Atec Tektronix-1502 - Manual (Page 37)

TM 9-4935-601-14-3&P
Figure 3-7. Chart Recorder Logic.
Horizontal Correction Network. The Horizontal Correction network compares the output of the digital-to-
analog converter U5147 with the inverted slow ramp signal. U5227 inverts the slow ramp signal. The digital-to-
analog output and inverted slow ramp signal are connected to inverting amplifier U5117, which performs
summation and amplification simultaneously. This signal is fed to the Slow Ramp Generator by way of R5118
and will speed up or slow down the Slow Ramp Generator to synchronize it with the paper speed of the Strip
Chart Recorder.
Chart Recorder Logic. The logic control signal that is received through pin 2 of P53 is shaped into a
narrow impulse (negative going) by U5156B and U5156C. This impulse occurs at the trailing edge of the logic
control signal and latches bi-stable multivibrator U5252A and U5252C. Pin 9 of U5252A goes positive and
turns on Q5266, which pulls the motor control line to ground, causing the paper drive motor to start rotating.
The paper drive motor turns off at count 65 by U5252B. A second signal is capable of turning the motor off.
This occurs when the end of the paper is reached and the output from the pulse shaper is stopped. This causes
C5249 to discharge and unlatch the multivibrator.
The multivibrator is initally latched when the inverted control signal from pin 4 of U5156B charges C5249.
The impulse from pulse shaper U5166A and U5166D keeps C5249 charged. The multivibrator latch (output of
pin 10) disables the reset of the counter and turns Q5144 on. This locks out the logic control input line.
Stylus heat control comes from Q5239, which is turned on by flip-flop U5127A. This flip-flop is energized
by PEN LIFT signal from the Vertical board. The RETRACE signal turns the stylus heat off. This signal brings
the flip-flop back to its original state (where pin 1 is low). The "Q" output also controls the chart pen motor
power switch as well as providing the "J" input to flip-flop U5127B.
U5127 controls the start of the Slow Ramp Generator and controls the horizontal correction signal disable
network (Q5112). The Slow Ramp Generator starts when Q2 of the Counter goes high. The output "Q" of
U5127A resets U5127B to allow the Slow Ramp Generator to return to its original mode. The horizontal
correction disable network Q5112 is controlled by the signal from pin 14 of U5127B, through Q5114.
REV A FEB 1980
3-12