Keysight E3632A, Service Manual

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2 Service
66 Keysight E3632A Service Guide
DAC U21
[1]
on the top 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.
Table 2-1 Bias supplies voltages
Table 2-2 Bias supplies voltages (serial MY53xx6xxx)
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 U36 on the top board will cause many self-test failures.
Bias supply Minimum Maximum Check at
+5 V Floating +4.75 V +5.25 V U11 pin 2
–5.1 V Floating –4.75 V –5.25 V Anode of CR5
+15 V Floating +14.25 V +15.75 V Anode of CR9
–15 V Floating –14.25 V –15.75 V Cathode of CR10
Bias supply Minimum Maximum Check at
+3.3 V Floating +3.135 V +3.465 V U23 pin 3
+15 V Floating +14.25 V +15.75 V Anode of CR7
–15 V Floating –14.25 V –15.75 V Cathode of CR23