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Description
The RCA WO-33A is a 3-inch oscilloscope de-
signed for "on-location" and service-shop use in
servicing color and black-and-white television re-
ceivers, Hi-Fi equipment, PA and sound reenforcing
systems,broadcast station and remote equipment,
communications and industrial electronic equipment.
A novel feature of the WO-33A is the Vertical
Input Attenuator which automatically switches the
amplifier from Wide Band to Narrow Band when
in the three highest gain positions.
Another important feature of the WO-33A is
the exceptionally high gain in its vertical amplifier.
There is enough sensitivity to provide a useful dis-
play of signals from low-level microphones, phono-
pickups and other weak signals found in radio/TV
receivers, audio amplifiers, etc.
A voltage-calibrated, frequency-compensated ver-
tical-input attenuator, an internal calibrating-voltage
source, and a graph screen scaled directly in volts
make it possible to use the WO-33A as a visual
voltmeter. The unique system of calibrating the
graph screen provides for scaling voltages directly
from the screen. The measurement procedure is very
similar to that employed with a vacuum-tube volt-
meter. A calibrating voltage is automatically applied
to the vertical amplifier when the bandwidth control
is set to the calibration position. This switch also dis-
connects internally the input and attenuator circuits,
making it unnecessary to remove leads and probes
from the external circuit under test. These unique
facilities make voltage calibration and measurement
a simple, almost automatic procedure.
The sweep-frequency control
is continuously
adjustable from 15 cps to 75 Kc. The sweep oscil-
lator has excellent stability at high sweep rates, a
fast retrace, and adequate linearity throughout its
frequency range. The over-all frequency range of
the oscillator is divided into four basic ranges; a
vernier adjustment, which overlaps the basic sweep
ranges, provides exact adjustment of the sweep fre-
quency. The amount of sync signal fed to the sweep
oscillator may be adjusted by means of a front-panel
• 4 •
control.
Sweep synchronization is
exceptionally
stable throughout the sweep range of the oscillator.
A phase control is provided for varying the phase
of the internal sweep voltage when the "LINE"
position of the H/SWEEP SEL cOlltrol is used, en-
abling the WO-33A to be phased with an external
line-frequency sweep oscillator.
To facilitate its use, the WO-33A is equipped with
a specially designed single-unit probe and input
cable. This accessory, the WG-349A DirectiLow-
Capacitance Probe and Cable, is provided with a blue
input lead and a yellow input lead. When the blue
input is used, the test signal is fed directly to the
vertical-input terminal. When the yellow input is
used, a special high-impedance circuit in the probe
is connected in series with the test point and the
'scope. This high-impedance circuit presents an over-
all input resistance of 10 megohms and an input
capacitance of approximately 10
ppf
to the test cir-
cuit. This feature reduces circuit-loading effects and
permits use in circuits which would not function
properly if loaded down by a conventional oscillo-
scope.
The WO-33A can be used to trouble-shoot and
signal trace all sections of both black-and-white
and color-TV receivers. The voltage-calibrating facil-
ities, wide band-pass, and high-impedance input
characteristics make possible observations and meas-
urements of color-burst signals and othe'; critical, ,.
high-frequency waveshapes in circuits which are
sensitive to loading effects.
The size and weight of the WO-33A make it an
especially portable instrument, useful in such appli-
cations as industrial maintenance and trouble-shoot-
ing, general waveform analysis, adjustment of radio
receivers and transmitters, square-wave and general
testing of audio equipment, peak-to-peak voltage
measurements, and observation of vacuum-tube
characteristics. The WO-33A is a versatile and re-
liable instrument, well suited to applications which
require a dependable oscilloscope.
Specifications
NOTE: Performance figures are for a line voltage of 117 volts, 60 cps.
Frequency Response:
Electrical
Vertical Amplifier:
Wide-Band Positions (5.5 cps to 5.5 Mc)
..................................................... flat within - 3 db
High-Sensitivity Positions:
20 cps
to
150 Kc ..................................................... .
3 cps to 1.5 Mc .................................................... .
Horizontal Amplifier (3.5 cps to 350 Kc)
Deflection Sensitivity:
Vertical Amplifier:
At V INPUT connector
.......................................
With WG-349A Blue Lead
With WG-349A Yellow Lead
..............
(Wide-Band)
Positions
rms
p-p
0.10
0.3
0.10
0.3
1.0
3.0
. ..... flat within - 3 db
flat within - 6 db
.... flat within - 6 db
(High-Sensitivity)
Positions
rms
p-p
.003
0.01
volt/in
.003
0.01
volt/in
.03
0.1
volt/in
Horizontal Amplifier (at H INPUT terminal)
Rise Time (Vertical Amplifier):
.......................................................................................... 0.9 rn1S volt/in
5.5-Me Positions
0.1 psec
Input Resistance and Capacitance:
Vertical Amplifier:
At V INPUT connector ......................... ................. ............... ......................
1 megohm shunted by approx. 50
f.Lpf
With WG-349A Blue Lead ...................... ....... ........
........ ...... ... ... ...... 1 megohm shunted by apf)fox. 90
f.Lf.L f
\Vith \VG-349A Yellow Lead ....................
. ................................. 10 megohms shunted by ap~rox. 10
pf.Lf
Horizontal Amplifier (at H INPUT terminal)
....................................................
. .....
io
megohms
EXT SYNC Input Terminal........................
. .................................................................... 250 K to 55 K
Sweep Oscillator:
Frequency Range (continuously adjustable)
Sync
................................... .
Sync Range.
Maximum AC Input Voltage (at Lo-Cap Probe):
(In presence of 400 volts dc) ............................ .
Phase-Control Range .............................................. .
Power Requirements:
Voltage ....
Average Power Consumption .................................... .
1-6BR8
1-6BK7A
Tube Complement
2-12AT7
Height
Width
1-6X4
Mechanical
8
31f1
14
6
1111
12
• 5 •
Length
Weight
15 cps to 75 Kc
........................ External;
±
Internal
... To
4.5 Mc
..... 600 p-p volts
o
to 160 degrees
105-125 volts, 50-60 cps
. ........... 50 watts
1-6C4
1-3AQPl
....... lOW'
14 lbs
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