Fluke 5220A Instruction Manual page 33

The A4 Regulator is designed to convert the ac outputs from the three remaining
secondary windings of T1 into three sets of isolated and regulated voltages: +5 V dc,
+15/-15 V dc, and +5 V dc ISO (isolated). Each voltage is produced using conventional
regulating techniques. That is, it is rectified, filtered, regulated by a three-terminal
regulator, and filtered again before being output. A fifth voltage, Line Mon (monitor), is
also produced on the A4 Regulator. It is derived from the T1 windings used for the
+15/-15 V dc supply and is used to convey the line power status of the 5220A to the A10
Logic. The voltage is rectified by diodes CR8 and CR9, and clipped by zener VR1 before
being output.
Figure 3-3. Power Supply Functional Block Diagram
Theory of Operation
Circuit Analysis
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