24 Impedance Analyzer
1 Troubleshooting
Step 1.   Check fan operation and DC monitor LED.
If the rear panel fan (blower) doesn’t run, a failure in power supply 
is assumed. Remove the E4990A outer cover and check if the 
following LEDs light:
• +3.3 V and +5 V DC monitor LEDs on A60 CPU module as shown 
in Figure 4.
• LEDs on A51 DSP module as shown in Figure 5.
Figure 4 LEDs on CPU module
Figure 5 LEDs on DSP module