HP 120A - Page 48

Sect. IV Page 8
to the Vertical input terminals. Check for at least 3
markers displayed within 10cm when the SWEEP
TIME VERNIER is turned full counter-clockwise. Re 
turn VERNIER to CAL.
j. Sweep Length
Set SWEEP TIME control to 200 MIC ROSE C-
ONDS/CM
Apply 1 megacycle time markers from a Time Marker
Generator to the Vertical input terminal. Adjust
TRIGGER LEVEL control for stable pattern, if nec 
essary. Adjust Sweep Length Adjustment, R225, foi
10. 5cm of sweep. Check at high and low line voltages.
k. Linearity
Set SWEEP EXPAND switch to XI
SWEEP TIME switch to 5, 10, 100, 200 MICROSEC-
ONDS/CM; 1, 10, 20, 50, 100, 200 MILLISECONDS
/CM and with the SWEEP EXPAND switch in the X 5
position 5 and 200 MICROSECONDS/CM; and 5 MIL 
LISECONDS/CM.
Choose the appropriate marker rate and check the
sweep linearity on the ranges listed for XI and for
X5. A maximum non-linearity of 3% is permitted.
1. Hum
Set SWEEP TIME switch to 1 MILLISECOND/CM
SYNC to INT
TRIGGER LEVEL control to AUTO.
SWEEP EXPAND switch to XI
Apply Ike sine wave to the Vertical input terminals.
Turn the SWEEP TIME VERNIER down approximate 
ly 3:1 and tune to observe hum modulation on sweep.
Switch SWEEP EXPAND switch to X5. Adjust Hum
Balance control, R360, for minimum hum. In ad 
dition, there should be less than . 05cm shiftiin the
trace.
m. Starting Point Variation
Set SWEEP TIME switch to 5 MICROSEC -
ONDS/CM
SYNC switch to INT
TRIGGER LEVEL control to the AUTO position
SWEEP EXPAND switch to XI
While triggering from Ike source, switch SWEEP
TIME switch one position at a time down to 10 MIL 
LISECONDS/CM and look for horizontal movement
of the starting point. A maximum of 0. 25cm is per 
mitted. Look for evidence of rounding or overshoot
of gate waveform.
n. Hold-Off
Set SYNC switch to INT
TRIGGER LEVEL to AUTO.
SWEEP EXPAND switch to XL
Apply 500 kc triggers from a oscillator to the Ver 
tical input terminals. Set the input line voltage to
102 volts. Switch the SWEEP TIME switch through
its ranges and look for any pulling of the starting
point of the sweep. No pull-in is permitted. Return
the line voltage to 115 volts.
o. Unblanking
Set SWEEP TIME switch to 5 MILLISECONDS/CM
SYNC switch to EXT
TRIGGER LEVEL control to AUTO
VERT. SENSITIVITY switch to OFF
Apply 10 kc sine wave to the Horizontal input termi 
nals. Adjust Unblanking Level Adjustment, R219, for
uniform brightness from start to finish of the trace.
Readjustment of intensity will be necessary. Switch
SWEEP SPEED switch to 20 MILLISECONDS/CM.
Turn HORIZ. POS. to each extreme. It should be
possible to bring the starting point and the 10cm point
of the sweep to center screen.
p. Common-mode Rejection
Set VERT. SENSITIVITY switch to 10 MILLI-
VOLTS/CM
VERT. SENSITIVITY VERNIER control to CAL
SWEEP TIME to 0. 5 MILLISECONDS/CM
Check balance of vertical amplifier (par. 4-10A).
Apply Ike sine wave from ($j)200CD to Vertical input
terminals through a ($)350B Attenuator with 600 ohm
termination. With the 200CD at maximum output,
switch in attenuation until 1cm of signal is displayed.
Change input to balanced (remove jumper) and feed
same signal into both grids. Remove attenuation until
a 1cm of deflection is again achieved. The attenuation
removed should be greater than 40 db.
q. Interference
Set VERT. SENSITIVITY switch to 10 MILLI-
SECONDS/CM
VERT. SENSITIVITY VERNIER to CAL.
SWEEP TIME switch to 10 MICROSECONDS/
CM
SYNC switch to INT
TRIGGER LEVEL control to INT
Apply 100 kc square wave signal to ext. sync termi 
nal from 600 ohm output of <^211A with output turned
to maximum. Put open shielded 3/4 ” plug on vertical
input terminal. Observe amplitude of interference in
vertical pattern. Maximum allowable is 0. 3cm.