Apple Macintosh Color Display Troubleshooting Guide

Macintosh Color Display (Ben Boldt, Wikimedia Commons, public domain)

Fault-finding on the Macintosh Color Display (M1212) from Apple's Service Source symptom charts. Try the cures in order; if replacing a module does not cure the fault, refit the original before trying the next cure.

Read CRT Discharge Procedure before opening the display, and Apple Macintosh Color Display General Maintenance for the adjustments the charts refer to.

Symptom charts

Macintosh Color Display symptom charts (Service Source pp. 2-11)

Symptom	Cures, in order
No raster, LED off	Check the power cable and power switch; check all connections on the main board; replace a blown fuse; replace the main board
No raster, LED on, CRT filament on	Adjust contrast and brightness; check the computer's video with a known-good monitor; check main board connections, with the video connector secure and its wires inside the plastic connector; do the video adjustments; replace the main board; the CRT
Raster too short, tall, narrow or wide	Adjust vertical or horizontal size; replace the main board
Raster not centred	Move the display away from monitors, fluorescent lights and other electrical equipment; adjust the centre controls; replace the main board
Horizontal or vertical linearity bad	Replace the main board
Abnormal or distorted raster	Move the display away from interference; do the geometry adjustments; replace the main board; the CRT (rarely required)
Whole raster tilted	Move the display away from interference; do the geometry adjustments; do the yoke adjustment; replace the main board
Picture breaks into diagonal lines, rolls vertically, or breaks and rolls horizontally	Check the computer's video with a known-good monitor; replace the main board
Black raster with a single vertical or horizontal line	Replace the main board; the CRT
Raster too dark, too bright or washed out	Adjust contrast and brightness; check the computer's video; do the video adjustments; replace the main board; the CRT (rarely required)
Out of focus	Do the focus adjustment; replace the main board; turn the focus controls to their limits, and if one area stays out of focus, replace the CRT
Predominant colour tint	Check the video card; do the video adjustments; replace the main board; replace the CRT if a red, green or blue tint cannot be removed
Out of convergence (colour bleeding from text or lines)	Check the computer's video; do the convergence adjustments; replace the main board; the CRT
Picture jitters or flashes	Move the display away from interference; check that all ground cables are secure; replace the main board
Intermittent shut-down, flashing or wavy screen, high-pitched noise, no degauss	Replace the main board
Black spots on the screen (burnt phosphor)	Replace the CRT
Erratic or no communication with an ADB device	Replace the keyboard cable, keyboard, mouse or other ADB device

Not a fault

A thin horizontal line about one third of the way up the picture is the aperture grille's support wire, which Apple says is present on all Trinitron displays smaller than 15 inches. It cannot be adjusted out or removed by replacing modules.

Notes

• Apple's specification allows 20 minutes of warm-up before the display meets all its figures, and the cutoff and white balance procedures need at least 10 minutes. Judge colour and focus on a warm display.
• Apple's main board was supplied in three versions (661-0102 with Energy Star, 661-1650 without, 661-0169 Rev. B).
• The Service Source contains no component-level information. A low-resolution scan of an M1212 schematic is hosted as File:Macintosh Color Display M1212 Schematic.pdf.

Related pages

• Apple Macintosh Color Display
• Apple Macintosh Color Display General Maintenance
• Macintosh Color Display Service Source
• Capacitor Failure Symptoms