TM 11-6625-3025-14/ET426-AA-MMA-010/E154 VII210/T.O. ,3A1-8-902-1-1
The V bar card controls development of vertical elements in the test patterns. This card contains a voltage
controlled astable multivibrator Q1 and Q4 which runs freely during the active line time. The repetition rate is established
by current control transistor Q3. During the horizontal and vertical blanking intervals, the astable multivibrator is clamped t o
a control voltage which establishes the position (phase) of the pattern in the horizontal dimension of the raster. The clamp
circuit incorporates a field effect transistor (Q5) operating in the enhancement mode to connect the control level to the
base of Q4 during the blanking interval. The control level determines the time required for Q4 to initiate cycling after
blanking, effectively positioning the pattern on the tv line. The level is introduced through pin U to emitter-follower Q16,
which includes zener diode CR8 to produce a drop in the 0 to 5v input voltage. Thus the voltage at R40 remains negative
throughout the range of control.
Proper operation of the clamp transistor Q5 requires a control pulse which swings from +5v to -5v. The clamp
pulse at pin T is then routed to saturating stage Q15. The signal at the collector of Q15 is biased by R5 and R6 to turn on
Q14. This pulse, swinging from near 0 to -5v is used to control Q13 whose emitter is referenced to -5v. The pulse at the
collector of Q13 swings from +5v to -5v, and is used to control Q5.
Each cycle of the astable develops a trigger from monostable multivibrator Q7 and Q8 which develops the precise
sharp pulse required to produce a fine line or dot at all scanning rates. Monostable outputs and H bar pattern elements
from the H bar card are combined on the V bar card logic circuits to form the pattern selected. If V bars are to be formed,
the monostable Q7 and Q8 operates for each tv line. No voltage is applied to pin L of the V bar card or to pin W of the H
bar card, so H bar elements do no appear. To produce the bar pattern, voltage is applied to pin L of the V bar card.
Monostable Q7 and Q8 operates as V bars, but H bars are applied through CR7 to Q11, which turns on and locks the
monostable to produce the H bar element.
To produce dots, the monostable Q7 and Q8 is allowed to operate only on selected lines. The H bar element is
developed at Q3, as voltage is applied to pin W on the digital H bar card. This pulse is routed through bias resistors R26
and R27 to Q10, which clamps the monostable in the opposite phase and prohibiting pattern output. When dots are to be
produced, the clamp is released for those horizontal lines.
To produce H bars only, both clamp transistors are used, locking the monostable in one phase and then the other,
preventing development of any V bar elements.
4-9.
Resolution and Multiburst. Development of the various resolution patterns involves the interrelated action of the
resolution (figure FO-14), multiburst (figure FO-15) and multiburst clock (FO-16) cards.
4-15
