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Apple ColorSync Display 17 Troubleshooting Guide

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AppleVision 750 Display (Ben Boldt, Wikimedia Commons, public domain)

Fault-finding on the Apple ColorSync Display 17 (AppleVision 750 and 750AV) from Apple's Service Source. Apple warns that many returned modules work, and asks for a 20-minute warm-up, Apple Display software 1.5.3 or later, and a known-good monitor that is not itself an AppleVision or ColorSync display, because two of them on one Mac can upset the software.[1]

Read CRT Discharge Procedure before opening the display; the anode runs at about 26 kV.

First checklist

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  • The display works with Macintosh and PC computers within 30-80 kHz horizontal and 40-120 Hz vertical; some computers need a video card. It works best at its factory-preset resolutions.
  • A raster is never a perfect rectangle, and colour purity is never perfect over the whole screen. Magnetised metal furniture causes bowing and colour blotches; if the picture changes when the display is moved, the environment is the cause.
  • Fluorescent lights, other monitors and electronic devices cause jitter and faint lines.
  • Misadjustment can mimic main deflection board or CRT failure.[1]

Symptom charts

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AppleVision 750/750AV symptom charts (Service Source pp. 4-10)
Symptom Cures, in order
No raster, power light on Check the computer's video with a known-good monitor, then reconnect the ColorSync display with video and ADB cables; raise brightness and contrast; check for high voltage (a rustle at switch-on or off means it is there), and if present, check the software and start up holding Command-Option-A-V to run the built-in recovery; replace the main deflection board; replace the CRT/video board where supported
No raster, power light off Check power, the power button, the computer and the ADB and video cables; check internal cables and that the CRT/video board is seated on the CRT socket; replace the main deflection board; the CRT/video board where supported
Black screen after a restart Switch the display off and on (no permanent damage); replace the main deflection board
Raster shape distorted Adjust in the Monitors & Sound control panel, using Factory Settings if needed
One predominant colour Check the CRT/video board on the CRT socket; Recalibrate in Monitors & Sound; start up holding Command-Option-A-V; replace the CRT/video board where supported
Rainbow bands of colour Degauss with a manual degaussing coil; replace the main deflection board; the CRT/video board where supported
Very bright screen (may shut down) Recalibrate; Command-Option-A-V at startup; replace the main deflection board; the CRT/video board where supported
Poor focus Check convergence first (bad convergence looks like bad focus); adjust H and V focus on the flyback with the focus pattern; check the red and white wires in the CRT socket; replace the main deflection board; the CRT/video board where supported
Centre still blurred after focus Adjust H-Stat (lower left of the CRT/video board); for blurred top and bottom, adjust top and bottom convergence (back of the board); check the CRT socket wires
750AV microphone does not work Try the microphone on another 750AV; with it unplugged, the microphone connector inside the bezel, and connector BA10 on the sound board, should read 8 V DC

[2]

Apple lists these as typical symptoms of a defective 750AV sound enclosure: no sound on one channel, no recording, no volume, bass or treble control, distortion, no gain control, loud popping and silent headphones. It adds that speakers, the microphone and their cables can cause some of them.[2]

Hardware diagnosis

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If the Display Service Utility cannot talk to the display, measure between chassis ground and the end of resistor RL1 (390 Ω) nearest capacitor CP17 on the main deflection board. A reading of 11.5-12.5 V points to the CRT/video board; anything else points to the main deflection board.[3]

The anode check uses Apple's probe 076-0392 under the anode cap and should read 26 V DC (26 kV); 0 V means the main deflection board.[4]

Not faults

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  • The two thin horizontal lines are the aperture grille's support wires.[2]
  • Jitter or blur with a Power Macintosh 5500 (TY705-TY715) or 6500 (XB708-XB723) is a fault in the computer; the 6500 should not be set above 1152 × 870.[5]
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References

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  1. ↑ 1.0 1.1 Apple Computer, 17" ColorSync Displays (Service Source), Troubleshooting, First Checklist and Symptom Charts, pp. 2-4 (PDF pp. 37-39). Hosted here: File:colorsync_17_displays.pdf (see 17" ColorSync Displays Service Source).
  2. ↑ 2.0 2.1 2.2 17" ColorSync Displays Service Source, Troubleshooting, Symptom Charts, pp. 4-10 (PDF pp. 39-45).
  3. ↑ 17" ColorSync Displays Service Source, Troubleshooting, Diagnosing a Suspected Hardware Problem, pp. 18-21 (PDF pp. 53-56).
  4. ↑ 17" ColorSync Displays Service Source, Troubleshooting, Checking High Voltage, p. 17 (PDF p. 52).
  5. ↑ 17" ColorSync Displays Service Source, Hot Issues, pp. 1-6 (PDF pp. 3-8).


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