5Service
118 Keysight E3633A and E3634A Service Guide
Unit fails self-test
Verify that the correct power-line voltage setting is selected. Also, ensure that all
terminal connections are removed while the self-test is performed. Failure of the
DAC U22
[1]
on the PC board will cause many self-test failures.
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.
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.
[1] For serial MY53xx6xxx, failure of the DAC U104 on the PC board will cause many self-test failures.
Table 5-1 Bias supplies voltages
Bias Supply Minimum Maximum Check At
+5 V Floating +4.75 V +5.25 V U10 pin 2
-5.1 V Floating -4.75 V -5.25 V Anode of CR6
+15 V Floating +14.25 V +15.75 V Anode of CR9
-15 V Floating -14.25 V -15.75 V Cathode of CR10
Table 5-2 Bias supplies voltages
Bias Supply Minimum Maximum Check At
+3.3 V Floating +3.135 V +3.465 V U203 pin 3
+15 V Floating +14.25 V +15.75 V Anode of CR202
-15 V Floating -14.25 V -15.75 V Cathode of CR203
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