Sheet 3 Circuit Functions; Backplane Board Schematic; Exploded View Diagram - Agilent Technologies 66000A Service Manual

Mps mainframe

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Power to the mainframe is provided by a switching power supply. Energy is stored in the magnetic field of transformer T1

when current flows in the primary, and is transferred to the secondary side when the current flow in the primary is turned

off. Primary current flow is controlled by FET switches, which are turned on and off at an 85KHz rate by U1.

Regulation is accomplished by controlling the on-time of the FET switches. U1 monitors the voltage at the secondary side of

T1 through opto-isolator U2 and adjusts the on-time of the FETs accordingly. T2 provides bias power for U1.

Power at the secondary side of T1 is rectified and filtered to provide +5V power to the mainframe and +5V and +28V

power to the turn-on circuits in the modules.

Sheet 3 Circuit Functions

Among the circuit components included on Sheet 1 are: multiplexers U71 and U72, demultiplexers U74 and U87, power-on

chip U68, Trigger In/Out BNC connectors J116 and J117, and DFI/RI connector TB2.

The multiplexers and demultiplexers direct the digital signals from the microprocessor and distribute them among the eight

module slot locations via J121 and J122. +5V and +28V bias power is distributed to the module slot locations via J120. U68

generates a power-on (power is available) signal to the module slot locations via J120.

Note

J120 connects to J10 on the Backplane board, J121 connects to J9 on the Backplane board, and J122

connects to J11 on the Backplane board.

The Trig IN signal from J117 is distributed to the module slot locations via J120. The Trig OUT signal to J116 is directly

received from the module slot locations via J120. The RI (remote inhibit) signal from TB2 is processed by U44. U44 also

generates the DFI (discreet fault indicator), which is connected to TB2 via opto-isolator U64.

SHOCK HAZARD When servicing the Main assembly and Backplane assembly, ac line voltages are

present on the Main board and backplane connectors.

The Backplane board schematic shows the distribution of the ac power and control signals from the Main board to the eight

module connectors. There are no active components on the Backplane board.

The exploded view diagram at the end of this section documents how the major components of the Agilent 66000A MPS

Mainframe are assembled. Parts with "MP" designations identify components that are referenced in the parts list. Refer to

Chapter 5 for the part number and description of the mechanical parts.

40 Diagrams

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