Theory of Operation—2213 Service
GENERAL DESCRIPTION
In the following overall functional description of the
2213 Oscilloscope, refer to the basic block diagram (Fig
ure 3-1) and to the detailed block diagram (Figure 9-4)
located in the "Diagrams" section of this manual. In
Figures 3-1 and 9-4, the numbered diamond symbol in
each major block refers to the appropriate schematic
diagram number.
Signals to be displayed on the crt are applied to either
the CH 1 OR X input connector or the CH 2 OR Y input
connector. The signals may be coupled to the attenuator
circuit either directly (DC) or through an input-coupling
capacitor (AC). The input may also be disconnected and
the input to the attenuators grounded when the GND
position of the coupling switch is used. In the GND
position, the ac-coupling capacitor is allowed to precharge
to the dc level present at the input connector. This pre
charging prevents large trace shifts of the display when
switching from GND to AC coupling.
Each channel output signal from the Attenuator cir
cuitry is applied to the Vertical Preamplifier circuitry for
further amplification. The Channel 2 Preamplifier includes
an Invert feature that allows the operator to invert the
Channel 2 signal display on the cathode-ray tube (crt).
Trigger Pickoff Amplifiers in each channel supply an
internal trigger signal from either channel signal or from
both channels to the Internal Trigger Amplifier in the
Trigger circuitry.
Each channel signal is selected for display in turn by the
Channel Switching Logic circuit under control of the
front-panel VERTICAL MODE switches. The output signal
from
the Channel Switching Logic circuit is applied to a
Diode Gate circuit. The Diode Gate circuit switches either
channel signal (or both signals for ADD) to a Delay Line
Driver stage that supplies the proper drive and impedance
match to the Delay Line. The Delay Line produces approx
imately 100 ns of delay in the vertical signal to allow the
Horizontal circuitry time to produce the necessary sweep
to display the signal.
Final amplification of the vertical signal is supplied by
the Vertical Output Amplifier. The Vertical Output
Amplifier supplies the required signal levels necessary to
produce vertical deflection of the electron beam in the crt.
The Trigger circuitry uses either the Internal Trigger
signal derived from the input signal(s), an External Trigger
signal, or a Line Trigger signal obtained from the ac-power-
source input waveform to develop the triggering signal for
the Sweep Generator. An Auto Trigger circuit ensures that
the range of the TRIGGER LEVEL control conforms
approximately to the peak-to-peak amplitude of the trigger
signal when either AUTO or TV FIELD TRIGGER MODE
is selected. In NORM MODE, the TRIGGER LEVEL
control must be adjusted for the correct trigger signal level
before a sweep can be generated.
A TV Field sync circuit provides stable triggering on
television-signal vertical-sync pulses. Triggering at the
television line rate is accomplished when either AUTO or
NORM MODE is used.
The Sweep Logic circuit controls the generation of the
sweep and the unblanking of the Z-Axis Amplifier for the
Sweep display. When the TRIGGER MODE switch is
set to either AUTO or TV FIELD and no trigger signal is
present, the Auto Baseline circuit causes the Sweep Logic
circuit to produce a sweep after a period of time. In the
NORM position of the TRIGGER MODE switch the
Auto Baseline circuit is disabled, and a sweep will not be
generated until a triggering signal is received.
The output gate signal from the Sweep Logic circuit is
applied to the Miller Sweep circuit. This circuit produces
a linear sweep output with a run-up time that is controlled
by the SEC/DIV switch. The sweep signal is applied to
the Horizontal Preamplifier for initial amplification. Final
amplification of the sweep signal to drive the crt horizontal
deflection plates is provided by the Horizontal Output
Amplifier.
The Horizontal Preamplifier gain is increased by a factor
of 10 when the X10 Magnifier feature is used. Horizontal
positioning of the display is also accomplished in the
Horizontal Preamplifier circuit.
In the X-Y Mode of operation the CH 1 signal, via the
Internal Trigger circuitry, is applied to the XY Amplifier
where it is amplified for application to the Horizontal
Preamplifier. In this operating mode, the CH 1 Internal
Trigger signal supplies the horizontal deflection to the crt,
and a sweep signal is not produced by the Miller Sweep
circuit.
The HORIZONTAL MODE switch (NO DLY, INTENS,
and DLY'D) controls the action of the Delay circuit. This
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