Installation guide

Troubleshooting
Getting Started with Troubleshooting
1-5
ILT-2 A12 CPU Power-On Test
A12 CPU Power-On Test
At power-on, the A12 CPU is designed to complete a series of operational checks. If all power supply voltages
are present and the A12 CPU is working correctly, the operational checks are completed. Errors are reported
if the A12 CPU has problems identifying other assemblies.
Failure Symptoms
• A2 Display is not functioning
• A12 CPU fails to complete the power-on check
• no LAN activity
• no signal generator control from the front panel
• error message is displayed after power-on
A2 Display is Not Functioning
Refer to ILT3 Front Panel Display Troubleshooting on page 1-9.
A12 CPU Fails to Complete the Power-On Check
1. Turn the power off and remove outer and inner covers.
2. Turn the power on and verify that LEDs DS18 through DS25 of the A12 CPU are on.
(Refer to Figure 1-1 for the location of LEDs DS18 through DS25 of the A12 CPU.)
• If any of the LEDs are off, turn the signal generator on its side
and check the voltages in Table 1-3 at the A23 Motherboard.
• If the voltages are not present on connector J15 and J5 of the A23 Motherboard,
refer to “Power Supplies” on page 1-23.
• If the voltages are present on connector J15 and J5 of the A23 Motherboard,
turn the power off and remove the A12 CPU.
3. Use a DVM and ohm out J15 to J8 and J5 to J7.
• If the connector is open, change the A23 Motherboard.
• If the connector ohms out good, change the A12 CPU.