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1780R-Series Service Manual
3–1
Theory of Operation
Contents of this section are designed to work with the block and schematic
diagrams in Section 9, at the back of this manual. Each schematic diagram
description begins with a small block diagram of the circuits on that page and a
short overview relating the illustration to the circuit theory that follows.
Block Diagrams
The 1780R-Series contains a large amount of circuitry; in order to simplify the
block diagram, it has been split into 5 pages. Each page covers a specific area of
operation. Symbols used on these diagrams are those that have typical use in
instruction manuals for other Tektronix television instruments. In particular:
A number in brackets (< >) denotes the schematic diagram (in Section 9)
where that individual circuit can be found.
Names within the dashed line rectangles are switching functions that are
either activated by front-panel switches or touch-panel menu selections.
Input and output signals that go to another block diagram are identified both
by signal name and the name and number of the block diagram they are
going to or coming from.
For example, –REF H SYNC MPU 4 is the reference horizontal sync and is
shown going to the Microprocessor, which is shown on Block Diagram
number 4.
This diagram contains all of the signal input circuitry, DC restorers, signal filters,
and the vertical amplifiers and output for the waveform monitor.
This diagram contains the sync separators (input and reference), ramp generators
(including slow sweep), output amplifiers for the horizontal sweeps, clamp pulse
generator, and SCH identification and output circuits.
This diagram has the vectorscope amplifiers, timing circuits, demodulators, and
output circuits. In addition, the subcarrier regenerator, precision phase shifter, dP
and dG demodulators, digital recursive filter, X-Y, and picture monitor sweeps
also appear here.
Block Diagram 1
Input And Waveform
Vertical
Block Diagram 2
SCH And Waveform
Horizontal
Block Diagram 3
Vectorscope