Agilent Technologies E3631A manual Bias Supplies Problems

Chapter 5 Service

Troubleshooting Hints

Bias Supplies Problems

Check that the input to the voltage regulators of the bias supplies is at least 1 V greater than their output.

Circuit failures can cause heavy loads of the bias supplies which may pull down the regulator output voltages.

Check the voltages of bias supplies as tabulated below.

Table 5-1. Bias Supplies Voltages

Bias Supply	Minimum	Maximum	Check At
+5V Floating	4.75 V	5.25 V	U1 pin 2 (on the top Board)
-5.1V Floating	-4.75 V	-5.25 V	Anode of VR4 (on the top Board)
+15V Floating (±25V supplies)	14.25 V	15.75 V	Cathode of CR16 (on the top Board)
-15V Floating (±25V supplies)	-14.25 V	-15.75 V	Anode of CR18 (on the top Board)
+15 Floating (+6V supplies)	14.25 V	15.75 V	U25 pin 2 (on the bottom Board)
-15 Floating (+6V supplies)	-14.25 V	-15.75	U24 pin 3 (on the bottom Board)
+5V Ground Ref.	4.75 V	5.25 V	U11 pin 3 (on the bottom Board)

Some circuits produce their own local bias supplies from the main bias supplies. Be sure to check that these local bias supplies are active. In particular, the ADC (analog-to-digital converter), ac input, and front panel sections have local bias supplies. Always check that the power supplies are free of ac oscillations using an oscilloscope. Failure of bias supplies will cause many self- test failures.

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