HP 120A - Bandwidth; Common-Mode Rejection; Horizontal Amplifier

Sect. IA Page 3
age constant as read on the ’ ’ reference VTVM ” . Ob 
serve the frequency where the vertical deflection has
decreased to 7. 07 cm. Re-position pattern, if neces 
sary. This frequency is the bandwidth of the vertical
amplifier and should be greater than 200 kc.
1A-4 COMMON-MODE REJECTION
1) Remove the jumper from the lower vertical input
terminal to ground and connect a lead from the lower
red terminal to the upper red terminal.
2) Set the VERT. SENSITIVITY switch to 10 MILLI 
VOLTS/CM and the VERNIER to CAL.
3) Connect the ’ ’ reference oscillator ” between the
two terminals and ground. Monitor this input with
the ’ ’ reference VTVM ” .
4) Set the frequency of the ’ ’ reference oscillator ” to
Ike and adjust its output to read 0. 35 volts rms on
the "reference VTVM ” .
5) The vertical deflection on the 120A should be 1cm
or less.
6) Replace the jumper removed in step 1.
1A-5 HORIZONTAL AMPLIFIER
First check balance as described in paragraph 4-lla.
Next, check horizontal sensitivity by connecting a
Ike signal from the "reference oscillator ” to a cali-
brated vertical amplifier. Set the VERT. SENSITIVI 
TY switch to . 1 VOLTS/CM and the VERNIER to CAL.
Set the output of the "reference oscillator" to give a
vertical deflection of exactly 10 cm. Now feed the
same signal into the horizontal input terminals. Set
the HOR. SENS, switch to . 1 VOLTS/CM and the
VERNIER to CAL. Without changing the output of the
"reference oscillator ” the horizontal deflection should
be from 9. 5 to 10. 5 cm. Repeat this procedure on the
1 and 10 VOLTS/CM ranges. If the sensitivity is not
within specification, see paragraph 4 -lib.
a. Sensitivity -
Conduct test exactly as for corresponding sensi 
tivity steps of vertical amplifier.
b. Bandwidth -
Conduct test exactly as for vertical amplifier
except use 0.1 VOLTS/CM sensitivity.
c. Phase Comparison -
1) Set HOR. SENS, switch to 0.1 VOLTS/CM and
VERNIER to CAL. Set VERT. SENSITIVITY switch to
100 MTT JJVOLTS/ CM and VERNIER to CAL.
2) Connect a lead from the horizontal input terminal
to the vertical input terminal.
3) Connect the "reference oscillator" to the parallel 
ed input terminals.
4) Set the frequency of the "reference oscillator" at
Ike and adjust its output to give 8 cm of deflection
on either axis. Use VERT, and HORIZ. POS. con 
trols as necessary. The presentation should be a
straight line at about 45° inclination from either axis.
5) Increase the frequency of the "reference oscil 
lator" and adjust its output to keep 8 cm of deflection.
6) Observe the frequency where the straight line
opens to an ellipse with a minor axis separation of
0. 2 cm. This frequency should be 100 kc or more.
1A-6 SWEEP GENERATOR
a. Triggering -
1) Set VERT. SENSITIVITY switch to 10 VOLTS/
CM. Apply a 10 kc sine wave from the "reference
oscillator" to the vertical input terminals and also
to the horizontal input terminals. Make sure the
TRIGGER LEVEL control is in the AUTO position.
2) Set the SYNC switch to INT+ and adjust the out 
put of the "reference oscillator" to give about 6 cm
of vertical deflection. Adjust SWEEP TIME switch
to give several cycles displayed across the screen
of the cathode-ray tube. The pattern should be stable
with the signal "positive going" (upwards from the
starting point).
3) Switch SYNC switch to INT-. Pattern should be
"negative going" (downwards) from the starting point.
4) Switch SYNC switch to EXT. Pattern should be
"negative going" (downwards) from the starting point.
5) Reduce output of "reference oscillator" until pat 
tern looses synchronization. The pattern should be
less than 0. 25 cm in height.
6) Switch SYNC switch to INT- and repeat step 5.
The pattern should be less than 0. 5 cm in height.
7) Switch SYNC switch to INT+ and repeat step 5.
The pattern should be less than 0. 5 cm in height.
b. Sweep Calibration -
1) Connect the output of the "time interval generator"
to the vertical input terminals.