User`s guide

6-24 User’s and Service Guide
Service
Theory of Operation
Theory of Operation
The theory of operation begins with a general description of the 87050A
Option K24 multiport test set. This is followed by more detailed
operating theory. The operation of each group is described briefly, to the
assembly level only. Detailed component level circuit theory is not
provided.
System Theory
The test set consists of three main components: a power supply, a front
panel display, and a controller interface mother board. The purpose of
the power supply is to provide power to both the front panel display and
the main switch board. The front panel display serves to indicate the
switching paths to the user. Finally, the controller interface mother
board does the actual switching between the different ports.
A1 Power Supply Theory
The switching power supply provides regulated dc voltages to power all
assemblies in the test set. A dc cable provides power to the main switch
board. A connector from the main switch board to the front panel
display provides dc power and control signals to the front panel. The
power supply provides the following voltages: +24V, +12V, and +5V.
The power LED on the front panel indicates that the instrument is on
and that the power supply is providing power.
A2 Front Panel Display Theory
The front panel display consists of an LCD. The LCD is divided into two
lines, forward and reverse. The first line indicates which of the 24 ports
is connected to the forward path. The second line indicates which of the
24 ports is connected to the reverse path. Control signals and dc power
are provided by a cable connected to the main switch board.