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Section IV Model 185B
Paragraphs 4-80 to 4-83
TRIGGER \ /FIRST SAMPLE
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NO DELAY DELAY
I.Y-8.e
Figure 4-9. Effects of Delay
pdse of about 1.3 kseconds duration is produced, The +lo0 volts through R259 until voltage at junction of
leading edge of this comparator blocking oscillator CR219 and R259 reaches +15 volts. When this occurs
pulse triggers three circuits: CR219 begins conduction, halting the sweep. The
charge on capacitor C240 will remain at +15 volts
a. A pulse, taken at pin 2 of T203, is differentiated
until SCANNING (S203) is set to RESET OR EXTER-
and fed via J1 to the sampler unit where it is used to
trigger sampling gate circuits in vertical plug-inunit. NAL. With ,3203 at RESET OR EXTERNAL, capacitor
C240 discharges through resistor R257.
b. Another pulse, taken at pin 4 of T203, is differ- b. RESET OR EXTERNAL. This position of S203
entiated and fed via J1 to sampler unit where it initi-
has two uses: 1) it is used to reset charging capaci-
ates sampling action in the plug-in. When viewed on tor C240 as explained in RECORD, above, or 2) it
an oscilloscope, this pulse often appears double, but
connects 5201, INPUT EXTERNAL SCAN connector,
the second pulse is actually feeding back from the through S203B, to comparator and horizontal amplifier
vertical plug-in unit.
circuits, so that an external signal may be used to
c. Another output (pin 1) is used in the generation drive these circuits. The external signal should be
between 0 and approximately + 12 volts, (With HORI-
of the staircase voltage (paragraph 4-81).
ZONTAL POSITION approximately centered, 0 volts
puts spot on left-hand edge graticule, +12 volts
4-80. In addition, the trailing edge of the comparator
puts spot on right-hand edge.)
blocking oscillator pulse is used to reset the ramp-
gate extender multivibrator, which in turn resets the
c. MANUAL. Operation is similar to RECORD,
ramp (paragraph 4-52). except grid of V201A is connected to center arm of
R255A, SCAN (MANUAL), so that the operator can
4-81. HORIZONTAL-SCAN CIRCUITS.
manually control scanning.
4-82. The horizontal circuits in Model 185B are used
d. INTERNAL. In INTERNAL, the output of unity
both to deflect beam on the crtand to provide scanning amplifier V201A-Q210 is a staircase voltage which
potential for comparator circuit.
results from the following circuit action (see figures
4-10 and 5-20):
4-83. UNITY GAIN AMPLIFIER. V201A-Q210 con-
stitute a unity gain amplifier. Tube V201A and tran- (1) Prior to start of circuit sequence (end of pre-
sistor Q210 amplify the signal, while CR220 provides ceding staircase), staircase capacitor C236 is
dc coupling between the two elements. R270, the discharged, comparator blocking oscillator
Staircase Balance adjustment, sets the beginning of (Q208-TZ03 which generates sampler trigger)
the horizon.ta1-scan signal at 0 volts. The unity am- has not yet generated the next pulse, and diode
plifier is used on all modes of operation of horizontal CR215 is back-biased.
drive except EXTERNAL. The four types of horizon-
(2) When coincidence occurs, comparator blocking
tal drive selected by ,3203 (SCANNING) follow: oscillator Q208-T203 fires, and the resulting
a. RECORD. In RECORD, S203 disconnects C240 pulse is coupled by transformer T203 to diode
from voltage divider R254, R255, R256, and connects CR215. CR215, forward-biased now, conducts,
it to the grid of V201A. C240 charges slowly toward and capacitor C236 begins to charge.
4-10 01255-1 |
ACEC
