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WESTINGHOUSE MODELS 813A, X and Y
Broadcast BC;
Medium Wave ,MW;
Shcrt llave SW ;
...
Intermediate
Frequency...
Radio trun Complement:
(1) W
-6L7.
_.
(2) W -6J7
(3) W-tK7
(4) W -6H6
ELECTRICAL SPECIFICATIONS
First
Det.
Oscillator
Intermediate Amplifier
Second Det.-A.V.C.
Pilot Lamps (2)
..
Power Ripply Rating.
Potree Output Rating:
Undistorted
Maximum
Cabinet Dimensions
Height. _.
_...
Width
Depth.... _......... _.... _.
Weights
(Shipping)......
Operating
Controls.
Tuning Drive
Ratioº..
..... __
530-1720 kc.
..
..
...
1720-5500 kc.
._.5500-18000 kc.
(5) W -6F5
16) W
-6F6....
!7) W -5W4
(8) W
-6E5._..
Alignment Frequencies
600 kc. (osc.,) 1500 kc. (osc., ant.)
5000 hr. (osc. ant.)
..........
17000 kc. (osc. ant.)
...............460 kc.
First A.F. Stage
....Power Output
Full -wave Rectifier
Tuning Indicator
Mazda No. 46, 6.3 volts, 0.25 amperes
........105-125 volts, 25-60 cycles, 80 watts
Loudspeaker:
2.0 watts
Type
..
.....
..........Electrodynamic
3.0 watts
Voice Coil Impedance
.. 1.8 ohms at 400 cycles
MECHANICAL SPECIFICATIONS
Model 813A
24
inches
_..
__.
93.1 inches
40
pounds
(I) Speech, Music and Power Switch
(2) Tone;
(3) Tuning;
Model 813%
Model 813Y
40
inches
40 inches
23
inches
23 inches
16% inches
12 inches
92
pounds
75 pounds
(4) Range Selector;
(5) Volume
18 to l and 90 to 1
CIRCUIT ARRANGEMENT
Radiotron W -6L7, which is particularly designed to give high
efficiency and stability as the first detector is employed for this
purpose. A separate oscillator tube, W -6J7, is also used.
The R.F. coil system is greatly simplified in comparison to
previous years.
The antenna coil consists of only four windings
to cover three ranges.
By referring to the schematic circuit
diagram it will be noted that by an extremely simple switching
circuit coil L-1 is used only as the short wave secondary coil;
coil L2 is used (depending on the switch position) as either the
short w ve primary winding or the medium wavesecondary
winding; coil L-3
is used either as the broadcast secondary
winding or the medium wave primary winding; roil L-4 is the
broadcast primary winding only.
The oscillator coil system uses three only, tapped windings in
the well known Hartley circuit.
The unused lower frequency
windings are shorted out by means of the shorting bars on the
range selector switch.
Alignment Procedure
1-F Core Adjustments:
The four adjustment screws (attached to molded magnetite
cores) of the two i -f transformers are located one on top and one
on bottom of each i -f transformer. Each circuit must be aligned
to a basic frequency of 460 kc. To do this, attach the output
indicator across the loudspeaker voice coil.
Connect the output of the test oscillator to the control grid
of the W -6L7 through a .05 mfd. capacitor.
Connect the test
oscillator ground terminal to the ground terminal of the receive
chassis.
Tune the oscillator to 460 kc. Advance the receiver
volume control to its full -on position and adjust the receiver
tuning control to a point, within its range, where no interference
is encountered either from local broadcast stations or from the
heterodyne oscillator. Increase the output of the tent oscillator
until a alight indication is present on the output indicator.
Adjust the two magnetite core screws of the second i -f transformer
to produce maximum (peak) indicated receiver output.
Then
adjust the two magnetite core screws of the first i -f transformer
for maximum (peak) receiver output as shown by the indicating
device.
During these adjustments, regulate the test oscillator
output so that the indication is always as low as possible.
By
doing so, broadness of tuning due to a.v.c. action will be avoided.
It is advisable to repeat the adjustment of all i -f magnetite core
screws to assure that the interaction between them has not dis-
turbed the original adjustment.
Broadcast Trimmer Adjustments:
Calibrate the tuning dial by setting the pointer to the angle
of the border line of the dial immediately below the 530 ho.
calibration point, with the two -gang tuning condenser in full
mesh.
The output indicator should be left connected to the
system.
Connect the test oscillator to antenna and ground
terminals of the chassis through a 200 mmfd. condenser. Adjust
the test oscillator to 1500 kc. and set the receiver tuning control
to a dial reading of 1500 kc. Leave the volume control of the
receive( at its maximum position. Make sure that the Range
Selector is at its broadcast position. Regulate the output of
the test oscillator until a slight indication is perceptible at the
receiver output.
Then adjust the two 1500 kc.
trimmers
(see diagram) of the oscillator and antenna transformer coila
so that each produces maximum (peak) receiver ouput.
After
this maximum has been accurately obtained, shift the test
oscillator to 600 kc. Tune the receiver to pick up this signal,
disregarding the dial reading at which it is beet received. Then,
adjust the receiver 600 kc. series trimmer. C16, simultaneously
rocking the tuning control backward and forward through the
signal until maximum receiver output results from these com-
bined operations.
The adjustment at 1,500 he. should then be
repeated to correct for any change which may have been caused
by the oscillator series trimmer adjustment.
"Medium Ware" Trimmer Adjustments
Use the same equipment and layout as for broadcast trimmer
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SWITCH SECTIONS ARE SHOWN
IN
M.W. POSITION
Range Selector Diagram
OUTPUT TRANSE
Reproducer Wiring Diagram
adjustment. Place receiver range selector to its "medium wave"
position with the receiver dial pointer set to 5000 ke. Tune the
test oscillator to 5000 kc.; adjust the two air dielectric trimmers
(see diagram) for maximum output. Two peaks may be found
on the oscillator trimmer. The peak obtained with minimum
capacity (plunger nearly out) should be used.
"Short Wave" Trimmer Adjustments
Leave the equipment set up the same as for the broadcast
trimmer adjustment except that the output of the test oscillator
to the antenna terminal of the receiver should be connected
through a 400 ohm resistor. Set the receiver range selector to its
"short wave" position and dial pointer to 17,000 kc. Tune the
test oscillator to 17,000 ho. Adjust the oscillator 17,000 kc.
trimmer (see diagram) for maximum output.
Two peaks may
be found.
The peak with minimum capacity (plunger nearly
out) should be used. Adjust the antenna 17,000 let. trimmer
until maximum output is reached, while slightly rocking the
gang tuning condenser back and forth through the signal.
Two
peaks may be found with this
circuit.
cuit.
The peak with maxi)
mum capacity (plunger nearly in) should be used. Check the
image frequency by changing the receiver dial setting to 16,080
kc.
The test oscillator signal should be faintly received at this
position, indicating that the adjustment of the oscillator 17,000
ku. trimmer has been correctly made. No adjustment should be
made while checking for this image signal.
Loudspeaker:
The reproducer centering adjustment will be obvious if the
field coil shield is removed.
One screw in the centre of the back
of the reproducer holds the shield in place. Two screws hold
the voice coil centering spider in place and must of course be
loosened while adjustment is being made.
SEE
MODEL 512
R.F. Alignment Points
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