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1780R-Series Service Manual
1–1
Product Description
The Tektronix 1780R-Series Video Measurement Set is a 19-inch wide,
5 1/4-inch high, 18-inch deep dual-CRT Waveform Monitor/Vectorscope. It
weighs approximately 28 pounds and is intended for rack-mount applications,
but can also be configured as a full (rack) width cabinet model for bench and
portable applications. See Figure 1–1. The remainder of the front-panel area
contains controls and switches that manually configure the instrument for
measurements. Both CRTs have alphanumeric readout and touch-screen control
to simplify measurement tasks and operating menus.
Figure 1–1: Simplified representation of the 1780R-Series Video Measurement Set
The left CRT is selectively used for vectorscope, picture monitor, SCH phase,
and XY displays, while the right one is used for the waveform monitor displays.
The picture monitor display has a bright-up strobe; when the instrument is in a
line select mode, that makes its display identical to that of a picture monitor
driven from the rear-panel Pix Mon Out.
The right CRT is used for the normal filtered waveform monitor displays.
Waveform monitor measurements can have voltage and time cursors added to the
display to improve measurement accuracy. The elapsed time or amplitude
difference between cursors is displayed as alphanumeric CRT readout. Besides
the typical waveform monitor displays the right CRT is used for high-resolution,
high-accuracy differential gain and phase measurements.
Signal and reference input is through 75 W bridging loop-through inputs. There
are four composite video inputs, making it possible to use the 1780R-Series to
measure analog component signals, if desired. In addition to the normal 1- or
2-line, and 1- or 2-field displays, both component and composite signals can be
displayed in parade or overlay mode. The external reference can be either
composite sync or black burst. The 1780R-Series can also be operated with an
external subcarrier reference input, similar to the Tektronix 520-Series.
All instruments in the series have a front-panel, high impedance (1 MW) probe
input. Signals input through the probe can be displayed as single or multiple
lines or fields and can also be overlayed or paraded with the rear-panel input