HP 54540 Series - Power Supply Assembly

Theory of Operation
This guide supports troubleshooting to assembly level. Theory of operation for the
main assembly is included as additional information. It is not comprehensive enough
for component-level troubleshooting. The main body of following theory describes
the HP 54542A. Differences in the other family models is covered at the end of the
acquisition section.
Block-Level Theory
The HP 54542A Oscilloscope has four channels which are individually sampled at 2 GSa/s.
Each channel is stored into 32 Kbytes of memory. The other instruments in this family have
reduced specifications or features. The front panel provides:
e Several dedicated knobs and pushbuttons for major oscilloscope functions.
e Single-function keys, multifunction keys, and a knob for the remainder of instrument
control.
e A9Q-inch (diagonal) green phosphor CRT for information display.
e A31/2-inch flexible disk drive
e A connection for probe compensation.
The rear panel provides several connections:
e The line power input.
e Anauxiliary trigger input.
e The CRT intensity adjustment.
e An HP-IB connector for connection to a printer or controller.
e AnRS-232 connection
e Two outputs, one for dc calibration and one for ac calibration or trigger out.
e Two power connections for active probes.
A switch to protect the calibration factors.
The instrument consists of four major assemblies and four attenuators. Use the instrument
block diagram on the previous page for the following discussion.
Power Supply Assembly
The switching power supply provides 120 W (200 W maximum) for the instrument. The ac
input to the power supply is 115 V or 230 V, -25 to +15%. Maximum input power is 350 VA
maximum. The ac input frequency is 48 to 66 Hz.
Unfiltered voltages of +15 V, -15 V, +12 V, —12 V, +5.2 V, and -5.2 V are supplied to the main
assembly where they are filtered and distributed throughout the board and to other
assemblies. The +5.2 V is adjustable on the supply.
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