Sweep Generator; Pickoff Comparators And Delay Gate Generator; Logic; Digital Voltmeter - Tektronix 7B15 Instruction Manual

This section of the manual describes the circuitry in the
71315 Delaying Time-Base unit . The description begins
with a discussion of the instrument, using the block
diagram shown in Figure 3-1 . The circuit diagrams at the
rear of this manual are blocked off according to circuit
The following discussion is provided to aid in
understanding the overall concept of the 71315 before the
individual circuits are discussed in detail . A basic block
diagram is shown in Figure 3-1 . The numbered diamond
in each block refers to the corresponding circuit diagram
at the rear of this manual .
The Trigger Generator ensures a stable crt display by
starting each sweep at the same point on the waveform .
Circuitry is included for selection of trigger mode,
coupling, and source . The output of the Trigger Generator
is a fast-rise gate which enables the Sweep Generator.
The sweep sawtooth signal is initiated when the Trigger
Generator output is applied to the Sweep Generator. The
rate of change (slope) of the sawtooth signal is
determined by the TIME/DIV
switch setting. The
sawtooth signal provides horizontal deflection for the
mainframe (oscilloscope) and is used by the Pickoff
Amplifiers and the Delay Gate Generator in the 7815 .
The Sweep Generator also generates a Sweep Gate
pulse which unblanks the crt in the mainframe.
IGGE GENERATOR
SWEEP GENERATOR
function . These circuit block titles serve as indexes to the
circuit discussion . Refer to the appropriate diagram along
with the Troubleshooting Chart in the Diagrams and
Circuit Board Illustrations when reading this discussion .
Section 3---71315
PICKOFF COMPARATORS AND
DELAY GATE GENERATOR
The Pickoff Comparators and Delay Gate Generator
circuits produce a delay gate when the sawtooth signal
from the sweep generator reaches the level set by the
DELAY TIME and /-\ 'TIME controls . The DELAY 'TIME
control
determines the pickoff point for the first
intensified zone and the A TIME control determines the
pickoff point for the second intensified zone . The Delay
Gate signal enables the companion delayed time-base
unit .
LOGIC
The Logic circuit determines the sweep mode (B DELAY
MODE) of the 71315 . The 71315 can operate either
independently or delay a companion delayed sweep time-
base unit . The Logic circuit also determines the trigger
mode and generates control signals for use by the
mainframe (e .g ., hold off, auxiliary Y-axis, etc.) .
DIGITAL VOLTMETER
The Digital Voltmeter circuit converts the selected do
pickoff levels (from the Pickoff Comparators) to a
calibrated delay-time readout on the crt. When operating
in the DELAY TIME mode, the time before the start of the
first intensified zone is displayed on the crt readout;
when operating in the A TIME mode, the differential time
between the start of the first intensified zone and the
second intensified zone is displayed.