Horizontal - Tektronix 2235A Instruction Manual

Theory of Operation
-
2235A
Instruction
When the A Sweep is displayed, the collector of Q682 is
LO and that of Q683 is HI. CR687 is turned on, reverse
biasing CR817, preventing Z-axis drive current from
flowing through the diode. With CR684 reverse biased,
additional Z-axis drive current to intensify the A Sweep
will be supplied whenever CR685 is biased off. Since
input pin 5 of U665B is HI, the gate output and therefore
the conductive state of CR685 is determined by the
B-GATE(L) signal through U660C. Whenever the B
Sweep is running, the output of U665D will be LO. This
will cause the output of U665B to also be LO and CR685
will be biased off. If the B Sweep is not runnirlg, the out-
put of U665B will be HI and CR685 will be biased on. This
will bias off CR816 and the A Sweep will not be
intensified.
If U670B is set to display the B Sweep (Q HI and
a
LO),
CR684 will be biased on, reverse biasing CR816 to
prevent Z-axis drive through that diode. With CR687 off,
the B Sweep will be displayed if CR680 is also reverse
biased. Whenever the B Sweep is running, the output of
U665D will be LO. Diode CR680 will then be reverse
biased and Z-Axis drive current will flow through CR817.
If the B Sweep is not running, the output of U665D is HI,
forward biasing CR680 and therefore reverse biasing
CR817. No Z-Axis drive current can then flow through
CR817.
HORIZONTAL
The Horizontal Amplifier circuit, shown on Diagram 8,
provides the output signals that drive the horizontal crt
deflection plates. Signals applied to the Horizontal
Preamplifier can come from either the A or the B Miller
Sweep Generator (for sweep deflection) or from the XY
Amplifier (when X-Y display mode is selected). Sweep
switching is under control of the Alternate Display
Switching Logic circuit. See Figure 3-4 for the block
diagram of the Horizontal Amplifier.
The Horizontal POSITION control, XI0 Magnifier
circuitry, and the horizontal portion of the Beam Find
circuitry are also contained in the Horizontal Amplifier
circuit.
Horizontal Preamplifier
The Horizontal Preamplifier selects display modes and
amplifies input signals for application to the Horizontal
Output Amplifier.
Figure 3-4. Block diagram of the Horizontal Amplifier.
-
Scans by
ARTEK MEDL4
3
FROM A SWEEP A SWEEP
QENERATOR
4
B SWEEP
FROM B SWEEP
GENERATOR
A DlSP
FROM ALTERNATE
DISPLAY
SWITCHING LOQlC
B DlSP
SWEEP
SWITCHING
0730,0732,
0740,0742.
0745
FROM
Z-AXIS
AMPL
BEAM
FIND
T
1
HORIZ OUTPUT
AMPL
0768,0770.
0775,0778,
0779,0780,
0785,0789
X-AXIS SIQNAL
FROM A TRIGGER
TO CRT
HORlZ
- - - - )
DEFLECTION
PLATES
FROM A SEClDlV m ( L )
SWITCH
A
X-AXIS
AMPL
U715A
m
ENABLE
0737
7883-26
- - - )
HORlZ
PREAMP
U780
- +