Keysight E3631A, Service Manual

Page: 117 / 131

Service 5
Keysight E3631A Service Guide 113
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)
+15V Floating (+6V
supplies)
14.25 V 15.75 V
U25 pin 2 (on the bottom
Board)
-15V 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)