
The 5 volt earth referenced supply (+5V_ER) is produced by rectifier
CR101, CR102, CR103, CR104, and regulator U101. This supply is
earth referenced by the screw which mounts the PC board to the
instrument chassis.
The unsw5V_ER supplies U305, U303, U320, and U302.
The rear-panel interfaces (GPIB, RS-232, Alarms, and external
triggers) are powered from the sw5V_BP supply to ensure
that when power is turned off no voltages are present at the interfaces.
The +5V_ER supply is switched by Q101A and Q101B to create the
+5V_BP (backplane) and fan power supplies.
Undervoltage sensor U102 provides the earth reference controller
reset at initial power on.
Chapter 5 Theory of Operation
Power Supplies
126
Summary of Contents for 34970A
Page 1: ...Agilent 34970A Data Acquisition Switch Unit Service Guide ...
Page 34: ...32 ...
Page 35: ...2 Quick Start 2 ...
Page 49: ...3 Front Panel Overview 3 ...
Page 62: ...60 ...
Page 63: ...4 Calibration Procedures 4 ...
Page 118: ...116 ...
Page 119: ...5 Theory of Operation 5 ...
Page 159: ...6 Service 6 ...
Page 177: ...General Disassembly 4 3 2 1 6 Chapter 6 Service Disassembly 175 ...
Page 178: ...Internal DMM Disassembly 3 2 1 Chapter 6 Service Disassembly 176 ...
Page 180: ...Additional Chassis Disassembly 1 2 Chapter 6 Service Disassembly 178 ...
Page 181: ...Plug In Module Disassembly Needle nose Pliers 6 Chapter 6 Service Disassembly 179 ...
Page 182: ...180 ...
Page 183: ...7 Replaceable Parts 7 ...
Page 220: ...Chapter 7 Replaceable Parts Manufacturer s List 218 ...
Page 221: ...8 Schematics 8 ...
Page 272: ......