Apple Multiple Scan 1705 Display Troubleshooting Guide

Apple Multiple Scan 1705 Display (Apple Service Source)

Fault-finding on the Apple Multiple Scan 1705 Display from Apple's Service Source: the first checklist, the symptom charts, the high-voltage check and the no-raster flowchart. Read CRT Discharge Procedure before opening the case; the anode runs at 25 kV.

First checklist

Apple warns that many returned modules work. Before changing anything:

• Check that the computer is within the display's range: 31-65 kHz horizontal and 47-120 Hz vertical. Some computers need a video card.
• Expect some distortion; move the display away from magnetised metal furniture if the edges bow.
• Jitter, faint lines and movement often come from electronic devices and fluorescent lights; try another room.
• A misadjusted picture can mimic deflection board or CRT failure. CRTs rarely fail.

Symptom charts

Apple Multiple Scan 1705 Display symptom charts (Service Source pp. 5-13)

Symptom	Cures, in order
No raster, LED on	Check the cable and tighten the thumbscrews (to the video card if one is used); adjust brightness and contrast; a screen saver or Energy Saver may be active (the display wakes in about 20 seconds); some Macintosh models do not wake from Energy Saver, so restart and disable it; check the high voltage
No raster, LED off	Check the power cord and the wall outlet; check that the computer is on; check the video cable; replace the video and main deflection boards and adjust cutoff and white balance; send the monitor to Apple
No raster, LED yellow	Check the video cable; see "Do You Need a Video Card" in the user's manual
Screen flickers	Check the cable; move the monitor; keep monitors at least 18 inches apart; with a video card, raise the refresh rate above 60 Hz; replace the video and main deflection boards
Screen blurred	Adjust focus at VR F1 and F2; replace the video and main deflection boards
Raster too bright	Adjust brightness; adjust cutoff and white balance; replace the video and main deflection boards
Colours too green, red or blue; unreadable	Check the computer's video with a known-good monitor; check the cable; adjust cutoff and white balance; replace the video and main deflection boards
No colour	Check the number of colours in the Monitors control panel
Raster too short, tall, narrow or wide	Adjust width and height; replace the video and main deflection boards
Raster not centred	Move the monitor; adjust the user centre controls; adjust raster centre at VR701; replace the video and main deflection boards
Indicator light goes out before adjustment is finished	Normal: the LED goes out after 10 seconds by design

Every board replacement is followed by the cutoff and white balance adjustment.

High voltage and no-raster flowchart

With the rear housing and EMI shield off, Apple's high-voltage probe (076-0392) under the anode connector should read 25 V DC on the meter, meaning 25 kV. Leave the probe in place until the display is off and unplugged.

Apple's flowchart then runs:

1. High voltage not 25 kV: replace the main deflection board, CRT/video board and rear fence, then adjust cutoff and white balance.
2. High voltage correct: set the meter to DC, ground lead on the frame, and measure CRT socket pin H. It should read about 6 V DC. If it does, check the computer and video card.
3. If pin H is wrong, measure pin 8 (labelled 6.3V). If pin 8 reads about 6 V, replace the boards. If it does not, check the video interconnect cable and connectors P702, P703 and P302: replace the cable if they are faulty, or the boards if they are good.
4. If pin H is right and the computer and video card are good, turn the screen control on the flyback slowly clockwise. If a raster appears, adjust cutoff and white balance; if not, replace the boards.

Related pages

• Apple Multiple Scan 1705 Display
• Apple Multiple Scan 1705 Display General Maintenance
• Apple Multiple Scan 1705 Service Source
• Capacitor Failure Symptoms