IMPORTANT
IMPORTANT
Service
Troubleshooting
If the power supply voltage is measured while the cable is disconnected from the main board assembly, the +5 volt supply may not function. It requires a load of at least 0.5 amps to operate properly. This can be simulated with any 10 ohm, 5 watt resistor.
The LEDs on the main board assembly indicate that power is being received. The fan operates from +12 volts and has its own regulator derived from the +15 volt supply. If the fan does not operate, check the +12 volt supply at test point TP706.
The LED Display Board
If all performance tests pass, but the LED indicators on the front panel do not operate, then the most likely cause of failure is the LED display board assembly or its associated ribbon cable.
The Main Switch Board Assembly
If any of the performance tests fail and the cause is not obvious, such as a bad power supply, damaged or loose connector, etc., then the recommended course of action is to replace the main board assembly.
Do not remove or adjust the shields on the main switch board assembly. The placement of shields and gaskets on the assembly is critical to the performance of the test set. Changes should only be made at the factory.
If the main board assembly is replaced, it is critical that the socketed ID ROM (U801) be transferred from the old board assembly to the new one. The replacement board assembly will not contain an ID ROM when purchased, and will not function properly without this ROM. In the unlikely case that this ROM should fail, contact Agilent Technologies. See page 120 for contact information.
Post-Repair Procedure
If the main board assembly or power supply is replaced, a complete performance test should be performed. A Test Set Cal should be performed also (see “Test Set Cal: An Overview”) and stored on a disk for access by the end user.
Chapter 9 | 137 |
