Service manual

126 5
Power Supply Troubleshooting
FIND OUT WHY THE FAN IS NOT ROTATING
Figure 5-7 A40 Output Voltage
3. Check the A50 SHUTDOWN LED
When the fan stops, the A50 SHUTDOWN LED is off. The fan generates a FAN LOCK
signal. The signal is fed into the FAN LOCK SENSE circuit in the A50 DC-DC converter.
If the FAN stops, the FAN LOCK signal is missing. Then the FAN LOCK SENSE circuit
activates the A50 shutdown circuitry, resulting the SHUTDOWN LED being turned off.
Perform the following procedure to check that the A50 SHUTDOWN LED is on.
1. Turn the analyzer power on.
2. Look at the A50 SHUTDOWN LED. The LED location is shown in Figure 5-2.
• If the SHUTDOWN LED is on, replace the A50 DC-DC Converter.
• If the SHUTDOWN LED is off, continue with the TROUBLESHOOT THE FAN
AND THE A50 DC-DC Converter section in this chapter.