Tektronix 371B, Service Manual

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Theory of Operation
371B Service Manual
3-9
OFFSET AMPLITUDE control on the front panel determines the amplitude of
the steps.
The step generator current amplifier consists of a control signal latch circuit, a
relay driver circuit, and a current amplifier circuit. It transforms the output of the
1-2-5 ranging circuit (diagram 12) into current steps of various amplitudes to be
applied to the DUT. The STEP/OFFSET AMPLITUDE control on the front
panel determines the amplitude of the steps.
The vertical sense circuitry consists of a current sense circuit, 1-2-5 ranging
circuit, looping compensator circuit and control latch circuit. The vertical sense
circuitry measures the collector current of the DUT, excluding stray capacitance
effects.
This circuitry consists of the voltage sense circuit, 1-2-5 ranging circuit, and
control latch circuit. It measures the collector voltage or base voltage of the
DUT.
This circuit consists of an interlock and overheat circuit, high-voltage control
circuit, high-current control circuit and high-voltage output circuit. The collector
supply interface and high voltage output controls the collector supply output,
step generator output and collector supply output relays by means of an
interlock.
The main key circuitry is located on the A11 Main Key board, and consists of
the bus buffer circuit, the address decoder circuit, the variable control circuit, and
the witch matrix circuit. These circuits interface signals between the A2 CPU
board and the A12 Sub Key board, and control set ups such as; VERTICAL
CURRENT/DIV, HORIZONTAL VOLTS/DIV and STEP/OFFSET AMPLI-
TUDE settings, and control focus.
The sub key circuit is located on the A12 Sub Key board, and consists of the
front panel display circuit and the front panel key matrix circuit. The circuit is
controlled by the A11 Main Key board; it displays the main key setting
information and transfers key input data from the key matrix.
This circuitry is located on the A14 Lower Key & FDD board, and consists of
the bus buffer circuit, the address decoder interface signals with the A2 CPU
board, set up collector supply VARIABLE settings, and transfer the status data to
the A2 CPU board.
Step Generator Current
Amplifier
Vertical Sense
Horizontal Sense
Collector Supply Interface
and HighĆVoltage Output
Main Key
Sub Key
Lower Key