c. Now move the voltmeter ungrounded connection to the junction of R107 and
R108.
(R107 is connected to center arm of Delaying Sweep TRIGGERING
LEVEL control.)
Set the Delaying Sweep TRIGGERING LEVEL control so that
zero deflection is obtained even on the 3-volt range of the meter.
d. Loosen the Delaying Sweep TRIGGERING LEVEL knob on its shaft. Turn the
knob on its shaft so that its index points to "0" on the panel, and tighten
the knob. Recheck that a voltmeter reading of zero is obtained when the
knob index is at "0".
111. To adjust TRIGGERING LEVEL CENTERING.— Settings:
Main Sweep TRIGGERING LEVEL— 0.
TIME/CM— 1 millisec.
TRIGGER SLOPE— +BJT.
5X MAGNIFIER— OFF.
TRIGGERING MODE— AC SLOW.
HORIZONTAL DISPLAY— MAIN SWEEP NORMAL.
a. Display calibrator signal. Set calibrator output and the VOLTS/CM switch
for 3 or 4 mm of vertical deflection. Set Main Sweep STABILITY control and
the TRIGGERING LEVEL CENTERING control so that a stable display is obtained.
Then make further adjustments of TRIGGERING LEVEL CENTERING so that the sweep
triggers equally well on +INT and -INT settings of the TRIGGER SLOPE switch.
Note: The Main Sweep STABILITY control and the Main Sweep TRIGGERING LEVEL
control may be touched up slightly to obtain the above result. The final
setting of the Main Sweep STABILITY control will be in the vicinity of that
needed just to produce triggering. The final setting of the Main Sweep TRIG-
GERING LEVEL control will be essentially at "0". After the TRIGGERING LEVEL
CENTERING is adjusted, reliable triggering must be obtained as the TRIGGER
SLOPE switch is moved back and forth between the +INT and the -INT positions
without touching the Main Sweep TRIGGERING LEVEL or Main Sweep STABILITY
controls.
The above is a preliminary adjustment of the TRIGGERING LEVEL CENTERING con
trol. The final adjustment is described under Step 15, below.
b. Check the polarity of the TRIGGER SLOPE switch on +INT and -INT positions.
The leading edge at the left end of the graticule should be a rising edge
when the switch is in the +INT position, and it should be a falling edge
when the switch is in the -INT position.
15. To adjust TRIGGER SENSITIVITY control.— Settings of the oscilloscope being cali
brated:
Main Sweep TRIGGERING LEVEL— 0.
Main Sweep STABILITY— CCW.
TRIGGER SLOPE— +LINE.
TRIGGERING MODE— AC SLOW.
HORIZ. DISPLAY— MAIN SWEEP NORMAL
TIME/CM— 100 usee.
5X MAGNIFIER— OFF.
MULTIPLIER— XI.
INTENSITY— CCW.
Settings of test oscilloscope:
TRIGGER SLOPE— +LINE.
TIME/CM— 1 millisec.
August, 1956
FD-535-8
