Troubleshooting The A16 Processor/Video Board Assembly - Agilent Technologies 8590 Series Service Manual

Troubleshooting the A16 Processor/Video
Board Assembly
After you have determined that the problem is caused by the A16
processor/video assembly, use the following procedures. The 8590 Series
Analyzers Component-Level Repair Service Guide is required to assist
with these procedures. Refer to
component-level service information.
If a signal cannot be displayed
If a signal cannot be displayed, and it has been determined that a
top-screen signal of two volts is present at VIDEO_IF, the problem may
be on the A16 processor/video board assembly.
1. Put 0 V into the video circuit, simulating a bottom-screen signal
level condition by setting the diagnostic to the ground reference
detector. Refer to
this chapter.
Use an oscilloscope to check for the following conditions. Refer to
Sheet 2 of 4 of the A16 processor/video board assembly
component-level information.
• Check for 0 V throughout the signal path through U201, U61,
U45, and U46.
• Check the offset by measuring the inverting and noninverting
pins on U201, U61, U45, and U46. The difference between both
measured values should not exceed 5 mV.
2. Replace any components with excess offset voltage.
3. Put 2 V into the video circuit, simulating a top-screen signal level
condition by setting the diagnostic to the 2 V reference detector.
Refer to "Verify the 2 V reference detector"
Use an oscilloscope to check for the following conditions. Refer to
Sheet 2 of 4 of the A16 processor/video board assembly
component-level information.
• Check for 2 V throughout the signal path through U201, U61,
U45, and U46.
• Check the offset by measuring the inverting and noninverting
pins on U201, U61, U45, and U46. The difference between both
measured values should not exceed 5 mV.
4. Replace any components with excess offset voltage.
Chapter 4

Troubleshooting the A16 Processor/Video Board Assembly

Chapter 13
"Verify the ground reference detector"
Troubleshooting the Analyzer
for a list of available
located in
located in this chapter.
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