-in-one personal computer
| release date = February 2, 1994
| release date = 2 February 1994
| discontinued = April 3, 1995
| discontinued = 3 April 1995
| price        = US$1,699 (education market)
| price        = US$1,700
| cpu          = Motorola 68LC040 @ 33 MHz (66 MHz bus)
| cpu          = Motorola 68LC040 @ 33 MHz
| memory      = 4 MB or 5 MB RAM (expandable to 36 MB)
| memory      = 4 MB on board, expandable to 36 MB
| storage      = 160 MB or 320 MB SCSI hard drive, 2X CD-ROM drive
| storage      = 160 MB or 320 MB SCSI hard drive; manual-insert 1.4 MB SuperDrive; optional 2x CD-ROM
| display      = 14" Sony Trinitron color CRT (640×480 pixels)
| display      = 14 in Trinitron CRT, 13 in viewable, 640 x 480
| sound        = Stereo 16-bit, 44.1 kHz
| sound        = Stereo output, monaural input; 11/22 kHz record, 22 kHz playback
| dimensions  = 16.5" H × 13.2" W × 16.25" D (419 × 335 × 413 mm)
| dimensions  = 45.5 cm H x 34.4 cm W x 42.0 cm D (17.9 x 13.5 x 16.5 in)
| weight      = 38.4 lbs (17.4 kg)
| weight      = 18.4 kg (40.5 lb)
| os          = System 7.1.1 – Mac OS 8.1
| os          = System 7.1 - Mac OS 8.1
| predecessor  = [[Macintosh LC 550]]
| predecessor  = [[Macintosh LC 550]]
| successor    = [[Macintosh LC 580]]
| successor    = [[Macintosh LC 580]]
| codename    = Optimus
| codename    = Optimus
| model        = M1347
| model        = M1640
}}
}}
The '''Macintosh LC 575''' is an all-in-one Macintosh introduced on 2 February 1994 and discontinued on
3 April 1995.<ref name="everymac-575">[https://everymac.com/systems/apple/mac_lc/specs/mac_lc_575.html EveryMac.com — Apple Macintosh LC 575 Specs]. Third-party reference, used here for introduction and discontinuation dates, price, model and Gestalt identifiers, supported system software, and for the explanation of the 66 MHz figure sometimes quoted for this machine.</ref> It is the 68LC040 member of Apple's LC 500 series: the same chassis and the same
14-inch Trinitron display as the [[Macintosh LC 520|LC 520]] and [[Macintosh LC 550|LC 550]], with a
faster processor and one extra expansion slot.


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 [[Macintosh Communication Slot|Communication Slot]] (Comm Slot), a proprietary expansion interface for network and modem cards.
Apple's identifying features for the LC 575, as against the LC 520 and LC 550, are precisely three: a
68LC040 processor, an additional communications slot, and a hook-and-loop-attached
battery.<ref name="ss-520">Apple Computer, ''Service Source: Macintosh LC 520, 550, 575'' — Basics, Specifications, Troubleshooting, Take Apart, Adjustments, Additional Procedures and Exploded View chapters. Hosted on this wiki as [[:File:Lc 520.550.575.pdf]]; see [[Macintosh LC 520/550/575 Service Source]].</ref> The LC 550 and LC 575 also share the newer manual-insert SuperDrive, a revised
chassis harness with no floppy drive adapter, and the caddyless CD 300+ CD-ROM drive.<ref name="ss-520" />


== Model Variants ==
'''On the 66 MHz figure.''' The LC 575 is sometimes listed as a 66 MHz machine. Apple's own
specification gives 33 MHz; the 66 MHz figure is the oscillator feeding the processor, which is
not clock-doubled.<ref name="ss-520" /><ref name="everymac-575" />


The LC 575 was sold primarily to educational institutions, while consumer versions were marketed under the Performa brand with varying specifications:
== Model variants ==


=== Education Models ===
The LC 575 was sold to education. The consumer equivalents are the Performa 575, 577 and 578. Apple's
* '''Macintosh LC 575''' – 5 MB RAM, 160 MB hard drive, 2X CD-ROM drive (standard configuration)
own service documentation for this chassis family covers the LC 520, LC 550 and LC 575 together; the
* '''Macintosh LC 575''' – 4 MB RAM, no CD-ROM drive (budget configuration for volume purchases)
Performa variants are the same machines with different bundles.<ref name="ss-520" />
* '''Macintosh LC 575''' – 8 MB RAM, 320 MB hard drive (available for volume purchases)


=== Consumer Models (Performa) ===
Configurations quoted by Apple's Service Source are a 160 MB or 320 MB SCSI hard drive, with the
* '''Macintosh Performa 575''' – 5 MB RAM, 250 MB hard drive, 2X CD-ROM, internal modem
CD-ROM drive optional — an education configuration was sold without one.<ref name="ss-520" /><ref name="everymac-575" />
* '''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 ==


== General Maintenance ==
The LC 575 is an all-in-one: mains-powered analogue board, CRT and logic board in one case. Before doing
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]].
anything inside it, read [[CRT Discharge Procedure]]. The anode holds a charge after the machine is
switched off and unplugged, and the analogue board carries mains voltage on its primary side. Both are
live at the same time when the case is open.


== PCB Schematics & Service Manual ==
Routine care is the same as any beige Macintosh of the period: keep the vents clear, do not run it in a
sealed cabinet, check the PRAM battery every few years and take it out before storage, and clean the
front-panel contrast and volume buttons rather than forcing them. For yellowed plastics see
[[Retrobrite]]; for battery and electrolyte damage see
[[Battery Explosion, Capacitor or Corrosion Damage]].


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 and service parts ==


=== Logic Board ===
The logic board is '''820-0464-B''' (copyright 1993, 1994).<ref name="ram-575">[https://recapamac.com.au/macintosh-lc575/ Recap-a-Mac — Macintosh LC575]. Annotated photograph of the 820-0464-B logic board. Hosted on this wiki as [[:File:Mac LC 575 Recap Guide.jpg]]. Secondary source.</ref> Apple's service part numbers for
The logic board shares architecture with the [[Macintosh LC 475]] and [[Macintosh Quadra 605]], featuring:
this family are:
* '''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 ===
<templatestyles src="Template:StyledTable/styles.css" />
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.
{| class="wikitable styled-table" style="width:80%;"
|+ Apple service parts, LC 520 / 550 / 575<ref name="ss-520" />
! Part !! Number
|-
| Logic board, LC 575 || 661-0867
|-
| Logic board, LC 550 || 661-1830
|-
| Logic board, LC 520 || 661-0812
|-
| Analogue board (all three models) || 661-0192
|-
| CRT || 661-1666; 661-1667 (Australia); 661-1668 (Europe)
|-
| Floppy drive, manual insert || 661-0121
|-
| CD-ROM drive || 661-0222
|-
| Fan || 922-1803
|-
| Internal microphone || 922-1802
|}
 
There is '''one''' analogue board part number for the whole family. Apple specifies the supply as
universal, 100–240 VAC at 47–63 Hz, so unlike some machines of this era there is no
separate 115 V and 230 V board to confuse when ordering parts or reading capacitor
lists.<ref name="ss-520" /> The CRT, by contrast, does have regional part numbers.
 
The board photograph below shows an AM53C96 SCSI controller and a Zilog Z8530 serial communications
controller alongside four Apple ASICs marked 343S0129-C, 343S0138-A, 343S0164-b and
343S1091-A.<ref name="ram-575" /> Apple's Service Source for this machine is module-level and does not describe what
those ASICs do, so this wiki does not claim to either.
 
=== Apple service manual ===


=== Apple Service Manual ===
<pdf width="800" height="500">File:Lc 520.550.575.pdf</pdf>
<pdf width="800" height="500">File:Lc 520.550.575.pdf</pdf>


Service documentation available on the [[:Category:Apple Service Source|Apple Service Source]] page.
Download the Macintosh LC 520/550/575 Service Source here: [[:File:Lc 520.550.575.pdf]]. Further
documentation is listed under [[:Category:Apple Service Source]].
 
=== Schematic ===
 
<pdf>File:LC575.pdf</pdf>
 
Download the Macintosh LC 575 schematic here: [[:File:LC575.pdf]]
 
== Capacitor replacement ==
 
The LC 575 logic board carries '''twelve surface-mount electrolytic capacitors''':
 
* '''10 × 47 µF 16 V'''
* '''2 × 100 µF 6.3 V'''
 
These figures come from Recap-a-Mac's annotated photograph of an 820-0464-B board, which is also the
location map — there is no second published list for this board to cross-check against, and Apple
never published component-level capacitor data for any Macintosh of this era.<ref name="ram-575" /> Read the value
printed on each capacitor body before you lift it.
 
[[File:Mac LC 575 Recap Guide.jpg|center|thumb|700px|Macintosh LC 575 logic board 820-0464-B, with each
electrolytic marked with its value, working voltage and positive terminal. Source: Recap-a-Mac.]]


== Capacitor Replacement Guide ==
Leaking SMD electrolytics on this generation show up first as lost or distorted sound, then as
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.
intermittent starting, and finally as corroded copper under the solder mask. The removal and fitting
procedure is identical to the rest of the LC family and is documented on
[[Macintosh LC Capacitor Replacement Guide]]; see also [[Capacitor Failure Symptoms]].


== Retrobrite ==
The analogue board carries its own electrolytics, on a board that is mains-connected and shares a case
{{Main|Retrobrite}}
with a charged CRT. No published per-designator list for the 661-0192 analogue board was found while
The LC 575's beige plastics yellow from UV exposure and bromine flame retardants. Restoration techniques are detailed on the [[Retrobrite]] page.
this page was verified, so none is given here.


== Troubleshooting ==
== Display adjustments ==
Common issues including power supply failures, CRT problems, and capacitor-related failures are covered in the [[Macintosh LC 575 Troubleshooting]] guide.


== Technical Details ==
Apple's Adjustments chapter gives figures you can check with a ruler and the Display Service
<templatestyles src="Template:StyledTable/styles.css" />
Utility's test patterns.<ref name="ss-520" /> All of the adjustment controls are in the high-voltage area of the
analogue board; Apple specifies a short plastic hex-head tool and warns explicitly against metal
alignment tools.


=== System Architecture ===
{| class="wikitable styled-table" style="width:80%;"
{| class="wikitable styled-table" style="width:90%; text-align:center;"
|+ Apple geometry targets, LC 520/550/575<ref name="ss-520" />
! Sub-system !! Specification (Macintosh LC 575, February 1994)
! Adjustment !! Target
|-
|-
| '''CPU''' || Motorola 68LC040 @ 33 MHz (66 MHz clock, divided by 2)
| Raster height (VH) || 7 in ± 1/8 in (176 mm ± 2 mm) on an all-white screen
|-
|-
| '''Bus width''' || 32-bit data • 32-bit address (4 GB addressable space)
| Raster width (HW) || 9 1/4 in ± 1/8 in (235 mm ± 2 mm) on an all-white screen
|-
|-
| '''ROM''' || '''1 MB ROM''' – System 7.1 ROM with 68040 support
| Vertical / horizontal centre (VS, HS) || Raster centred in the display area
|-
|}
| '''RAM''' || 4 MB soldered (expandable to 36 MB via single 72-pin SIMM)
 
|-
Cutoff and white balance are set on the Gray Bars pattern after the monitor has been on for at least ten
| '''L1 Cache''' || 8 KB unified instruction/data cache (on-chip)
minutes, with contrast at maximum and the Screen control panel brightness at midrange. Cutoff is set
first, with VG2 adjusted until the first bar is completely black and the second is barely visible; white
balance follows on the red, green and blue background and drive controls. Apple requires the cutoff
adjustment whenever the CRT or the analogue board is replaced.<ref name="ss-520" />
 
== Technical details ==
 
=== System ===
 
{| class="wikitable styled-table" style="width:90%;"
! Sub-system !! Specification
|-
|-
| '''Video''' || 640 × 480 color (14" Sony Trinitron) • 512 KB VRAM standard (1 MB max)
| Processor || Motorola 68LC040, 33 MHz, built-in MMU, no FPU. Socket for an optional coprocessor<ref name="ss-520" />
|-
|-
| '''Color depth''' || 256 colors (8-bit) at 512 KB VRAM • 32,768 colors (16-bit) at 1 MB VRAM
| Processor upgrade || Socketed; Apple's Macintosh Processor Upgrade fits a PowerPC 601 with a 256 K cache card and re-seats the customer's 68LC040 on the upgrade board<ref name="ss-520" />
|-
|-
| '''Sound''' || Stereo 16-bit sound • 44.1 kHz sample rate • Built-in stereo speakers
| ROM || 1 MB<ref name="ss-520" />
|-
|-
| '''Storage''' || 1.44 MB SuperDrive • 160-320 MB SCSI hard drive • 2X CD-ROM (optional)
| RAM || 4 MB on board, expandable to 36 MB through a single 72-pin SIMM socket<ref name="ss-520" />
|-
|-
| '''I/O Ports''' || ADB × 1 • DB-25 SCSI • Mini-DIN-8 serial × 2 • Microphone • Headphone
| PRAM || 256 bytes of clock/calendar/parameter memory<ref name="ss-520" />
|-
|-
| '''Expansion''' || '''LC PDS''' + '''Comm Slot''' (first Mac with Communication Slot)
| VRAM || 512 K on board for 8-bit colour, expandable to 1 MB for 16-bit colour, across two VRAM SIMM slots<ref name="ss-520" />
|}
 
=== Memory Configuration ===
{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''Memory Expansion Options'''
! Configuration !! Soldered RAM !! SIMM Slot !! Total RAM
|-
|-
| Minimum || 4 MB || Empty || 4 MB
| Display || 14 in Trinitron with high-contrast glass, 13 in viewable, 0.26 mm aperture grille pitch, 640 x 480 at 70 dpi<ref name="ss-520" />
|-
|-
| Standard (LC 575) || 4 MB || 1 MB || 5 MB
| Sound || Stereo sound output port and front headphone jack; monaural sound input; records at 11 or 22 kHz, plays back at 22 kHz; two speakers; built-in electret omnidirectional microphone<ref name="ss-520" />
|-
|-
| Upgraded || 4 MB || 4 MB || 8 MB
| Storage || Manual-insert 1.4 MB SuperDrive; 3.5 in internal SCSI hard drive of 80, 160, 250 or 320 MB; internal Apple CD 300+ CD-ROM drive<ref name="ss-520" />
|-
|-
| Enhanced || 4 MB || 8 MB || 12 MB
| Expansion || One processor-direct slot taking 96-pin or 114-pin cards, plus a communications slot for 50-pin modem and Ethernet cards<ref name="ss-520" />
|-
|-
| High-end || 4 MB || 16 MB || 20 MB
| Gestalt ID || 92<ref name="everymac-575" />
|-
| Maximum || 4 MB || 32 MB || 36 MB
|}
|}


'''SIMM Requirements:'''
'''SIMM speed:''' Apple's LC 520/550/575 volume specifies "100 ns or faster" for the DRAM
* 72-pin, 80ns or faster
SIMM.<ref name="ss-520" /> Third-party references commonly quote 80 ns as the requirement.<ref name="everymac-575" /> Faster is
* Supports 1, 2, 4, 8, 16, 32 MB modules
always safe; the two figures do not agree and the discrepancy is noted here rather than resolved.
* Single-banked 64 MB SIMMs work but double-banked do not
 
* Installation requires partial disassembly of the computer
=== Memory configurations ===
 
The machine has 4 MB soldered and one SIMM socket, so the total is 4 MB plus whatever is in the
socket, to a maximum of 36 MB.<ref name="ss-520" /> Apple's standard configurations were 5 MB (a 1 MB
SIMM) and 8 MB (a 4 MB SIMM).<ref name="everymac-575" />
 
=== I/O ports ===


=== Built-in Display Specifications ===
{| class="wikitable styled-table" style="width:90%;"
{| class="wikitable styled-table" style="width:90%; text-align:center;"
|+ From Apple's I/O Interfaces specification<ref name="ss-520" />
! Parameter !! Specification
! Port !! Connector !! Notes
|-
| '''Display Type''' || Sony Trinitron aperture grille CRT
|-
| '''Screen Size''' || 14" diagonal (12.4" viewable)
|-
|-
| '''Resolution''' || 640 × 480 pixels native
| Serial x 2 || Mini-DIN-8 || RS-232 / RS-422
|-
|-
| '''Alternate Mode''' || 560 × 384 pixels (Apple IIe Card compatibility)
| SCSI || DB-25 || Up to six external devices
|-
|-
| '''Refresh Rate''' || 66.67 Hz
| Apple Desktop Bus || Mini-DIN-4 || Apple's specification for this family lists two ADB ports, a maximum of three ADB devices, and 500 mA maximum current draw (mouse 10 mA, keyboard 25 mA)
|-
|-
| '''Dot Pitch''' || 0.28mm aperture grille
| Sound output || 3.5 mm || Stereo; plus a stereo headphone jack on the front bezel
|-
|-
| '''VRAM''' || 512 KB standard (256 colors) • 1 MB maximum (32,768 colors)
| Sound input || 3.5 mm || Monaural
|}
|}


The Trinitron tube provides superior color reproduction and brightness compared to shadow mask CRTs, though characteristic horizontal stabilization wires are visible across the screen.
=== Communications slot ===
 
=== Communication Slot (Comm Slot) ===
 
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) ===
 
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 describes the communications slot simply as internal expansion for '''50-pin''' modem and Ethernet
* '''Apple IIe Card''' – Apple II emulation
cards, and lists it as one of the three features that distinguish the LC 575 from the LC 520 and LC
* '''PowerPC Upgrade Card''' – 50-100 MHz PowerPC 601
550.<ref name="ss-520" /> EveryMac records the LC 575 as the first LC-series model to carry one.<ref name="everymac-575" /> No
* '''Video capture cards''' – Various manufacturers
verified list of compatible cards and their Apple part numbers was found while this page was checked, so
* '''Accelerator cards''' – 68040 and PowerPC upgrades
none is given.


=== PowerPC Upgrade Path ===
=== Electrical, physical and environmental ===


Apple offered the '''Macintosh Processor Upgrade Card''' (November 1994 - March 1996) providing:
{| class="wikitable styled-table" style="width:80%;"
* '''PowerPC 601 processor''' at 50 MHz (Apple) or 100 MHz (third-party)
|+ Apple specification<ref name="ss-520" />
* Plugs into LC PDS slot
! Item !! Specification
* 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 ===
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! 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
| Line voltage || 100–240 VAC, universal power supply
|-
|-
| '''CUDA''' || ADB/Power management || Handles ADB, power control, PRAM
| Frequency || 47–63 Hz, single phase
|-
|-
| '''AWACS''' || Audio controller || 16-bit stereo sound generation
| Maximum power || 120 W
|}
 
=== I/O Ports & Connectivity ===
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Port !! Type !! Function !! Notes
|-
|-
| ADB || Mini-DIN-4 || Keyboard/Mouse || Single port (daisy-chain capable)
| Dimensions || 17.9 in (45.5 cm) H x 13.5 in (34.4 cm) W x 16.5 in (42.0 cm) D
|-
|-
| Serial (Modem) || Mini-DIN-8 || RS-422/RS-232 || Disabled when Comm Slot modem installed
| Weight || 40.5 lb (18.4 kg)
|-
|-
| Serial (Printer) || Mini-DIN-8 || RS-422/LocalTalk || AppleTalk networking capable
| Operating temperature || 50–104 °F (10–40 °C)
|-
|-
| SCSI || DB-25 || External SCSI || Requires termination for external devices
| Storage temperature || −40 to 149 °F (−40 to 65 °C)
|-
|-
| Audio In || 3.5mm jack || Microphone || PlainTalk compatible
| Relative humidity || 20–95 %, non-condensing
|-
|-
| Audio Out || 3.5mm jack || Headphones/Speakers || Stereo output
| Altitude || 0–10,000 ft operating
|}
|}


=== Power Specifications ===
== PRAM battery ==
* '''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 ===
* '''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 ==
 
=== Operating System Support ===
* '''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 ===
* System Enabler 065 (original)
* System Enabler 364 (updated)
* Not required with System 7.5 and later


== Historical Context ==
Apple's specification for the LC 520/550/575 lists a long-life lithium battery, and Apple's service
check is to measure it on the 10 V DC range and replace it if it reads below '''3.0 V'''. On
the LC 575 the battery is attached with hook-and-loop fastener rather than clipped into a holder, and
Apple's take-apart sequence removes the I/O door, the logic board and then the battery.<ref name="ss-520" />


The LC 575 represented several technical transitions for Apple:
'''There is a source conflict here.''' EveryMac lists the LC 575's battery as a 4.5 V alkaline
pack.<ref name="everymac-575" /> Apple's own manual for this machine says lithium and gives a 3.0 V replacement
threshold, which does not fit a 4.5 V pack. Open the machine and look at what is actually fitted
before ordering a replacement — and measure it while it is in there.


* '''Architecture migration''' – Shifted from 68030 (LC 520/550) to 68040 architecture
Whatever is fitted, a cell left in a stored machine is one of the two great destroyers of boards of this
* '''Performance positioning''' – Provided Quadra-level performance at LC pricing
age; the other is the capacitors. See
* '''Expansion innovation''' – Introduced Communication Slot standard used through 1997
[[Battery Explosion, Capacitor or Corrosion Damage]] and [[Battery Refurbishment]].
* '''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.
== Software ==


== Known Issues & Quirks ==
Apple shipped the LC 575 with System 7.1. EveryMac records the supported range as System 7.1 to 7.5.1
and 7.5.3 to Mac OS 8.1.<ref name="everymac-575" />


=== Logic Board Issues ===
== Known issues and quirks ==
* '''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 ===
* '''SMD capacitor leakage.''' Assume an un-recapped board needs it. See above.
* '''Trinitron stabilization wires''' – Two horizontal lines visible across screen (normal)
* '''PRAM battery corrosion.''' As above.
* '''Geometry drift''' – Magnetic fields affect display alignment over time
* '''Trinitron damper wires.''' Two faint horizontal lines are visible across the screen on any
* '''Analog board capacitors''' – Age-related failures cause display instability
  aperture-grille tube. They are part of the tube's construction, not a fault.
* '''Flyback transformer''' – High-voltage section prone to failure after extended use
* '''Heat.''' The logic board, the analogue board and a CRT share one sealed-ish case. Blocked vents are
  a real cause of intermittent faults on this chassis.
* '''The "Mystic" upgrade.''' The LC 575 logic board is widely transplanted into a
  [[Macintosh Color Classic]] case by enthusiasts. Apple did something similar itself: its own PowerPC
  upgrade for the LC 520 and LC 550 consists of an LC 575 logic board, the PowerPC Upgrade Card, a new
  rear panel and a 575 product ID label.<ref name="ss-520" /> This is the main reason bare LC 575 boards are scarce
  and complete machines are often found gutted.


=== Compatibility Considerations ===
== Related pages ==
* '''"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 ==
* [[Macintosh LC 520]]
* [[Macintosh LC 575 General Maintenance]] – Regular cleaning and care
* [[Macintosh LC 550]]
* [[Macintosh LC 575 Capacitor Replacement Guide]] – SMD capacitor specifications
* [[Macintosh LC 580]]
* [[Macintosh LC 575 Troubleshooting]] – Diagnostic procedures
* [[Macintosh LC 475]] and [[Macintosh Quadra 605]] — the same processor in the pizza-box chassis
* [[CRT Discharge Procedure]] – Safety for internal work
* [[Macintosh LC Capacitor Replacement Guide]] — shared recapping procedure
* [[Macintosh Communication Slot]] – Expansion card information
* [[Macintosh LC 520/550/575 Service Source]]
* [[CRT Discharge Procedure]]
* [[Retrobrite]]


== Related Pages ==
== References ==
* [[Macintosh LC 520]] – First LC 500 series model
<references />
* [[Macintosh LC 550]] – Direct predecessor
* [[Macintosh LC 580]] – Direct successor
* [[Macintosh Quadra 605]] – Logic board donor
* [[Macintosh Color Classic]] – Popular upgrade recipient


[[Category:Apple Vintage Computers]]
[[Category:Apple Vintage Computers]]
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