Tektronix 1710J Series Instruction Manual page 90

Theory of Operation
Sweep Generators and Horiz Output, Diagram 4
Sweep Generator
5–12
U552B (line rate sweep generator) and U552A (field rate sweep generator) are
integrators, one of which is disabled while the other is running. The selection is
controlled by the H and V trigger signals from the sync generators (Diagram 3)
and the LIN/FLD control line from the microcontroller. When a trigger arrives,
for the selected sweep, the D-type flip-flop (U541A or B) clear is high and preset
is low, to set Q high and turn on Q451 or Q450, which discharges the integrating
capacitor (C448 or C453). See Figure 5–4. The Q output of U541A or B going
high also starts a one-shot (U741A or B) which pulls the flip-flop preset low
which assures at least 2 s (line-sweep one-shot time constant) of discharge
(retrace) time. Field sweep one-shot time constant is 2 ms. At the end of the time
constant preset goes high and clear goes low causing the flip-flop Q output to go
low and turn off Q451 or Q450 to start charging the integrating capacitor.
Current source for the integrators is through R654. When a one line or field
sweep (including RGB parade) is selected, pin 3 of U735A is pulled low and
effectively shorts out R654 to provide more current for a faster sweep. Q750
provides a compensation for 50 Hz sweep by taking away a small amount of
current when operating with 625/50 Hz sweep rates.
U541 pin 3
H TRIGGER
U541 pin 5 (Q)
1-line sweep
with sync
U541 pin 5 (Q)
2-line sweep
with sync
U552 pin 6
1-line sweep
U552 pin 6
2-line sweep
U741 pin 6
Figure 5–4: Timing signals for 1-line and 2-line sweep
1710J-Series Waveform Monitors