TM 9-6625-1753-14
C3
Table 2-2.1. Dual Trace Plug-In 79-02A, Controls, Indicators, and
2-6. Delaying Sweep Plug-in, Controls and Indicators
Connectors (Fig. 2-6) - Continued
Table 2-3. Delaying Sweep Plug-In, Control., Indicators, and Connectors
Key
Control, Indicator or Connector
Function
68,
DC-AC-GND switch
This three-position slide switch provides the follow-
73
ing connections:
Key
Control, Indicator or Connector
Function
DC: The signal connected to the 1 MEG 14 PF
NORMAL AND DELAYING
connector is connected through a resistor to the
TRIGGERING controls:
channel amplifier
36
LEVEL control
Selects specific voltage (10 volts) which the trig-
AC: A capacitor is connected between the input
gering signal must exceed before the sweep fires.
signal and the channel amplifier.
36
PULL EXT 10 switch
Extends the range of the voltage (100 volts) which
GND: The input to the amplifier is grounded.
the triggering signal must exceed before the sweep
(The GND position may be used to establish a
fires.
reference level.)
33
AUTO-NORM switch (on older
Selects mode of operation for normal sweep.
55,
DC BAL control
A screwdriver adjustment to prevent displacement of
version model 74-13A)
NORM: Requires an input signal from dual trace
64
the trace when the VARIABLE control is operated.
plug-in to fire sweep.
70,
GAIN ADJ control
A screwdriver adjustment for setting the calibrated
AUTO: Automatic trigger circuit is activated, gen-
76
vertical deflection sensitivity.
erating a trigger pulse to fire the sweep. Input
60
MODE switch
The switch selects any of the following modes:
signal from dual trace plug-in is not required.
CH1: Only the signal applied to the upper ampli-
34
HF STAB control & NORM-RECUR
Selects recurrent operating mode for normal sweep.
fier is displayed.
switch (on older version 74-13A)
Varies the natural repetition rate of the recurrent
CH2: Only the signal applied to the lower ampli-
normal sweep, providing stable synchronization of
fier is displayed.
very high frequencies (to 50 MHz).
ALT: Channel 1 and channel 2 signals are dis-
28.1
NORM-AUTO-HF RECUR switch
Perform similar function as 33 and 34 above.
played on alternate sweeps.
(on newer version 74-13A)
"+" Position: Triggering pulse fires the normal
CHOP: Channel 1 and channel 2 signals are dis-
32
SLOPE switch
sweep on the positive-going portion of the input
played (electronic switch). The display switches
signal.
between channel 1 and channel 2 at a rate of 100
"-" Position: Triggering pulse fires the normal sweep
kHz or 1 MHz, as determined by chop rate switch.
on the negative-going portion of the input signal.
ADDED: Both channel 1 and channel 2 signals are
30
COUPLING switch
Three-position switch. Selects the following modes of
displayed at the same time. The algebraic sum of
coupling the input signal to the triggering circuit
the two signals, summed in accordance with the
in the normal sweep circuit.
polarity selected by the NORMAL-INVERT
AC: Input signal is coupled through a high-pass
switch is the resultant display.
filter having a frequency cutoff of 80 Hz.
71
NORM-INVERT switch
Selects the polarity of the displayed signal: in the
ACF: Input signal is coupled through a high-pass
75
NORM position, the waveform is displayed with
filter having a frequency cutoff of 10 kHz.
the same polarity as the input signal; in the IN-
DC: Input signal is coupled direct. This mode pro-
VERT position, the waveform is inverted.
vides optimum trigger sensitivity when very low
56,
POSITION control
Positions the trace up or down on the CRT screen.
frequency waveforms are monitored.
65
29
SOURCE switch
Three-position switch. Selects the source of the trig-
61
TRIGGER switch
Provides a choice of internal trigger sources: in the
ger.
NORMAL switch setting, the composite signal
INT: Internal trigger derived from the input
driving the vertical deflection plates is selected; in
signal.
the CH2 ONLY switch position, the channel 2
EXT: External trigger coupled through EXT
signal is selected.
TRIG connector.
58,
VOLTS, DIV switch
Selects accurately calibrated vertical deflection sensi-
LINE: Internal trigger derived from the 6.3 vac
66
tivities of 0.1, 0.2, 0.5, 1, 2, 5, 10, or 20 volts per
source. Trigger rate depends on powerline fre-
inch when the VARIABLE control is in the CAL
quency.
position.
59,
VARIABLE control
Provides variable vertical sensitivity settings and ex-
67
tends the range of the instrument to 50 volts/div.
When pulled to the PULL X10 position, the gain
25
SAW connector (banana jack)
Provides a positive saw-tooth signal of approximately
of the amplifier is increased by a factor of 10.
25 volts which is coincident with the normal sweep.
57,
UNCAL indicator
Illuminates when the VARIABLE CONTROL IS
27
''+" GATE connector (banana jack)
Provides a positive pulse of approximately 2.5 volts
63
control is set to a position other than CAL, (un-
which is time-coincident with the normal sweep.
calibrated voltage readings).
31
EXT TRIG connector (BNC connector)
Connects external trigger to normal sweep.
69,
1 MEG 14 PF connector
A BNC connector, used to connect signals to channel
DELAYING SWEEP controls:
Selects specific voltage (10 volts) which the trig-
74
1 or channel 2.
14
LEVEL control and X AMP ATTEN
gering signal must exceed before the delay sweep
control
fires. In addition, this control serves as the hor-
izontal amplifier gain control when the DISPLAY
LOGIC switch is set to X AMP.
2-2
