Sect. III Page 1
SECTION Ill
THEORY OF OPERATION
3-1 OVER-ALL OPERATION fier for internal synchronization, from the EX?.
SYNC INPUT or from an internal power line
The block diagram in Figure 3-1 shows the basic source. The Sync Circuit amplifies all input sig-
signal circuits in the Model 150A Oscilloscope: the nals, and determines the level and polarity which
Vertical Amplifier, Horizontal Amplifier, Sweep will start a sweep.
Generator and Cathode Ray Tube.
d. Sweep Generator - The Sweep Generator starts
a. Vertical Amplifier - The complete vertical am- on receiving a sync pulse from the Sync Circuit
plifier receives the input signal, amplifies it, and generates a sawtooth to drive the Horizontal
and drives the vertical deflection plates. It pro- Amplifier. The Feedback Integrator determines
vides attenuation of the input signal if necessary; . the basic sweep time per centimeter, and the
determines the direction of spot deflection for a SWEEP MODE control selects triggered or free-
given input signal polarity; determines ?the verti- running operation. A SINGLE SWEEP switch
cal position of the spot on the screen: supplies a provides either single or repetitive sweeps. The
signal for internal synchronization; and incor- sweep generator also supplies unblanking pulses
porates a 0.25 psec delay in the input waveforms. to the CRT, a timing signal (during each saw-
tooth flyback) to the Dual Channel Vertical Am-
The complete Vertical Amplifier circuit is in plifier Plug-In Unit for ALTERNATE operation,
separate parts: first the input attenuators, phase and sweep and gate signals to output connectors.
inverter, vertical position controls and ampli-
fiers in the Vertical Amplifier Plug-In Unit, and e. The CRT - The CRT is a type 5AMP - mono-
second the intermediate and final amplifiers on accelerator tube with the cathode operated at
the instrument chassis.
-4800 volts. The mono-accelerator anode makes
possible a simple astigmatism adjustment (lo-
b. Horizontal Amplifier - The horizontal amplifier cated inside the access hatch) which requires no
is driven either from the HORIZ. INPUT jack or resetting when adjusting the FOCUS or INTENS-
from the internal sweep generator. ITY. The deflection plate terminals located on
the periphery of the. tube neck are connected
through removable jumpers directly to the Main
The complete Horizontal Amplifier consists of Vertical Amplifier, Horizontal Amplifier, and
the main amplifier, and a preamplifier (used only
for external signals applied to the HORIZ. IN- Astigmatism control.
PUT connector). The preamplifier stage includes
the VOLTS/CM portion of the HORIZ. SENSITW- 3-2 VERTICAL AMPLIFIER
ITY selector switch and is not in use when the
switch is set to one of the MAGNIFICATION po-
The signal from the plug-in vertical amplifier is
sitions. The MAGNIFICATION circuit of the coupled through a connector on the plug-in unit chas-
HORIZ. SENSITIVITY selector is in the Main sis to the Main Vertical Amplifier on the instrument
Horizontal Amplifier. The sawtooth sweep is chassis .
applied directly to the Main Horizontal Amplifier
I. while external signals are first applied to the
. HORIZ. SENSITIVITY switch and the preampli-
Input amplifiers V1 and V2 provide a maximum gain
fier. ,
of approximately 20 db. The gain adjustment poten-
tiometer R5 has a range of approximately 4 db ob-
c. Sync Circuit - The Synchronizing Circuit re- tained by varying V1 and V2 cathode circuit degen-
ceives a signal either from the Vertical Ampli- eration. |
ACEC
