TM 9-6625-1753-14
C2
signals to the delayed sweep gate multivibrator, thereby inactivating the delayed sweep.
d. The arming signal from the delayed pick-off circuit is coupled from transformer T8601, through diode CR8104, to the
base of transistor Q8104. The bistable armed multivibrator changes states: Q8104 is at cutoff and Q8103 is conducting. The
leading edge of the negative gate at the collector of Q8107 is differentiated by C8118 and R8143 and applied to the base of
transistor Q8103 through diode CR8103. This disarming trigger reverts the armed multivibrator to its initial condition. After
the bistable delayed sweep gate multivibrator has been triggered, it will revert to its original state as determined by the setting
of SWP LENGTH adjustment R8159. The delayed sweep will remain inactivated until the armed multivibrator is rearmed by a
signal from the delayed pick-off circuit.
e. The development of the strobe and unblanking pulses are identical to that described for the triggered-delayed mode.
Automatic provision is made for turning off the NDT sweep when the DA sweep has terminated. This prevents brightening of
the sweep retrace in the strobe position.
3-22.
Delayed-Armed Mode (Figs. 3-22, 3-23, and 6-4)
When the DISPLAY LOGIC switch is set to ARM DLY'D, the delayed sweep is applied to horizontal deflection plates. The
delayed-armed sweep circuit is similar in operation to the armed-strobe mode described earlier, except that the strobe circuit
is not inactivated.
3-23.
Horizontal Deflection Circuit (Figs. 3-24 and 6-4)
a. When the DISPLAY LOGIC switch is set to X AMP, the EXT TRIG input connector of the delayed sweep becomes the
X amplifier input. Simultaneously, the delayed sweep LEVEL control becomes the variable X AMPlifier ATTENuator control.
The PULL EXT/10 setting provides 10:1 attenuation of the X input signal. Thus external signals may be applied to the X AMP
front-panel BNC connector. These signals are coupled to X input amplifier V8101 and V8102. The output of this amplifier is
coupled to the horizontal deflection circuit via the X AMP setting of the DISPLAY LOGIC switch (fig. 3-13). The output from
V8102 is applied through a voltage divider network to the base of emitter follower Q8301 via the DISPLAY LOGIC switch.
Figure 3-19. Simplified timing diagram, delayed-triggered display.
possible for the next appropriate triggering signal to initiate the delayed sweep. In this mode of operation, the delayed sweep
does not start precisely at the delay time indicated by the DELAY VERNIER and NDT TIME/DIV control settings, but instead
is initiated by the next suitable triggering following the indicated delay interval. This mode from now on will be referred to as
the delayed-armed mode of sweep operation. The armed lockout diode, CR8102, is not forward-biased by the voltage applied
to it from the collector of Q8103, thus opening the triggering circuit to delayed sweep gate generator Q8106 and Q8107.
b. The SWP READY lamp on the front panel goes on when the delay time has elapsed and indicates that the delayed
sweep circuit is ready to be triggered. When the delayed sweep is triggered, the SWP READY lamp then goes out. If the
delayed-armed sweep is triggered immediately at the completion of the delay time, the SWP READY lamp may not appear to
go on.
c. The next suitable trigger from the DA trigger is applied to the delayed sweep multivibrator, which immediately changes
states (it flips). Q8106 forms a positive gate while Q8107 forms a negative gate during the "delayed" sweep forward interval.
In the quiescent state of the armed multivibrator, Q8103 is at cutoff and Q8104 is conducting. The armed lockout diode,
CR8102, is back-biased by the voltage applied to it from the collector of Q8103. This action locks out incoming triggering
Figure 3-20. Armed strobe mode, functional block diagram.
3-19
