TM 9-6625-1753-14
C2
Figure 3-14. Normal sweep mode, functional block diagram.
(2) The grid of the Miller integrator moves negatively when the clamp is unlocked. The plate voltage of V8203 rises
positively, carrying the saw cathode-follower (V8204) grid, cathode, and timing capacitor in the same direction. A flow of
current is required into the charging capacitor if the voltage across this capacitor is to change. The charging current must flow
through the charging resistor. The time required to change the voltage across the charging capacitor determines the sweep
time.
(3) The positive voltage swing on the opposite side of the timing capacitor tends to prevent the grid side from
swinging negatively. It also increases the voltage to which the timing capacitor is trying to charge. The net result is to
straighten out the charging curve (sweep voltage) by maintaining a constant current flow in the capacitor. Since the grid of
V8203 remains at a constant potential within a small fraction of a volt, the current through the charging resistor remains
constant, and the sweep timing capacitor thus charges at a constant rate. The resulting linear sawtooth waveform is applied
to the horizontal deflection system.
c. Sweep Length.
(1) The sweep length, or the total duration of the sweep for any given sweep rate, is determined by the setting of
sweep LENGTH adjustment R8263. A portion of the positive sawtooth voltage is fed back to turnoff emitter follower Q8208,
and saw turn-off diode CR8204.
(2) If sweep LENGTH R8263 is correctly set, diode CR8204 will conduct when the positive-going excursion of the
sawtooth has traveled 10.5 to 11 divisions on the screen. This positive peak signal will then be conducted through diode
CR8204 to the base of Q8206. Upon receiving this positive pulse, the sweep gate multivibrator will revert rapidly to its original
state with Q8206 conducting, and Q8207 at cutoff. The positive step from the collector of Q8206 returns disconnect diodes
CR8216, CR8209, CR8211, and CR8205 to their conducting state, thus discharging the timing capacitors. The Miller circuit
now returns to its quiescent level and is ready for the next sweep cycle after the lockout time interval is completed.
Figure 3-15. Timing diagram for normal sweep display.
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