E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
A18 CPU Turn–On Test
1-3
a. Instrument Info/Help Mode
b. Self Test
c. Run Complete Self Test
3. When the Self–Test finishes, one of the following messages displays:
• If the Self Test passed: “The current status of self test is: Success All self tests have passed.”
• If the Self–Test failed: “The current status of self test is: Failed.” The message also reports the most
independent failure.
4. If the Self–Test failed, look up the reported most independent failure in the “Self–Test Failures and Related
Troubleshooting” section on page 1- 6.
5. Troubleshoot and repair the most independent failure.
6. After you replace the failed assembly, run the Self–Test again.
7. If another assembly is reported as the most independent failure, repeat steps 4 thru 6 until the Self–Test passes.
A18 CPU Turn–On Test
NOTE If it is determined that the A18 CPU is defective but still functions, it is recommended that you back up the
calibration data in the CPU prior to replacing it. To back up the calibration data, see “CPU Data Backup” on
page 1- 5.
At turn–on, the A18 CPU is designed to complete a series of operational checks. If all power supply voltages are
present and the A18 CPU is working correctly, the operational checks are completed. Errors are reported if the
A18 CPU has problems identifying other assemblies or communicating with the backup memory located on the
A31 Motherboard.
Failure Symptoms
• display is not functioning
• CPU fails to complete the turn–on check and does not reach normal LCD operation
• display is not functioning after turn–on
• unable to control signal generator from front panel
• error message is displayed after turn–on
A2 Display Not Functioning or A2 Display Not Functioning After Turn–on
Refer to “Front–Panel Display Assembly Troubleshooting” on page 1- 10.
A18 CPU Fails to Complete the Turn–On Check
1. Turn power off and remove outer and inner covers.
2. Turn on power and verify A18 CPU LED DS9 (+3.4 Vdc) and DS10 (+5.2 Vdc) are on. If either of the LEDs are off,
check the voltages in Table 1- 2. Refer to the illustration in “Self–Tests 11xx: A18 CPU Self–Test Errors” on
page 1- 45 for LED locations.
3. If the voltages are present on connector P222, turn power off and remove the A18 CPU.
4. Inspect the pins on the A31 Motherboard connector. If the pins look good replace the A18 CPU.
5. If either of the voltages are missing, refer to “Power Supply Troubleshooting” on page 1- 14.
Tab l e 1 - 2
Connector P222
(A31 Motherboard)
Supply Voltage Acceptable Range
Pin 45–48, 95–98 +3.4 Vdc +3.4 ± 0.07 Vdc
Pin 49, 50, 99, 100 +5.2 Vdc +5.2 ± 0.1 Vdc
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