TM 9-6625-1753-14
C1
NORMAL AND DELAYING TRIGGERING SOURCE switch ................................LINE
(5) Rotate the VARIABLE control fully clockwise until it rests in the detent position.
AUTO-NORMAL-HF RECUR Switch ..................................................................NORMAL
(6) Set the VOLTS/DIV switch to a position that will display the ent ire waveform on the screen. Start with the
VOLTS/DIV switch fully counterclockwise and rotate it in clockwise direction until the entire trace comes into view. Use the
c. Rotate the SCALE ILLUM control fully clockwise. The pilot lamp should illuminate.
POSITION control to center the trace on the screen..
d. After about 1 minute, rotate the INTENSITY control clockwise until a horizontal trace appears on the screen. If a trace
(7) If voltages are not to be measured, you may rotate the VARIABLE control counterclockwise to reduce the display
doesn't appear, check the beam position indicators on the dual trace plug-in (press the BEAM FINDER on the dual trace plug-
height. To make the display occupy as much of the vertical area as possible, rotate the VOLTS/DIV switch to the position that
in 79-02A) and the delaying sweep plug-in. If one or more of these lamps are glowing, the trace is off the screen in the
just puts the top and bottom of the waveform off-screen. Bring the whole track back into view by rotating the VARIABLE
direction indicated by the arrow adjacent to the glowing lamp.
control counterclockwise.
e. Use the POSITION controls on both plug-in units to position the trace on the screen.
(8) To expand a selected portion of the waveform vertically, rotate the VOLTS/DIV switch clockwise to a more
f. Adjust the FOCUS, ASTIG, and INTENSITY controls for a sharp trace. Since these adjustments are somewhat
sensitive position. A portion of the waveform may be off the screen. If the portion to be observed is not on the screen, bring it
interdependent, it may be necessary to readjust the FOCUS and ASTIG controls as the INTENSITY setting is changed
back by moving the waveform up or down, as required, with the POSITION control.
(9) Invert the display with the NORM-INVERT switch. In the NORM segment of the switch, p sitive-going pulses
o
appear as positive-going pulses on the screen. In the INVERT segment of the switch, positive-going pulses appear as
Caution: The trace can damage the cathode-ray screen if the INTENSITY control is advanced too far on slow-
negative-going pulses on the screen.
moving sweeps, or if the trace is allowed to contract to a spot. The INTENSITY control should be adjusted until the
b. Dual Trace Presentation. To display two waveforms, connect the probes from both channel inputs to the points to be
trace can be viewed comfortably. Rotate the INTENSITY control until the trace is dim or turned off when the
measured.
oscilloscope is to be left unattended.
(1) Use the CHOP mode for displaying continuous waveforms at slow sweep speeds (less than 1 millisecond per
division). This mode eliminates most of the flicker present with alternating sweeps at slow speeds. To prevent the sweep
2-8. Use of Probe
from triggering on the chopping signal an external trigger is preferred.
a. Set up the probe for use as follows:
(2) Square wave or sharp pulses at slow speeds may be difficult to synchronize in the CHOP mode. For these
(1) Connect the probe to the channel A or channel B input BNC connector, as desired.
waveforms, if the display is not stable in the CHOP mode, set the MODE switch to ALT or use an external trigger.
(2) Set the following controls to the indicated position.
(3) Use the ALT position of the MODE switch for all sweep speeds faster than 1 millisecond per division, and for all
triggered modes of operation.
VOLTS/DIV switch to .02 (0.1-MH/F model)
(4) To display the algebraic sum of two signals, set the MODE switch to A + B (ADDED). Both channel A and B
NORM-INVERT switch (and AC-DC-GND switch) to NORM-DC
NORMA-INVERT switches are set at NORM. For A-B presentation (algebraic difference of two signals), set the channel A
MODE switch to the channel selected
NORM-INVERT switch to NORM and the channel B NORM-INVERT switch to INVERT. For a B-A presentation, set thee
TIME/'DIV switch to 5 mSEC at 60 cycles, 1 mSEC at 400 cycles
channel A NORM-INVERT switch to INVERT and the channel B NORM-INVERT switch to NORM.
(3) Touch the probe tip to the CAL 1V connector. Several cycles of the calibration signal waveform (square wave)
2-10. Operation of the Delaying Sweep Plug-IN
will be displayed on the screen.
(4) Note the shape of the square wave. If it is not flat on top and bottom, adjust the capacitor in the body of the
a. General Triggering Information. Since the triggering circuits of the normal and delayed sweep channels are similar,
probe. To do, this, first rotate the grooved locking device counterclockwise until it turns freely. Next rotate the body of the
the controls described in the following instructions will pertain to both channels.
probe until the top and bottom of the square wave is flat. Finally, rotate the grooved locking device clockwise until it call no
(1) Triggering sources for normal and delayed sweeps . You can select three sources of trigger pulses for the normal
longer turn. (You may have to, repeat this procedure several times to obtain the required results.)
or delayed sweep with the SOURCE switch: LINE (frequency depends on power-line frequency), EXT. (any signal connected
b. Be careful in selecting the measuring point. Although the oscilloscope has a high input impedance and the probe
to the EXT TRIG connector), INT. (a sample of the input signal).
increases the input impedance from 1 to 10 megohms, the source response may suffer if the probe is connected to a high-
(a) LINE. Use the LINE position to observe signals that recur at the rate of the power source and when no other
impedance source. To avoid this, make your measurements at the cathode of a stage instead of the grid or plate whenever
triggering source is available.
possible.
(b) EXT. To use external triggering, connect the probe between the trigger source and the EXT TRIG connector.
c. When amplitude measurements are made with the probe, multiply the observed amplitude by the factor marked on
Use external triggering under the following conditions:
the probe (X10).
1.
To synchronize the display with a signal in the equipment under test.
2. To synchronize a slow-changing waveform, which is difficult to trigger internally, when a suitable
triggering waveform (sharp pulse or square wave) is available at the same frequency, or a multiple or submultiple of it.
2-9. Operation of the Dual Trace Plug-In
3. To compare the phase difference or time lag between two signals. Use one of the signals as the trigger
You can use the two-channel dual trace plug-in for single or dual-channel display. All the controls covered below are located
source. The distance from the start of the trace to the start of the waveform is a measure of the time delay. For direct
on the dual trace plug-in 76-02A or 79-02A front panel.
comparison, both signals may be displayed in dual-trace operation. Either CHOP or ALT position of the MODE switch will
work.
a. Single Trace Presentation.
(c) INT. Use the INT position if the input signal itself has sufficient amplitude to trigger the sweep. This is a
(1) Rotate the MODE switch to channel A or B (CH1 or CH2)
convenient method of triggering connections are required. When the dual trace plug-in 79-02A is used, the TRIGGER switch
(2) Connect the probe to the signal source.
provides two selections of trigger sources in INT operation. The channel 2 signal (CH2 ONLY setting) or the composite signal
(3) Set the NORM-INVERT switch (and the AC-DC-GND switch) to NORM-DC.
(NORMAL) may be selected.
(4) If the waveform to be o served contains an undesirable dc component, set the NORM-INVERT (AC-DC-GND)
b
switch to NORM-AC.
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