Tektronix 543B Instruction Manual page 16

cathode followers are returned to ground through vertical
DC BAL control R495, which is adjusted to equalize the
dc voltage (about --68.5 volts) on the bases of delay-line
driver transistors Q514 and Q524. The DC SHIFT control
(R502) varies operating voltage and compensates for errors
of thermal balance in Q514 and Q524 as well as Q584
and Q594.
The balanced delay-line driver stage is a push-pull cas-
code amplifier with an adjustable vertical gain control (R520)
connected in the emitter circuit of the two transistors. Gain
is adjusted by controlling the amount of degeneration in the
emitter circuit of the transistors.
operation points of Q513 and Q523 which provide the
reverse termination for the delay line.
The RC networks in the collectors of Q514, Q524, G584,
and Q594 set the individual transistor operating points for
thermal balance.
Vertical Output Amplifier. The vertical output amplifier
must properly terminate the 186D delay line and provide
broadband amplification of the vertical signals. The delay
line is properly terminated by adjusting C568, L554, and
1560.
The output amplifier is a wideband amplifier stage con­
sisting of Q584, Q594, V584 and V594 and associated ele­
ments. High-frequency compensation in this stage is pro­
vided by peaking coils L588, L589, L598 and L599 in the
plate circuits of V584 and V594. The high-frequency re­
sponse is varied by adjusting C581 and R580, which pro­
vide variable high-frequency degeneration in the emitter
circuit of Q584 and Q594.
The output stage of the vertical amplifier is a hybrid
push-pull cascode amplifier.
used to match the low impedance of the transistorized verti­
cal-amplifier system to the higher impedance required at the
erf vertical deflection plates.
Trigger-Pickoff Circuit. The irigger-pickoff transistor ampli­
fier Q543, noi only provides trigger signals to the time
base, but supplies the VERT SIG OUT jack with a vertical
signal.
Beam-Position Indicators.
B538 and B539 driven by Q534 and located on the front
pane! above the ert, indicate the relative vertical position of
the trace with respect to the center of the graticule. When
the beam is centered vertically, the potential across either
neon is insufficient to light it. The current through Q534,
and thus the voltage across the neons, will change as the
beam is positioned up or down on the crt. The voltage
across one neon will increase, causing it to light, and the
voltage across the other neon will decrease, causing it to
remain extinguished. The neon that lights will indicate the
direction in which the beam has been moved.
Time Base
The Time Base consists of the sweep trigger and the
sweep generator circuits. The sweep trigger circuit includes
controls for selecting the type, source, and level of the
trigger to be used, and circuit elements for regenerating the
selected trigger into a pulse suitable for triggering the
sweep generator. The sweep generator circuit is basically
0
R532 and R533 set the
This circuit configuration is
The beam-position indicators
Circuit Description — Type 543B/RM543B
a Miller runup circuit. The sweep generator provides ramp
voltages for the horizontal deflecion system and the SAW­
TOOTH OUT connector, unblanking pulses, and +
pulses.
Trigger Generator. The input to the sweep trigger circuit
is selected by TRIGGER SLOPE switch SW10A from the
trigger-pickoff circuit in the vertical amplifier, the power
transformer for line triggering, or from rhe front-panel TRIG­
GER INPUT connector. TRIGGER MODE switch SW10B
permits further selection of the type of triggering signal;
either automatic, ac low-frequency reject, ac or dc. Once
the type and source of triggering signal has been selected,
the slope on which triggering is desired is selected by TRIG­
GER SLOPE switch SW10A.
signal required by the sweep trigger circuit is selected by
adjusting TRIGGERING LEVEL control R17. After this trig­
gering signal has been selected by the preceding controls
and switches, it is applied to trigger input amplifier V24.
The trigger-input amplifier provides a source of positive­
going signal to drive the following stage and, by means of
the TRIGGERING LEVEL control, enables the operator to
select the point on the signal at which triggered operation
will occur.
To trigger from a positive-going signal, the grid of the
V24A section is connected to the inpur signal source. The
grid of the V24B section is connected to a dc bias source,
which is adjustable with the TRIGGERING LEVEL control.
This bias voltage esfablishees the voltage present at the
plate under no-signal conditions.
The voltcge at the grid of V24A and the voltage at the
plate of V24B are in phase with each other: that is, they
both go through ac zero in the same direction at rhe same
time. Thus, the V24A section acts as a cathode-follower,
and the signal voltage developed across the cathode resis­
tors becomes the input signal to rhe V24B section.
To trigger from a negative-going signal, the grid of the
V24A section is connected to the TRIGGERING LEVEL con­
trol, and the grid of V24B is connected to the input signal.
With this configuration, the voltage at the plate of the V24B
section will be 180° out of phase with the input-signal
voltage.
In each of the cases outlined previously, a positive-going
signal is produced at the plate of the V24B section of the
Trigger-Input Amplifier irrespective of the polarity of the
input signal.
D29 and D30 are limiters and allow the trigger circuit to
count down to provide triggers at a slow enough rate for
the sweep gating multivibrator to react.
voltage level on the base of Q35 is set by the collector
of Q34 whose base voltage is set by R39 (TRIG LEVEL
CENTERING). The amplitude of the triggering signal neces­
sary to cause operation of the trigger multivibrator is de­
termined by the setting of the TRIGGERING LEVEL control.
Trigger amplifier Q34 provides additional amplification
to the trigger signal before applying the signal to the base
of Q35.
In the quiescent state, ready to receive a signal, Q35
of the trigger multivibrator is conducting and the collector
voltage is down. Since the collector is dc-coupled to the
base of the Q45, that base is held below cutoff. With Q45
gate
The level of the triggering
The quiescent
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