Service and Maintenance 8
E364xA User’s and Service Guide 195
Some circuits produce their own local bias supplies from the main bias supplies.
Check that these local bias supplies are active. In particular, the analog-to-digital
converter (ADC), 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.
Table 8-1 Bias supplies voltages
Bias supply Minimum Maximum Check at
+5 V floating +4.75 V +5.25 V U110 pin 2
–5.1 V floating –4.75 V -5.25 V Anode of CR114
+15 V floating +14.25 V +15.75 V Anode of CR104
–15 V floating -14.25 V -15.75 V Cathode of CR105
Table 8-2 Bias supplies voltages (serial MY53xx6xxx)
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 CR104
-15 V floating –14.25 V –15.75 V Cathode of CR105
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