Macintosh Displays Single Raster Line




PROBLEM DESCRIPTION: The Macintosh displays a single white
raster line. The line is usually positioned horizontally or
vertically across the screen.

BEFORE YOU START: Familarize yourself with Macintosh Technical
Procedures. ALWAYS DISCHARGE THE CRT TO THE "GROUND LUG". The
Macintosh uses an isolated ground. Performing a discharge to the
chassis will DESTROY the logic board!

CAUSE:  In most cases this is an indication of a faulty Power
Supply Board but there exists a possibility that more than one
module is defective.

CURE:  Replace the modules in the following order:

1. Replace the power supply and test. If the system is still
  inoperative
  perform Step 2.
2. Replace the Logic Board. If the system is still inoperative
  perform
  Step 3.
3. Replace the CRT. If the system is still inoperative perform
  Step 4.
4. Replace the Power Supply and the Logic board as a set.


Published Date: Feb 18, 2012