Tektronix 1730 Series, Instruction Manual

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1730–Series Theory of Operation
4–4
When the RGB Parade display is enabled, the sweep is shortened and offset by
the RGB Staircase input signal, which produces three short ramps that are
displayed (in sequence) as a normal length sweep.
The output of the Mag Amplifier and the X component of the Readout (from the
Microcontroller) drive the Horizontal Output Amplifier, which matches
impedances and normalizes gain (approximately 100 V for a 10 cm sweep
length) in order to voltage drive the CRT horizontal deflection plates.
The blanking signal (from Line Select) and the Intensity and Readout voltages
are used by the Z-Axis Control to generate an unblanking signal for the CRT
during sweep time. When the sweep is magnified, the off-screen portion of the
sweep is blanked to increase the on-off contrast ratio. The Focus Amplifier,
which is controlled by the front-panel FOCUS control, provides a voltage to the
CRT focus ring.
Trace Rotation provides compensation for the magnetic field surrounding the
CRT. The CRT is of the Post Acceleration type, which requires a relatively high
potential difference between the cathode and post anode. The boost in 2
nd
anode
voltage is provided by an encapsulated 4X Multiplier. Trace Rotation provides
compensation for the magnetic field surrounding the CRT.
Vertical Input
Diagram 1
The video signal is input to the waveform monitor through amplifiers that can be
clamped at back porch time. Once buffered by the input amplifiers, whose gain
is –1, a Channel Switch selects the input to be filtered, drive the picture monitor
output, serve as the internal sync source, and eventually be displayed on the
CRT.
When an external reference (sync) source is used, the composite signal is input
through an ac-coupled amplifier, which also has a gain of –1. Selection of the
sync source is accomplished by a switch that is made up of a common base pair
and switching diodes. A clamped sync stripper is used to remove active video
information and regenerate a composite sync signal for use by time related
monitor circuits.
An accurate 100 kHz waveform from the Microcontroller is amplified and its
amplitude set and controlled by the Calibrator. Calibrator output is enabled and
output through the vertical amplifier low pass filter. The calibrator enable is also
generated by the Microprocessor.
CRT, Unblanking, and
High Voltage