Tektronix 455, Instruction Manual, Page: 116 / 246

Instrument O p tio n $ -4 5 5 /A 2 /B 2
CIRCUIT DESCRIPTION
BLOCK D IA G R A M SW ITCHING
Setting the A COUPLING switch to T V LIN E or T V FIELD
activates the sync separator circu it (see Fig. 1). The A
SOURCE switch determines the source o f the signal supplied
to the sync separator. The input signal passes through an
FET Input Buffer am plifier to an Inverting/Non-Inverting
A m plifier. Whether the am plifier is inverting or non-inverting
is determined by the setting o f the A SLOPE/SYNC switch.
The output o f the Inverting/Non-Inverting A m p lifie r is
supplied to the sync-separator circu it which strips the signal
o f video. The o utp ut o f the sync-separator circu it supplies
a composite-sync signal to the A and B trigger generators for
use as a trigger signal in the T V LIN E position o f the
A COUPLING and B SOURCE switches.
The output o f the sync-separator circu it is also supplied to
the vertical sync recognizer circuit. The vertical sync recog­
nizer circuit processes the composite-sync signal and supplies
a vertical-sync signal to the A trigger generator fo r use in the
T V Field position o f the A COUPLING switch.
In the AC, LF REJ, HF REJ, and DC positions o f the
A COUPLING Switch, —5 volts is connected to the base of
U2232E. This holds o ff U2232E, which holds o ff U2232A
and U2232B. Therefore, the sync separator is inoperative.
In the T V FIELD and T V LINE positions o f the A COUPL­
ING switch, —5 volts is removed from the base o f U2232E.
The current now available from R2224 turns on U2232E.
This turns on U2232A and U2232B which allows the sync
separator to operate.
In the AC, LF REJ, HF REJ, and DC positions o f the Ac
COUPLING switch, no signal is applied to the Input Buffer
(Q2212). In the T V FIELD and T V LINE positions of the
A COUPLING switch, the signal selected by the A SOURCE
Switch is supplied to the gate o f Q2212.
Fig. Option 5-1. Block diagram.
Option 5 Page 8 REV. A, OCT 1975