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IMPORTANT
IMPORTANT
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
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
Cal: An
Overview") and stored on a disk for access by the end user.
Chapter 9
page 120
for contact information.
Service
Troubleshooting
"Test Set
137
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