Macintosh LC 575: Difference between revisions
Rewrite from Apple's Service Source, LC 575 Developer Note and the hosted Optimus schematic/BOM: designator capacitor table, battery part numbers, comm slot, VRAM; link the orphaned Developer Note; remove invented battery interval and uncited heat/damper-wire claims |
Battery: Apple's own spec page (112222) says 4.5 V alkaline, against the Optimus BOM's lithium parts; state both and give both clean-ups |
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=== Battery === | === Battery === | ||
The LC 575's battery is on a connector and a hook-and-loop base on the logic board, not in a clip-in holder. To replace it, remove the I/O door and logic board, pull up and disconnect the connector, and pull the battery off its base. Apple's test is the same as for the LC 520: 10 V DC range, replace below 3.0 V.<ref name="ss" /> The BOM in Apple's Optimus schematic set lists the battery (BT1) as 742-0025, with 742-0011, a 3.6 V battery, as the alternative.<ref name="sch" /> | The LC 575's battery is on a connector and a hook-and-loop base on the logic board, not in a clip-in holder. To replace it, remove the I/O door and logic board, pull up and disconnect the connector, and pull the battery off its base. Apple's test is the same as for the LC 520: 10 V DC range, replace below 3.0 V.<ref name="ss" /> The BOM in Apple's Optimus schematic set lists the battery (BT1) as 742-0025, with 742-0011, a 3.6 V battery, as the alternative.<ref name="sch" /> Apple's technical specifications page for the LC 575 gives the battery type as 4.5 V alkaline, as does EveryMac.<ref name="apple575">Apple, [https://support.apple.com/en-us/112222 "Macintosh LC 575: Technical Specifications"] (Battery Type: 4.5V alkaline). Retrieved 2026-10-01.</ref><ref name="everymac" /> Check the cell fitted before cleaning up a leak: lithium residue is neutralised with bicarbonate of soda, alkaline residue with a weak acid such as vinegar. See [[Battery Explosion, Capacitor or Corrosion Damage]]. | ||
=== Capacitors === | === Capacitors === | ||
Revision as of 17:35, 1 October 2026
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| Macintosh LC 575 | |
| Specifications | |
|---|---|
| Manufacturer | Apple Computer, Inc. |
| Type | All-in-one personal computer |
| Released | 2 February 1994 |
| Discontinued | 3 April 1995 |
| Intro price | US$1,700 |
| CPU | Motorola 68LC040 at 33 MHz (socketed; no FPU) |
| Memory | 4 MB on the logic board; one 72-pin SIMM socket; 36 MB maximum |
| Storage | Internal 160 or 320 MB SCSI hard disk |
| Display | Built-in 14-inch Trinitron, 640 × 480 |
| Sound | Stereo output, two speakers, front headphone jack; mono recording at 11 or 22 kHz; built-in microphone |
| Graphics | Two VRAM SIMM sockets, 512 KB or 1 MB |
| ROM | 1 MB, soldered |
| Media | 1.4 MB Apple SuperDrive (manual-inject); AppleCD 300+ CD-ROM drive (tray) |
| Ports / interface | ADB, two serial (mini DIN-8), SCSI (DB-25), sound in and out |
| Expansion | One LC-series expansion slot (96- or 114-pin cards); communications slot for a modem or Ethernet card |
| Power | 100-240 V AC, 47-63 Hz, 120 W maximum |
| Dimensions | 17.9 × 13.5 × 16.5 in (45.5 × 34.4 × 42.0 cm) |
| Weight | 40.5 lb (18.4 kg) |
| OS / Firmware | System 7.1 to Mac OS 8.1 |
| Predecessor | Macintosh LC 520 |
| Successor | Macintosh LC 580 |
| Codename | Optimus |
| Model no. | M1640 |
The Macintosh LC 575 is an all-in-one Macintosh made by Apple Computer from February 1994 to April 1995. Apple describes it as the case and 14-inch Trinitron display of the Macintosh LC 520 with the electrical design of the Macintosh LC 475: a 33 MHz 68LC040, the same custom chips and expansion slot, and a new communications slot for a modem or Ethernet card.[1] Apple's service manual covers it with the LC 520 and Macintosh LC 550.[2]
History
The LC 575 was introduced on 2 February 1994, alongside the LC 550, and discontinued on 3 April 1995; its codename was Optimus.[3][4] Apple's schematic for the logic board is titled "Optimus".[5] It was also sold as the Performa 575, 577 and 578.[4] The LC 575 is sometimes listed at 66 MHz; Apple gives 33 MHz, and EveryMac explains the higher figure as the clock input to a processor that is not clock-doubled.[2][3]
Apple's PowerPC upgrade for the LC 520 and LC 550 consisted of an LC 575 logic board, the PowerPC upgrade card, a new rear panel and an LC 575 product label.[2] Recap-a-Mac notes that LC 575 logic boards are often removed and fitted into Color Classic cases (the "Mystic" upgrade).[6]
Specifications
| Item | Specification |
|---|---|
| Processor | Motorola 68LC040 at 33 MHz (no FPU), in a socket |
| RAM | 4 MB on the board, expandable to 36 MB with one 72-pin SIMM |
| ROM | 1 MB, soldered |
| VRAM | Two 68-pin VRAM SIMM sockets, 512 KB or 1 MB; no VRAM on the board |
| Floppy drive | Internal 1.4 MB Apple SuperDrive, manual-inject |
| Hard disk | 160 or 320 MB SCSI (Developer Note); 80, 160, 250 or 320 MB (Service Source) |
| CD-ROM | AppleCD 300+ (tray-loading) |
| Expansion | One slot for 96-pin LC II or 114-pin LC III/LC 520 cards; communications slot for a modem or Ethernet card |
| Sound | Records at 11 or 22 kHz, plays at 22 kHz; two speakers; stereo output jack and front headphone jack; mono input |
| Display | 14-inch diagonal, 13-inch viewable Trinitron; 0.26 mm aperture grille pitch; 640 × 480 at 70 dpi |
| Power | 100-240 V AC universal supply; 47-63 Hz; 120 W maximum |
| Size and weight | 17.9 × 13.5 × 16.5 in (45.5 × 34.4 × 42.0 cm); 40.5 lb (18.4 kg) |
| Environment | Operating 10-40 °C; storage −40 to 65 °C; 20-95 % relative humidity; up to 10,000 ft |
From the Developer Note and the Service Source.[1][2] The Service Source asks for SIMMs of 100 ns or faster; the Developer Note asks for 80 ns or faster.[2][1] The Service Source lists two ADB ports for the three models; the Developer Note's comparison table gives the LC 575 one.[2][1]
Hardware
Logic board
The logic board is Apple part 661-0867 and is printed "820-0464-B".[2][6] It slides out of the back after the connector cover is released with the two tabs above the ports.[1] The custom chips are those of the LC 475: MEMCjr (memory and video controller), PrimeTime (I/O bus, SWIM II floppy controller, VIAs and sound buffers), DFAC II (sound conversion), Cuda (ADB, parameter RAM, clock and soft power) and Antelope (video CLUT and DAC).[1]
The 68LC040 is in a socket. Apple's Macintosh Processor Upgrade fits a PowerPC 601 card with a 256K cache card into that socket and carries the original 68LC040 in a socket of its own, so the machine can run on either processor.[2]
Memory and video
The board has 4 MB of RAM and one 72-pin SIMM socket for 1 to 32 MB SIMMs, giving 5 to 36 MB.[1] All video memory is on two 68-pin VRAM SIMMs; both sockets must be filled, with SIMMs of the same size (256 KB or 512 KB each), for 512 KB or 1 MB.[1] With 1 MB the built-in display runs at 16 bits per pixel.[2] There is no external video connector.[1]
Communications slot
The LC 575 has a socket on the logic board for one of three communications cards: a modem, Ethernet with an AUI connector, or Ethernet with a 10BASE-T connector. Apple states that the socket is not a general expansion connector.[1] The Service Source describes it as internal expansion for 50-pin modem and Ethernet cards.[2]
Expansion slot
The expansion slot is the LC 475's: it takes 96-pin LC II cards and 114-pin LC III and LC 520 cards, but it is not connected directly to the 68LC040.[1] A card may draw 800 mA at +5 V, 20 mA at −5 V and 200 mA at +12 V, 4 W in all.[1] The CD-ROM drive is budgeted 500 mA at +5 V and 800 mA at +12 V (1.5 A peak).[1]
SCSI
The internal hard disk terminates the internal end of the SCSI bus.[1] Apple's chart for a machine that works with the internal or an external device but not both checks that the external device's ID is above 0 and not duplicated, then the external terminator, then the SCSI cable.[2]
Analog board, CRT and power
The power supply is on the analog board, Apple part 661-0192, shared with the LC 520 and LC 550, which also drives the CRT (661-1666; 661-1667 Australia, 661-1668 Europe).[2] The supply is universal, 100-240 V AC, with no voltage selector.[2] Apple gives no power-supply voltages or adjustment; its Adjustments chapter covers the display only. Remove the test jumper at BD11 on the analog board, if fitted: it makes the machine restart after shutdown.[2]
The analog board and CRT carry high voltage, and the CRT holds its charge after the machine is unplugged. Apple discharges the CRT and removes the anode cap before touching the analog board, and warns never to wear a grounding wrist strap until the CRT is discharged.[2] See CRT Discharge Procedure. The take-apart sequence and Apple's geometry targets are on Macintosh LC 520; cutoff and white balance are set after at least 10 minutes' warm-up, cutoff first, and cutoff is repeated whenever the CRT or analog board is replaced.[2]
Battery
The LC 575's battery is on a connector and a hook-and-loop base on the logic board, not in a clip-in holder. To replace it, remove the I/O door and logic board, pull up and disconnect the connector, and pull the battery off its base. Apple's test is the same as for the LC 520: 10 V DC range, replace below 3.0 V.[2] The BOM in Apple's Optimus schematic set lists the battery (BT1) as 742-0025, with 742-0011, a 3.6 V battery, as the alternative.[5] Apple's technical specifications page for the LC 575 gives the battery type as 4.5 V alkaline, as does EveryMac.[7][3] Check the cell fitted before cleaning up a leak: lithium residue is neutralised with bicarbonate of soda, alkaline residue with a weak acid such as vinegar. See Battery Explosion, Capacitor or Corrosion Damage.
Capacitors
Apple's Optimus bill of materials (v4.1, 33 MHz) lists twelve surface-mount aluminium electrolytics and eight surface-mount tantalums on the logic board:[5]
| Designators | Value | Voltage | Type |
|---|---|---|---|
| C1, C4 | 100 µF | 6.3 V | Aluminium electrolytic, SMD |
| C2, C5, C8, C11, C12, C13, C15, C16, C17, C29 | 47 µF | 16 V | Aluminium electrolytic, SMD |
| C3, C7, C25, C26 | 10 µF | 16 V | Tantalum, SMD |
| C6, C9, C10, C14 | 3.3 µF | 16 V | Tantalum, SMD |
The BOM is from the engineering-validation stage, but its electrolytic count matches the production board: Recap-a-Mac's photograph of 820-0464-B and MacDat's list both give ten 47 µF 16 V and two 100 µF 6.3 V.[6][8] Apple gives no component values for the analog board. See Macintosh LC Capacitor Replacement Guide for the procedure and Capacitor Failure Symptoms.
Troubleshooting
Apple's symptom charts are shared with the LC 520 and LC 550; a selection is on Macintosh LC 520#Troubleshooting. A thin grey horizontal line across the lower third of a lit screen is part of the Trinitron design and not a fault, and a machine that restarts after shutdown has the BD11 test jumper fitted.[2] The start-up tones and Sad Mac codes are on Sad Mac Error Codes.
Documentation
- Macintosh LC 520/550/575 Service Source: Apple's service manual for the three models.[2]
- Macintosh LC 575 Developer Note: Apple's 1994 hardware description.[1]
- File:LC575.pdf: Apple's Optimus logic board schematic and bills of materials.[5]
Related pages
- Macintosh LC 520
- Macintosh LC 550
- Macintosh LC 580
- Macintosh LC 475
- Macintosh Color Classic
- Macintosh Processor Upgrade Service Source
- CRT Discharge Procedure
- Macintosh LC Capacitor Replacement Guide
References
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 Apple Computer, Macintosh LC 575 Computer Developer Note (1994), File:Macintosh LC 575 Developer Note.pdf; see Macintosh LC 575 Developer Note. Printed pages: pp. 2-3 (features; Table 1-1, comparison with the LC 520 and LC 475); p. 4 (logic board access); p. 6 (power switch); pp. 7-8 (RAM); p. 12 (VRAM); p. 14 (SCSI termination); p. 17 (communications options; ADB); p. 21 (expansion slot); pp. 24-28 (processor and custom ICs); p. 34 (gestaltMachineType 92); p. 52 (power for the expansion card); p. 60 (power for the CD-ROM drive).
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 Apple Computer, Macintosh LC 520, LC 550, LC 575 Service Source (1995), File:Lc 520.550.575.pdf; see Macintosh LC 520/550/575 Service Source. PDF page numbers: Product Information pp. 4-5; Specifications pp. 7-17; Symptom Charts pp. 20-36; Rear Housing pp. 38-40; Analog Board pp. 43-48; Logic Board pp. 51-52; Macintosh Processor Upgrade pp. 99-122 (LC 520 and 550 PowerPC upgrade p. 101); Battery Verification and Replacement, LC 575, pp. 126-127 and 131-132; Adjustments pp. 134-174; Exploded View p. 176.
- ↑ 3.0 3.1 3.2 Apple Macintosh LC 575 Specs, EveryMac—link(accessed 2026-09-30) Introduced 2 February 1994, discontinued 3 April 1995; US$1,700; model M1640, Gestalt ID 92; 33 MHz 68LC040 (the 66 MHz sometimes quoted is the clock input; the processor is not clock-doubled); socketed, upgradable to a 68040 or PowerPC 601; 5 MB or 8 MB standard; System 7.1 to Mac OS 8.1.
- ↑ 4.0 4.1 Macintosh LC 500 series, Wikipedia—link(accessed 2026-09-30) Codename Optimus; Performa 575, 577 and 578 variants; succeeded by the LC 580 and the Power Macintosh 5200 LC.
- ↑ 5.0 5.1 5.2 5.3 Apple Computer, "Optimus EVT1 Logic Board Schematic" (OPTIMUS_V41, 15 sheets, 1993) with the Optimus Main Logic Board BOMs v4.1-25MHz, v4.1-33MHz and v4.1 (EVT3), File:LC575.pdf. PDF pp. 1-15 schematic, pp. 16-24 BOMs. The 33 MHz BOM (PDF p. 19) gives C1, C4 100 µF 6.3 V and C2, C5, C8, C11, C12, C13, C15, C16, C17, C29 47 µF 16 V (126S1020, 126S4710, CAP_ELECSM_6MM); C3, C7, C25, C26 10 µF 16 V and C6, C9, C10, C14 3.3 µF 16 V tantalum; the EVT3 BOM (PDF p. 24) gives BT1 742-0025, alternative 742-0011 3.6 V. A pre-production (engineering validation) document; check against the board.
- ↑ 6.0 6.1 6.2 Macintosh LC575, Recap-a-Mac—link(accessed 2026-09-30) Annotated photograph of logic board 820-0464-B, hosted here as File:Mac LC 575 Recap Guide.jpg: 10 × 47 µF 16 V and 2 × 100 µF 6.3 V; LC 575 boards are commonly transplanted into Color Classics (the "Mystic" upgrade).
- ↑ Apple, "Macintosh LC 575: Technical Specifications" (Battery Type: 4.5V alkaline). Retrieved 2026-10-01.
- ↑ Macintosh LC 575 Capacitor Reference, MacDat—link(accessed 2026-09-30) Logic board: 2 × 100 µF 6.3 V, 10 × 47 µF 16 V, surface-mount; reference photograph.