Apple 21" Color Display
| Macintosh 21" Color Display | |
|---|---|
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| Macintosh 21" Color Display (All About Apple museum, CC BY-SA 3.0) | |
| Manufacturer | Apple Computer, Inc. |
| Type | 21-inch colour CRT monitor |
| Release date | October 1991 |
| Discontinued | March 1994 |
| Interface | Analogue RGB (RS-343), DB-15 video cable; three ADB ports |
| Dimensions | 470 × 498 × 530 mm (H × W × D) |
| Weight | 36.2 kg (79.6 lb) |
| Model | M3502 |
| Power | 85-135 V and 170-270 V AC, 47-63 Hz, 165 W maximum |
| Resolution | 1152 × 870, 79 dpi |
The Macintosh 21" Color Display is Apple's large colour monitor of the early 1990s, sold from October 1991 to March 1994 with the model number M3502.[1] It shows 1152 × 870 at 75 Hz on a 21-inch dot-screen tube with a 20-inch viewable image, which is why some histories of Apple's displays list it as the 20-inch member of the Macintosh colour display range.[2][3] Inside, it carries a magnetometer and position sensor that let it degauss itself whenever the stand is tilted or turned, and six status LEDs that Apple's service procedure uses to find a fault.[2][4]
Specifications
[edit | edit source]| Item | Value |
|---|---|
| Picture tube | 21 in diagonal, 20 in viewable; 90° deflection; black-matrix dot screen, 0.26 × 0.29 mm dot pitch; P22 phosphor; flat, square grey filter glass (about 50% transmission), anti-static coating |
| Resolution | 1152 × 870, 79 dpi; up to 256 colours with the Macintosh Display Card 8•24 or 8•24 GC |
| Scan rates | Vertical 75 Hz; horizontal 68.7 kHz; rise and fall time 5 ns maximum |
| Active display area | 14.6 × 11.0 in (371 × 280 mm) |
| Controls | Brightness and contrast on the front; power and manual degauss switches on the back |
| Stand and ports | Built-in tilt-and-swivel stand; automatic degauss whenever it is tilted or swivelled; three ADB ports (two front, one rear) |
| Power supply | Universal, 85-135 and 170-270 V AC self-configuring, 47-63 Hz, 165 W maximum |
| Size and weight | 18.5 in (470 mm) high, 19.6 in (498 mm) wide, 20.9 in (530 mm) deep; 79.6 lb (36.2 kg) |
| Operating environment | 10-35 °C; 95% humidity maximum, non-condensing; up to 10,000 ft |
Apple's online specification page gives the viewable size as 19 in.[5]
Hardware
[edit | edit source]The display is built from a main board, a separate power supply board, a flyback transformer assembly with a high-voltage block, a video assembly with video filter boards, a magnetometer degauss board with its magnetometer and degauss coils, a position sensor board and an internal ADB cable to the stand.[6]
| Part | Apple number |
|---|---|
| CRT assembly | 076-0394 |
| Main board assembly | 661-0656 |
| Power supply board | 661-0658 |
| Video assembly | 661-0655 |
| Flyback transformer assembly | 661-1132 |
| Magnetometer degauss board | 661-0657 |
| Position sensor board | 982-0096 |
| Magnetometer coils / degauss coils | 076-0403 / 076-0405 |
| Video filter board | 076-0404 |
| On/off switch filter assembly (carries the fuse) | 076-0398 |
The CRT and main board came in matched Rev. A and Rev. B versions. A Rev. B CRT has a small blue label reading "NEW" near the anode; a Rev. B main board has capacitor C153 on one side or the other, and removing C153 converts a Rev. B board to Rev. A.[7] Apple supported CRT replacement only on international units; on domestic units a suspected tube failure was referred to Apple Technical Support.[8]
Known faults and normal behaviour
[edit | edit source]- A dark screen is diagnosed from the six LEDs: V125 and V810 on the main board, V683, V684, V685 and V699 on the power supply board. All should be lit. The flowchart is on the troubleshooting guide.[4]
- Large monitors distort near metal furniture and jitter near fluorescent lights; Apple says to rule out the location before adjusting or replacing anything, and to face the display magnetic north or south when adjusting it.[9]
- Jitter or a wavy picture at 1152 × 870 on a Power Macintosh 9600 is caused by early Apple/IMS video cards (serial numbers below Fx705xxx), not the display.[8]
No component-level repair reports or capacitor list for this display have been found, and Apple's service documents give no component values.
Maintenance and repair
[edit | edit source]- Apple 21" Color Display General Maintenance: magnetic alignment, geometry with the diagnostic overlay, horizontal hold (4.1 V at TP254), convergence, focus and video (27 foot-lamberts).
- Apple 21" Color Display Troubleshooting Guide: the LED flowchart and Apple's symptom charts.
The CRT keeps a charge after switch-off; follow the CRT Discharge Procedure before working inside.
Documentation
[edit | edit source]- Macintosh 21 Color Display Service Source: Apple's 191-page Service Source.
- Apple Macintosh Displays and Video Cards Service Guide (1996), chapter 16: board drawings, parts list and adjustment fold-outs.[1]
Gallery
[edit | edit source]-
LEDs V125 and V810 on the main board (Apple Service Source) -
Exploded view with part numbers (Apple Service Source)
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Related pages
[edit | edit source]References
[edit | edit source]- ↑ 1.0 1.1 Apple Computer, Macintosh Displays and Video Cards service guide, September 1996, hosted as File:Apple Macintosh Displays and Video Cards Service Guide (September 1996).pdf. Table 1, model numbers, p. 12 (PDF p. 30); Table 2, dates, p. 13 (PDF p. 31); chapter 16, Macintosh 21" Color Display, pp. 227-265 (PDF pp. 245-283).
- ↑ 2.0 2.1 2.2 Apple Computer, Macintosh 21-inch Color Display (Service Source), hosted as File:21 color display.pdf. Specifications, pp. 1-6 (PDF pp. 13-18).
- ↑ Apple displays, Wikipedia—link(accessed 2026-10-02) History only: describes the 14-, 16- and "20-inch" Macintosh colour displays of 1992, the last at 1152 × 870.
- ↑ 4.0 4.1 Macintosh 21-inch Color Display Service Source, Basics, Troubleshooting LEDs, pp. 7-9 (PDF pp. 9-11).
- ↑ Macintosh 21-inch Color Display: Technical Specifications, Apple—link(accessed 2026-10-02)
- ↑ 6.0 6.1 Macintosh 21-inch Color Display Service Source, Exploded View (PDF p. 191); Take Apart, pp. 1-69 (PDF pp. 42-110).
- ↑ Macintosh 21-inch Color Display Service Source, Additional Procedures, Rev A/B Compatibility, pp. 1-4 (PDF pp. 112-115).
- ↑ 8.0 8.1 Macintosh 21-inch Color Display Service Source, Troubleshooting, Symptom Charts, pp. 2-18 (PDF pp. 21-37), and Troubleshooting LEDs, pp. 19-21 (PDF pp. 38-40).
- ↑ Macintosh 21-inch Color Display Service Source, Basics, Monitor Distortion, pp. 1-6 (PDF pp. 3-8); Adjustments, Aligning to Magnetic N/S, pp. 1-2 (PDF pp. 117-118).