Tektronix 465 User Manual

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Circuit Description-465
Third Cascode Amplifier
The trigger pickoff circuit only provides a signal to one
emitter follower. This emitter follower (Q262) in turn
provides the trigger signal to the Trigger Generator circuits
in the CH 2 positions of the SOURCE switches.
VERTICAL SWITCHING CIRCUIT
General
The Vertical Switching Circuit determines whether the
Channel 1 or Channel 2 or both signals are connected to the
Vertical Output Amplifier Circuit. In the alternate and
chopped modes of operation both channels are alternately
displayed on a shared time basis. Fig. 3-4 shows a detailed
block diagram of the Vertical Switching Circuit. A
schematic of th is circuit is shown on diagram 3 at the rear
of this manual.
Diode Gates
The Diode Gates, consisting of four diodes each, can be
thought of as switches which allow either of the Vertical
Channel 1
From { CH 1
Preamp ! POSITION !
CH 1 Diode
Gate
CR304
CR305
CR307
CR308
Preamp output signals to be coupled to the Vertical Output
Amplifier. CR304, CR305, CR307 and CR308 control the ~,·
Channel 1 output and CR314, CR315, CR317 and CR318 •:
control the Channel 2 output. These diodes are in turn
controlled by the Switching Multivibrator for dual trace
displays, or by the VERT MODE switch for single trace
displays.
Channel 1 Only Display. When the CH 1 pushbutton is
pressed, -8 volts is applied to the junction of
CR315-CR317 in the Channel 2 Diode Gate through R367
(see simplified diagram in Fig. 3-5). This forward biases
CR315 and CR317 and reverse biases CR314 and CR318.
CR314 and CR318 block the Channel 2 signal so it cannot
pass to the Delay Line Driver stage. At the same time in the
Channel 1 Diode Gate, CR305 and CR307 are connected to
+5 volts through R371. CR305 and CR307 are held
reverse-biased while CR304 and CR308 are forward biased.
Therefore, the Channel 1 signal passes to the Delay Line
Driver stage.
Channel 2 Display Only. When the CH 2 pushbutton is
pressed, the above conditions are reversed. The junction of
CR305-CR307 is connected to -8 volts through R376 and
R348
S338B
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Norm Trigger
Signal To
Trigger
Generators
C
CH 2 Diode
""'-----+----., Gate
f
4
] ATrigger
3-6
-·· .... _ .... ·.·
:· .·• ·:-. ;-
Alt. Trace
Sync Pulse
Switching
Multi
0364
0374
CR314
CR315
CR317
CR318
Signal From
A Trigger View
.._ ___ .....,.,. Amp
Chopped
>-----. :~a;~:1.
Amplifier
Fig. 3-4. Detailed block diagram of the Vertical Switching Circuit.
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Tektronix 465 Specifications

General

Brand	Tektronix
Model	465
Category	Test Equipment
Language	English