Chapter 12 631
Display/Power Supply Section
Blanking Signal
Blanking Signal
1. Connect an oscilloscope probe to A2J202 pin 3. Connect the
oscilloscope ground lead to TP3. Set the oscilloscope to the following
settings:
Sweep time ................................................................ 2ms/div
Vertical scale 1 V/div
2. If a 4 Vp-p signal is not observed, the A2 controller assembly is
faulty.
3. Repeat steps 1 and 2 with the oscilloscope probe on A2J202 pin 14.
4. Set the oscilloscope to the following settings:
5. Connect the positive probe lead to A2J202 pin 15. This is the
blanking output.
6. TTL-level pulses should be observed. If the signal is either always
high or always low, the display will be blanked; suspect the A2
controller assembly.
7. If the signals on A2J202 pins 3, 14, and 15 are correct, troubleshoot
the A17 CRT driver.
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