HP 120A - Horizontal Amplifier

Sect. IV Page 6
SYNC switch to INT
TRIGGER LEVEL control to AUTO.
SWEEP TIME control to 200 MICROSECONDS/
CM
Apply 5 kc square wave to vertical input terminals
Adjust for 8cm deflection. Adjust C6 on vertical at 
tenuator for a flat top square wave Switch VERT.
SENSITIVITY control to 1 VOLT/CM and increase
input to give 8cm deflection. Adjust C2 for flat res 
ponse. Switch Vertical Sensitivity to 10 V/CM and
check for flat response. Should be within 1%. Now
switch back through the four attenuator positions and
check for 10:1 steps. All should be 10:1 within 1%.
h. Overload
Set Vertical AC-DC switch to AC
VERT. SENSITIVITY switch to 1 VOLTS/CM
VERT. SENSITIVITY VERNIER to CAL
SYNC switch to INT+
TRIGGER LEVEL control to AUTO.
SWEEP TIME switch to 10 MICROSECONDS /
CM
Apply 50 kc square wave to vertical input terminals.
Adjust for exactly 3cm deflection. Switch VERT.
SENSITIVITY control to 100 MILLIVOLTS/CM. Check
range of VERT. POS. control by positioning each
peak of square wave beyond center screen. Observe
overshoot or undershoot of square wave at midscreen.
One-half centimeter is maximum permitted deviation
from squareness. Turn VERT. SENSITIVITY VER 
NIER full counter-clockwise. Check for less than 3cm
of square wave and for excessive rounding or over 
shoot. Return VERNIER to CAL. Reduce input to give
exactly 3cm of deflection. Switch VERT. SENSITIVI 
TY control to 10 MILLIVOLTS/CM. Check for over 
load as before.
i. Frequency Response
Set VERT. SENSITIVITY switch to 10 MILLI 
VOLTS/CM
VERT. SENSITIVITY VERNIER to CAL
Apply 2 kc sine wave to vertical input terminals and
also measure this input with a ($400D. Adjust input
signal for exactly 10cm deflection. Note reading on
400D. Apply 200 kc sine wave and adjust the input to
the same reading on 400D. Deflection on screen
should be greater than 8cm.
4-11 HORIZONTAL AMPLIFIER
a. Balance
Set HOR. SENS, switch to 10 VOLTS/CM
HOR. SENS. VERNIER to CAL
VERT. SENSITIVITY to OFF
Position spot to center of screen with HORIZ. POS.
control. Turn HOR. SENS. VERNIER full counter 
clockwise position and reposition with Horizontal Bal 
ance Adjustment, R110. Turn HOR. SENSITIVITY
VERNIER to CAL and center spot with HORIZ. POS.
control. Repeat until there is no movement of spot
when VERNIER is rotated. Set HORIZ. POS. control
to center. The spot should now be on the screen.
b. Set Gain
Set HOR. SENS, control to 0.1 VOLTS/CM
HOR. SENS. VERNIER control to CAL
Apply 1. Ov peak-to-peak from a Voltmeter Calibra 
tion Generator to the Horizontal input terminals. Set
Horiz. Gain Adjustment, R114, for exactly 10cm of
deflection. Check this setting at high and low line
voltages.
c. DC shift, Hum, and Microphonics.
Set Horizontal AC-DC switch to DC
HOR. SENS, switch to 0.1 VOLTS/CM
HOR. SENS. VERNIER to CAL
Short input. Switch Horizontal AC-DC switch from
DC to AC. Spot should not shift more than 0. 05cm.
There should be no distortion of the spot due to hum
or ripple. Remove short and apply open shielded 3/4 ”
plug. Check again for spot distortion. When jarring
120A with input shorted there should be no horizontal
instability.
d. Compression
Set HOR. SENSITIVITY switch to 0.1 VOLTS/CM
HOR. SENSITIVITY VERNIER to CAL.
Connect insulated (§>)400D across horizontal deflection
plate terminals. DANGER, HIGH VOLTAGE I Switch
to 1 volt range on 400D. Apply Ike sine wave to Hori 
zontal input terminals and adjust for a reading of 0.95
volts on the 400D when the spot is positioned to the
center of the screen. Position the spot to the right 
hand edge line of the graticule and read the 400D. Po 
sition the spot to the lef-hand edge line of the grati 
cule and read the 400D. The difference of each read 
ing from the reference 0. 95 is the compression in
percent. A maximum of 6% is permitted.
e. Square Wave Response
Set HOR. SENSITIVITY switch to 0.1 VOLTS/CM
HOR. SENSITIVITY VERNIER to CAL
Connect Sawtooth generator to Verticil input termi 
nals. Apply 50 kc square wave to Horizontal input
terminals and also use same signal to trigger Saw 
tooth Generator. Adjust C107 for minimum capacity.
Adjust C110 for optimum square wave. A maximum of
2% overshoot is permitted.
f. Attenuator Compensation
Set HOR. SENSITIVITY switch to 1 VOLTS/CM
HOR. SENSITIVITY VERNIER to CAL
Apply 5 kc square wave to Horizontal input terminals
and also use same signal to trigger a Sawtooth Gene 
rator connected to Vertical input terminals. Adjust