Macintosh LC 520
 | |
| Macintosh LC 520 | |
| Specifications | |
|---|---|
| Manufacturer | Apple Computer, Inc. |
| Type | All-in-one personal computer |
| Released | 28 June 1993 |
| Discontinued | 2 February 1994 |
| Intro price | US$1,599 (education) |
| CPU | Motorola 68030 at 25 MHz |
| Memory | 4 MB on the logic board; one 72-pin SIMM socket; 36 MB maximum |
| Storage | Internal 80, 160, 250 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 | 512 KB VRAM on the board plus one 68-pin socket for a 256 KB SIMM (768 KB maximum) |
| ROM | 1 MB, socketed |
| FPU / coprocessor | Socket for an optional 68882 |
| Media | 1.4 MB Apple SuperDrive (auto-inject); AppleCD 300i CD-ROM drive (caddy) |
| Ports / interface | Two ADB, two serial (mini DIN-8), SCSI (DB-25), sound in and out |
| Expansion | One 114-pin processor-direct slot (takes 96-pin cards) |
| 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 7.6.1 |
| Predecessor | Macintosh LC III |
| Successor | Macintosh LC 550, Macintosh LC 575 |
| Codename | Mongo |
| Model no. | M1640 |
The Macintosh LC 520 is an all-in-one Macintosh with a built-in 14-inch Trinitron display, made by Apple Computer from June 1993 to February 1994. Apple describes it as a larger version of the Macintosh Color Classic with many of the performance features of the Macintosh LC III: a 25 MHz 68030 with a 32-bit data bus, 4 MB of RAM expandable to 36 MB, stereo speakers and room for an internal CD-ROM drive.[1] Apple's service manual covers it with the Macintosh LC 550 and Macintosh LC 575, which use the same case.[2]
History
[edit | edit source]The LC 520 was introduced on 28 June 1993, under the design codename Mongo.[3][4] Apple adapted the Color Classic's design for a larger display and a CD-ROM drive; according to Paul Kunkel's history of Apple's industrial design group, the designers disliked the result and began the redesign that became the Power Macintosh 5200 LC.[3] In the United States it was sold only to schools, at US$1,599; it was also sold in Canada and Japan.[3] It was replaced in February 1994 by the 33 MHz LC 550 and the 68LC040-based LC 575.[3][4]
Specifications
[edit | edit source]| Item | Specification |
|---|---|
| Processor | Motorola 68030 at 25 MHz, built-in MMU; socket for an optional math coprocessor |
| RAM | 4 MB on the board, expandable to 36 MB with one 72-pin SIMM |
| ROM | 1 MB |
| PRAM | 256 bytes; long-life lithium battery |
| VRAM | 512K on the board; 68-pin VRAM SIMM socket |
| Floppy drive | Internal 1.4 MB Apple SuperDrive, auto-inject |
| Hard disk | 3.5-inch internal 80, 160, 250 or 320 MB SCSI |
| CD-ROM | Internal AppleCD 300i |
| I/O | Two RS-232/RS-422 serial (mini DIN-8); SCSI (DB-25), up to six external devices; two ADB (mini DIN-4), three devices recommended, 500 mA maximum |
| Expansion | Processor-direct slot for 96- or 114-pin cards |
| Sound | Records at 11 or 22 kHz, plays at 22 kHz; two speakers; stereo output port and front headphone jack; mono input port |
| 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 |
The table is from the Service Source.[2] The Service Source asks for SIMMs of 100 ns or faster; the Developer Note asks for 80 ns or faster.[2][1]
Hardware
[edit | edit source]Logic board and memory
[edit | edit source]The logic board slides out of the back of the case: push down the two tabs above the ports, lift off the connector cover (the I/O door), and pull the board out of its socket at the front.[1] Apple's Service Source reminds technicians that this ease of access does not remove the need for ESD precautions.[2] The logic board is Apple part 661-0812.[2]
The board has 4 MB of RAM and takes one 72-pin SIMM of 1, 2, 4, 8, 16 or 32 MB, for 5 to 36 MB.[1] The 1 MB ROM is socketed, with provision for expansion to 2 MB.[1] Custom chips: Ardbeg (timing, memory mapping, the VIAs, video timing, the SWIM II floppy controller, sound control and the front-panel buttons), Ariel (video CLUT and DAC), Combo (serial and SCSI controller in one), Cuda (ADB, parameter RAM, clock and soft power) and DFAC II (sound conversion).[1]
Video
[edit | edit source]The LC 520 has 512 KB of VRAM on the board and one 68-pin socket for a 256 KB VRAM SIMM of 80 ns or faster. With 512 KB the display shows up to 8 bits per pixel; with the SIMM, 768 KB gives 16 bits per pixel (32,768 colours).[1] There is no external video connector.[1] The Service Source's shared VRAM entry for the three models ("expandable to 1 MB") applies to the LC 575, which has two VRAM SIMM slots.[2]
Sound
[edit | edit source]Two internal speakers give stereo output, with sound-output jacks at the front and back. The built-in microphone is at the front of the case. The rear input jack takes a mono or stereo plug, mixes stereo to mono, and supplies 5 V to Apple's external microphone through an extra contact.[1] The front-panel buttons adjust volume and screen brightness.[1]
Expansion
[edit | edit source]The processor-direct slot takes 114-pin LC III cards and 96-pin cards such as those for the Color Classic and LC II, including the Apple IIe Card, which gives a 560 × 384, 16-colour mode on the built-in display.[1] A card may draw 1.0 A at +5 V, 20 mA at −5 V and 200 mA at +12 V, and no more than 5 W in total.[1] The AppleCD 300i drive is budgeted 500 mA at +5 V and 800 mA at +12 V (1.5 A peak).[1]
SCSI termination
[edit | edit source]The internal end of the SCSI bus is terminated in the internal hard disk. At the external end, the logic board has a terminator near the external connector that is switched in when no external device is attached; when external devices are connected, the board detects their termination during system reset and switches its own terminator out.[1] The last external device therefore still needs its terminator, and a device added while the machine is running is not detected until the next restart. Apple lists the IIvx and Centris 650 as using the same arrangement.[1]
Power, analog board and CRT
[edit | edit source]The power supply is on the analog board, Apple part 661-0192, which also drives the CRT. The CRT is 661-1666 (661-1667 in Australia, 661-1668 in Europe); the fan is 922-1803.[2] Apple's Adjustments chapter covers geometry, focus, cutoff, white balance, convergence, geometric distortion, the yoke and light-meter setup, and gives no power-supply voltages or adjustment.[2]
Some analog boards have a test jumper at BD11. Apple's instruction is to remove it, because it makes the machine restart after shutdown.[2]
Battery
[edit | edit source]The clock and parameter RAM run from a lithium battery on the logic board. With the I/O door and logic board out, set a meter to the 10 V DC range and replace the battery if it reads below 3.0 V.[2] The holder cover is released by pushing a small flat-blade screwdriver down and out at each end.[2] "Perform battery verification" is Apple's fifth cure for a screen that is black, too dark or too bright.[2] Neutralise any leakage with bicarbonate of soda; see Battery Explosion, Capacitor or Corrosion Damage.
Safety
[edit | edit source]The analog board and CRT carry high voltage, and the CRT holds its charge after the machine is unplugged. Apple's procedures discharge the CRT and remove the anode cap before the analog board is touched, and warn never to wear a grounding wrist strap until the CRT has been discharged.[2] See CRT Discharge Procedure.
Take-apart
[edit | edit source]- Remove the five Torx screws from the rear housing and lift it off. If the rear cover shield has bronze tape on it, remove the tape and bend the centre ground pin back about 1/8 inch; Apple says not to refit the tape.[2]
- The fan comes out by pushing out its two latches.[2]
- For the analog board: discharge the CRT and remove the anode cap; disconnect the two ground cables from the degauss panels, the internal microphone connector, the degauss cable from BP2 and the CRT cable from BD1; then pull the CRT board straight off the neck of the tube. Apple warns that twisting or bending it can break the neck.[2]
- After replacing the analog board or the CRT, do the cutoff adjustment.[2]
Adjustments
[edit | edit source]Apple's adjustments use the Display Service Utility's test patterns and a short hex-head plastic tool; a long tool flexes, and metal tools are a shock hazard. Let the display warm up for at least 10 minutes before cutoff and white balance, and do cutoff first.[2]
| Adjustment | Control | Target |
|---|---|---|
| Vertical centre | VS | Raster centred top to bottom on the all-white pattern |
| Horizontal centre | HS | Raster centred side to side |
| Vertical size | VH | 7 in ± 1/8 in (176 mm ± 2 mm) |
| Horizontal size | HW | 9 1/4 in ± 1/8 in (235 mm ± 2 mm) |
Apple notes that the raster width can vary by up to 3/16 inch at each side depending on the Macintosh video timing in use.[2]
Capacitors
[edit | edit source]MacDat lists nine surface-mount electrolytics on the LC 520 logic board: two 100 µF 6.3 V, six 47 µF 16 V and one 10 µF 50 V. It has no reference photograph for this board.[5] MacDat gives the LC 550 board the same list with a 10 µF 16 V part.[6] Read the value on each capacitor before replacing it. Apple's Service Source gives no component values for the analog board, which Apple serviced by replacement, and neither Console5 nor Recap-a-Mac covers the LC 520. See Capacitor Failure Symptoms.
Troubleshooting
[edit | edit source]Selected entries from Apple's symptom charts for the LC 520, 550 and 575:[2]
| Symptom | Apple's cures, in order |
|---|---|
| No video, no sound, no drive activity | Connect the power cord; switch on; power cord; keyboard; analog board; logic board |
| Screen black, too dark or too bright; sound and drives working | Contrast button; brightness in the Screen control panel; yoke cable; video adjustments; battery verification; analog board; CRT |
| Thin grey horizontal line across the lower third of a lit screen | Not a fault: it is part of the Trinitron design. Do not replace modules |
| Flashing or wavy screen, or a high-pitched noise | Analog board |
| Clicking, chirping or thumping | Analog board; logic board |
| Sad Mac with black vertical lines and a screeching sound | RAM SIMM; logic board |
| Restarts by itself after shutdown | Remove the test jumper at BD11 on the analog board, if fitted |
| Disk will not eject | Paper clip in the hole beside the drive; hold the mouse button down at power-on; remove the front drive bezel; floppy drive |
| Internal or external hard disk does not work | Check no SCSI loopback card is attached; external termination; hard disk; logic board; chassis harness |
| Works with internal or external SCSI device, not both | External device ID above 0 and not duplicated; external terminator; SCSI cable |
The start-up tones and Sad Mac codes are on Sad Mac Error Codes.
Documentation
[edit | edit source]- Macintosh LC 520/550/575 Service Source: Apple's service manual for the three models.[2]
- Macintosh LC 520 Developer Note: Apple's 1993 hardware description.[1]
Related pages
[edit | edit source]- Macintosh LC 550
- Macintosh LC 575
- Macintosh LC 580
- Macintosh TV
- Macintosh LC III
- CRT Discharge Procedure
- Macintosh Floppy Drive Maintenance
- Macintosh HDD Maintenance
References
[edit | edit source]- ↑ 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 1.15 Apple Computer, Macintosh LC 520 Computer Developer Note (1993), File:Macintosh LC 520 Developer Note.pdf; see Macintosh LC 520 Developer Note. Printed pages: pp. 1-3 (summary; comparisons with the Color Classic and LC III); p. 4 (logic board access from the rear); p. 6 (VRAM, soft power); p. 8 (RAM); pp. 10-12 (PDS, SCSI termination); pp. 13-16 (serial, ADB, sound, keyboard reset); pp. 20-22 (custom ICs); p. 36 (power for the expansion card); p. 50 (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 2.19 2.20 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; Fan pp. 41-42; Analog Board pp. 43-48; Logic Board pp. 51-52; Battery Verification and Replacement, LC 520, pp. 124-125 and 128-130; Adjustments pp. 134-174; Exploded View p. 176.
- ↑ 3.0 3.1 3.2 3.3 Macintosh LC 500 series, Wikipedia—link(accessed 2026-09-30) Codename Mongo and design history (Paul Kunkel, AppleDesign, Graphis, 1997, p. 243); US$1,599 education price and sale only to US schools, Canada and Japan (Peter H. Lewis, "Apple Offers Teachers An Extra-Value Deal", The New York Times, 17 August 1993); replaced by the LC 550 and LC 575 in February 1994, with upgrade kits.
- ↑ 4.0 4.1 Apple Macintosh LC 520 Specs, EveryMac—link(accessed 2026-09-30) Introduced 28 June 1993, discontinued 2 February 1994; model M1640, Gestalt ID 56; 4 MB on board, one 72-pin SIMM slot, 80 ns, 36 MB maximum; 512K VRAM soldered, one slot for a 256K VRAM SIMM, 768K maximum; System 7.1 to 7.6.1.
- ↑ Macintosh LC 520 Capacitor Reference, MacDat—link(accessed 2026-09-30) Logic board: 2 × 100 µF 6.3 V, 6 × 47 µF 16 V, 1 × 10 µF 50 V, surface-mount; no reference image. A secondary source.
- ↑ Macintosh LC 550 Capacitor Reference, MacDat—link(accessed 2026-09-30) Logic board: 2 × 100 µF 6.3 V, 6 × 47 µF 16 V, 1 × 10 µF 16 V.