General Description

In the following overall functional description of the 2213 Oscilloscope, refer to the basic block diagram (Figure 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 circuitry 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 approximately 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

CH t ANO CH 2 ATTENUATORS

CH t ANO CH 2 ATTENUATORS

CH 1 ANO

CH 2 VERTICAL PREAMPS

SOURCE

MODE

AUTO

NORMAL

TV FIELD.

EXT INPUT

CH 1 ANO

CH 2 VERTICAL PREAMPS

CH 1- _

CH

2+

CH

2-

CH 1

TRIG

CH 2

CH 1

BOTH

CH 2

CHOP

CHANNEL SWITCH ANO VERTICAL OUTPUT

VARIABLE SEC/DIV

VAR HOLDOFF

TIMING SWITCH

TRIGGER

X-AX1S SIG

TRIG SIG

AUTO BASE LINE

HORIZONTAL MOOE

NO DLY.

INTENS.

DELAY TIME

MULTIPLIER

AUTO I

SWEEP GENERATOR ANO Z-AXIS LOGIC

ALT SYNC

Z-DRIVE.

SWP DUTY

INTENS LEVEL

AUTO INTENSITY

BEAM FINO

VERTICAL SIG +

VERTICAL SIG -

CH 1

VERT

MOOE

CH

TRIGGER SOURCE

CRT V870

BEAM FIND

XY AMPL/ HORIZ OUTPUT

HORIZ

HORIZ

PROBE ADJUST

CRT ANODE

AUTO INTENSITY AND Z-AXIS

Z-DRIVE

INTENS

Z-DRIVE

INTENS

AUTO INTENSITY AND Z-AXIS

FOCUS

INTENSITY

CATHODE

LINE TRIGGER

FOCUS

INTENSITY

CATHODE

LV TO ALL BLOCKS

3827-11

Figure 3-1. Basic block diagram of the 2213 Oscilloscope.

circuit functions to either produce no delay, display an intensified zone on the Sweep display, or to delay the start of the Sweep for a period of time after receiving a triggering signal. The delay time is established by two front-panel controls: the DELAY TIME switch which sets the basic delay, and the MULTIPLIER potentiometer which increases the basic delay by a factor of up to twenty times. Output signals from the Delay circuit are applied to a logic gate circuit to control both the timing of the start of the sweep and the Z-Axis drive.

The Z-Axis drive from the Sweep Logic circuit is applied to the Z-Axis amplifier. The output signal from the Z-Axis Amplifier circuit sets the crt intensity. A Chop Blanking signal from the Chop Oscillator circuit blanks the crt display during the transition between the vertical channels when using CHOP VERTICAL MODE.

The DC Restoration circuit raises the output level of the Z-Axis Amplifier to allow it to be coupled to the crt control grid. Direct coupling is not employed due to the amplitude of the voltage levels applied to the crt elements.

The Swp Duty signal from the Sweep Logic circuit is applied to the Auto Intensity circuit. The Auto Intensity circuit provides partial control of the intensity of the display when switching between different positions of the SEC/DIV switch.

The Power Supply provides all the necessary operating voltages for the instrument circuitry. Operating potentials are obtained from a circuit composed of the Preregulator, Inverter and Transformer, and Rectifiers and Filters. The Preregulator produces approximately +45 V from the ac-power-input source which is used to drive the 20-kHz Inverter stage. The Transformer secondary windings provide various ac levels that are rectified and filtered to produce the operating voltages. A High-voltage Multiplier circuit produces the accelerating, focus, and cathode potentials required by the crt.

A front-panel PROBE ADJUST output is provided for use in adjusting probe compensation. The voltage at the PROBE ADJUST connector is a negative-going square wave that has a peak-to-peak amplitude of approximately 0.5 V and a repetition rate of approximately 1 kHz.

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