228 Chapter4
Troubleshooting the Analyzer
Troubleshooting the A2 Display Assembly
WARNING High voltage is present within the A2 display and remains for
some time after it has been disconnected. Be careful while
troubleshooting the display outside of its enclosure.
If an A2 display assembly failure is suspected, the display must be
removed from its enclosure for further troubleshooting. Refer to the A2
display assembly removal procedure in Chapter 3 before checking the
continuity of the W2 and W3 wire harnesses. If both W2 and W3 are
good, suspect the A2 display.
The A2 display is not field-repairable, and must be replaced as an
assembly. Refer to Chapter 10 for part number information.
After replacement, adjust the new display, refer to step 2.
If the display has an intensity problem
CAUTION The A1R1 potentiometer leads are easily broken. Do not twist the W3
wire harness where it attaches to A1R1.
1. Disconnect W3 from the A1R1 intensity control potentiometer on the
front frame.
2. Check the continuity and resistance range (0 to 100 kΩ) of the inner
potentiometer on A1R1.
3. Reconnect W3 to A1R1.
If the display is blank
1. Verify the MONITOR OUTPUT, located on the analyzer rear frame,
by performing the following:
• Attach an external monitor to the MONITOR OUTPUT
connector. The MONITOR OUTPUT is a NTSC composite video
with horizontal at 15.75 kHz and a vertical rate of 60 Hz.
• Adjust the horizontal hold on the external monitor, if necessary.
If a normal instrument display is present, the display failure is
limited to the A2 display and its related circuitry.
2. Verify the output of the drive circuitry from the A16 processor/video
assembly to the A2 display by performing the following steps.
• Position the analyzer with the bottom side facing up.
CAUTION Do not short any two of the A16J8 pins together. Damage to the output
buffer amplifiers located on the processor/video assembly may occur.
• Disconnect the W2 wire harness.
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