Apple Multiple Scan 20 Display Specifications download pdf (Page 20)

Troubleshooting Symptom Charts/No Raster - 4

Symptom Charts

No Raster

No raster (screen is

black); power

indicator light on

1 Ensure that the display is connected to a known-good video

source.

2 Adjust the front panel brightness and contrast controls.

3 Check the monitor’s video cable for breakage or damage.

Perform a continuity check to ensure that the video cable is

not at fault.

4 Slowly adjust the screen control on the flyback transformer

to see if the raster appears. If it reappears, perform the

“Cutoff and White Balance” procedure in the Adjustments

chapter.

5 Replace the main deflection board.

No raster; power

indicator light off

1 Ensure that the display is plugged in and that the power cord

is not damaged.

2 Replace the main deflection board.

Video

Display has one

predominant color

1 Verify that the CRT/video board is connected securely to the

CRT socket.

2 Inspect the video cable connector (at P301) on the CRT/

video board for breakage/continuity. This cable carries the

Red, Green, and Blue signals from the main deflection board

to the CRT/video board.

3 Perform the “Cutoff and White Balance” procedure in the

Adjustments chapter.

4 Replace the CRT/video board.

5 If you suspect a defective CRT, contact Apple Technical

Support.

P301

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Apple Multiple Scan 20 Display Specifications Page 20