HP 120A - Page 47

Sect. IV Page 7
C235 on horizontal attenuator for flat response.
Switch HOR. SENS, switch to 10 VOLTS/CM and ad 
just C233 for flat response. Now switch back through
the three attenuator ranges and check for 10:1 divi 
sion. Division should be within 1%.
g. Overload
Set HOR. SENS, switch to 1 VOLTS/CM
HOR. SENS. VERNIER to CAL
Apply 50 kc square wave to Horizontal input termi 
nals and also use same signal to trigger Sawtooth
Generator. Adjust output of Sawtooth Generator for
exactly 3cm deflection. Switch HOR. SENS, switch
to 0.1 VOLTS/CM. Observe overshoot and under 
shoot of square wave at midscreen. One-half centi 
meter is maximum permitted deviation from square -
ness. Turn HOR. SENS. VERNIER full counter-clock 
wise. Check for less than 3cm of square wave and for
excessive rounding and overshoot. A maximum of 2%
overshoot is permitted. Return VERNIER to CAL.
h. Phase Adjustment
Set HOR. SENS, switch to 0.1 VOLTS/CM
HOR. SENS. VERNIER to CAL
VERT. SENSITIVITY switch to 100 MILLI 
VOLTS/CM
VERT. SENSITIVITY VERNIER to CAL.
Apply 100 kc sine wave to both Vertical and Horizon 
tal inputs. Adjust amplitude to give about 6cm of de 
flection in each direction. Adjust C107 for closure
of the pattern. Switch both VERT. SENSITIVITY and
HOR. SENS, to 10 VOLTS/CM. Increase input to ob 
tain approximately the same pattern as before. Ad 
just C18 for closure of pattern. Increase the input
frequency until the pattern just opens. This frequency
should be greater than 150 kc. Check phase adjustment
on . 1 V/CM and 1 V/CM ranges also.
4-12 SWEEP GENERATOR
The Vertical and Horizontal amplifiers must be ad 
justed before the Sweep Generator can be adjusted
completely.
a. XI Calibration
Set SWEEP TIME switch to 5 MILLISECONDS/CM
SWEEP EXPAND switch to XI
Apply 100 cps from a Time Marker Generator to Ver 
tical input terminals. Adjust TRIGGER LEVEL con 
trol and choose either INT+ or - for best pattern.
Adjust XI Sweep Gain Adjustment, R107, so that the
markers coincide with every other major division
on the graticule.
b. X 5 Calibration
Set SWEEP EXPAND switch C 5
Apply 1 kc from Time Marker Generator to Vertical
input terminals. Adjust TRIGGER LEVEL control
for best pattern. Adjust X 5 Sweep Gain Adjustment
R108, so that the markers coincide will each major
division on the graticule.
c. Sweep Attenuator Compensation
Set SWEEP TIME switch to 10 MICROSECONDS/
CM, SWEEP EXPAND switch to XI
Set C214 to mid-value. Attach 50:1 probe to an addi 
tional monitor oscilloscope calibrator output anc
compensate probe. Attach this probe to pin 2 of V101A
to view sawtooth at input to Horizontal Amplifier.
Apply 10 kc marker pips from a Marker Generator
to the Vertical input terminals. Adjust C214 to com 
pensate fly-back of sawtooth.
d. XI - X5 Compensation
Set SWEEP EXPAND switch to XI
Connect 50:1 probe to output of Horizontal Amplifier,
pin 1 or 6 of V102. Position start of sweep to center
of screen with HORIZ. POS. control. Adjust C105
for compensation of fly-back of sawtooth. Switch
SWEEP EXPAND switch to X 5 and adjust C106 for
proper compensation. Remove probe.
e. Calibrate 50 millisecond Adjustment Control.
Set SWEEP TIME to 50 MILLISECONDS/CM
Apply 10 cps time markers to Vertical input termi 
nals. Adjust 50 ms Calibrate adjustment, R251 for
marker coincidence with every other major division
on the graticule.
f. Calibrate 0. 5 millisecond Adjustment Control
Set SWEEP SPEED TO . 5 MILLISECONDS/CM
Apply Ike time markers from a Time Marker Gene 
rator to the Vertical input terminals. Adjust C223
for marker coincidence with every other major mar 
ker on the graticule.
g. Calibrate 50 MICROSECONDS/CM Adjustment
Control
Set SWEEP SPEED control to 50 MICROSECONDS
/CM
Apply 10 kc time markers from a Marker Generator
to the Vertical input terminals. Adjust C225 for mar 
ker coincidence with every other major division on
the graticule.
h. Calibrate 5 MICROSECONDS/CM Adjustment
Control
Set SWEEP SPEED switch to 5 MICROSECONDS/
CM
Apply 100 kc from Time Marker Generator to the Ver 
tical input terminals. Adjust C226 for marker coin 
cidence with every other major division on the gra 
ticule.
i. Calibrate SWEEP TIME VERNIER range
Set SWEEP TIME switch to 10 MICROSEC-
ONDS/CM
Apply 10 kc time markers from a Marker Generator