Tektronix 507, Инструкция по эксплуатации

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beam current is completely cut off. As soon as
a trigger pulse appears and a sweep starts, a
positive pulse of approximately 100 volts is re­
quired at the grid of the cathode-ray tube to
turn the beam on. This pulse must have a very
fast risetime and a very flat top to insure fast
unblanking and uniform image brightness. Both
conditions are accomplished by the unblanking
amplifier V144-V154 and the associated cathode
follower V I53.
The negative pulse at the plate of the minus
multivibrator V I05 is coupled to the grids of the
unblanking amplifier via a frequency-compen­
sated voltage divider. The shunt-compensated
plate-load impedance of the amplifier circuit
produces a positive pulse having a very fast
risetime. The cathode-follower circuit V I53 pro­
vides a high-impedance, low-capacitance load
to the amplifier, at the same time providing a
low-impedance driving source for the grid of the
cathode-ray tube. The cathode-follower V I43
provides a low-impedance source of screen
voltage for the amplifier tubes. The UNBLANK­
ING ADJ. R146 provides a means of adjusting
the screen voltage to obtain the desired 100-volt
unblanking pulse.
Trip Pulse
A thyratron pulse generator produces a man­
ually-initiated pulse at a rear-panel connector
for triggering a trip-pulse generator. In the
quiescent state the divider R52-R53 holds the grid
of the thyratron below cutoff. When the MAN­
UAL TRIP PULSE switch is depressed C50 charges
and the positive pulse developed at the grid fires
the thyratron. Since the thyratron is connected
as a cathode follower, the cathode pulls up
sharply to develop the output pulse of approxi­
mately 700 volts. In producing the output pulse,
however, the cathode voltage approaches suf­
ficiently close to the voltage at the plate to
extinguish the thyratron and return the circuit to
its quiescent state.
VERTICAL DEFLECTION SYSTEM
Since the Type 507 does not contain a vert­
ical amplifier, the vertical defection circuit con­
sists mainly of an attenuator and a positioning
network.
The input signal is developed across the 72-ohm
attenuator resistance. The desired percentage of
the input signal is selected from a tap on the div­
ider by means of the ATTENUATOR switch, from
where the signal is coupled to one of the ver­
tical-deflection plates in the cathode-ray tube.
The other vertical deflection plate is connected
to ground to accommodate the single-ended
input signal.
When the SIGNAL MODE switch is in the EX­
TERNAL NORMAL position, positive-going por­
tions of the input signal produce upward deflec­
tion in the cathode-ray tube; in the EXTERNAL
REVERSED position, positive-going signals pro­
duce downward deflection. In the INTERNAL
MARKER position of the switch, time markers
from the Time-Mark Generator are coupled to
the lower deflection plate and the upper plate is
connected to ground.
Either of two positioning circuits may be con­
nected into the vertical deflection circuit. When
fin
the toggle switch SW435 is in the 50 VOLT
STEPS position, a tapped divider connected be­
tween +150 volts and —150 volts is connected
into the circuit. By means of the POSITIONING
switch, the positioning voltage may be selected
in 50-volt steps between these two limits. Test
points and adjustments are provided to accur­
ately set the upper and lower voltage for the
divider.
When SW435 is in the VARIABLE position,
a continuously variable positioning control is
connected into the circuit. The VARIABLE posi­
tioning control is part of a divider connected
between +225 volts and —250 volts. The resis­
tance values in the divider are such that the
range of positioning voltage is about 325 volts,
a bit greater than the 300-volt range provided
by the 50 VOLT STEPS control. Front-panel EX­
TERNAL VOLTMETER connections are provided to
monitor the VARIABLE positioning voltage. The
VARIABLE DEFLECTION SENSITIVITY MONITOR
switch may be used to reverse the voltmeter
connections, or to disconnect the VARIABLE
position control from the front-panel voltmeter
connections if desired.
®
CIRCUIT DESCRIPTION — TYPE 5 0 7
2-3