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CHANGES IN LATER PRODUCTION WESTINGHOUSE MODELS 527, 622
Some of the later production of Model 527 used transformers designed for 110 volt, 60 cycle power
lines only.
These transformers are not mechanically interchangeable, and if it is necessary to change one of
these 60 cycle chassis to operate on 25 cycle, it will be necessary to cut or drill the chassis frame to fit 25-60
cycle transformers.
The style number follows:
Model 527 - 60 cycle, 110 volt Power Transformer, S. No. H-38247.
List Price
.
.
.
.
$5.25
Later production on mantel Models 527-A and 622-A use a new reproducer which is marked "H-38261."
Parts for this reproducer are not interchangeable with reproducers marked "H-34495,"
ALIGNMENT PROCEDURE
There are various alignment trimmers provided in the antenna
transformer and oscillator coil tuned circuits. One adjustment is
also provided for the wave trap. The i -f transformer adjustments
are made by means of screws attached to molded magnetite cores.
All of these circuits have been accurately adjusted during manu-
facture and should remain properly aligned unless affected by
abnormal conditions or altered during servicing. Loss of sens-
itivity, improper tone quality, and poor selectivity are the
usual
indications of improper alignment.
The correct performance of this receiver can only be obtained
when the aligning has been done with adequate and
reliable
apparatus.
It is not necessary to use a frequency modulated
oscillator and cathode ray oscillograph to align this
receiver.
Those service men that have this equipment will probably
prefer
to use it and for their convenience we have indicated on the socket
voltage diagram the proper connection point for the cathode ray
vertical amplifier input terminal.
By using the Cathode Ray Adapter shown in the Re-
placement Parts List the cathode ray connection; m;y
be
made without removing or opening the chassis.
A test oscillator is required as a source of the specified
align-
ment frequencies. Visual indication of receiver output during the
adjustment is necessary and should be accomplished by the use
of an indicator or meter.
The procedure outlined below should be followed in adjusting
the various trimmer capacitors and molded cores:
Calibrate the tuning dial by adjusting pointer to the
low
frequency end of scale with gang condenser plates fully
meshed.
The pointer should be horizontal with its painted section
resting
at the end of the vertical index line. This is a friction adjustment.
At the same time set the vernier dial scale (this is secured by two
set screws) to read "o".
Perform alignment in proper order as shown by the accom-
panying chart, starting with No. 1, and following all
operations
across, then No. 2, etc. The chassis bottom shield must be
s.curely in place when making R.F. adjustments. Adjustment
locations and frequencies are shown on a sticker fastened to the
b:,t tom side of the chassis shield.
These trimmer locations are
also shown in one of the accompanying illustrations.
Connect the "low output terminal of the test oscillator to the
receiver chassis for all alignment operations. Regulate the output
of the test oscillator so that minimum signal is applied to
the
receiver to obtain an observable output indication.
This will
avoid a -v -c action.
The term "Dummy antenna" means the device which must be
connected between the "high" test -oscillator output terminal and
the point of connection to the receiver in order to obtain ideal
alignment. "No signal, 550-750 kc." means that the receiver should
be tuned to a point between 550 and 750 kc. where no signal or in-
terference is received from a station or the receiver (heterodyne)
oscillator.
The term "Rock Through" indicates that the receiver station
selector should be rocked back and forth while making the
indicated adjustment. The adjustment and rocking should be
cóntinued until the combined action results in the maximum
deflection on the output meter.
When adjusting oscillator circuits that have both series and
shunt trimmers it is good practicé to repeat the adjustment on
the oscillator shunt trimmer after making the adjustment on the
oscillator series trimmer. On some tuning ranges it is found that
more than one peak may be secured if the trimmer is adjusted
over a wide enough range. When this occurs it should be noted
that oscillator circuits should be aligned, using that peak which
occurs at the lower capacity setting of the trimmer. On R.F. or
first detector trimmers the peak occurring with the larger capac-
ity setting of the trimmer should be used.
It is also good practice to make sure that the trimmers on the
short-wave ranges are set so that the oscillator stage develops its
signal at a higher frequency than the signal to which the R.F.
stage for stages) is tuned. This check can be made by advancing
the test oscillator output control and tuning the receiver above
and below the frequency of the test oscillator, noting at what
frequency the test signalreappears.
It should reappear at a
frequency setting on the receiver dial lower than the test oscillator
frequency by an amount equal to twice the intermediate fi equency.
Due to the small number of trimmers on the Model 622, it may
occasionally be necessary to Set the trimmers that are available in
a position so as to compromise between maximum sensitivity and
absolutely correct dial setting.
It may also be necessary to
replace a coil assembly if due to accident serious misalignment
occurs which cannot be corrected by the trimmers available.
It is possible to use a tuning wand (such as stock RCA -6679) in
the usual way as a check-up on coil alignment, but in order to do
this it will be necessary to drill two openings in the chassis shield
to permit insertion of the tuning wand into the coils under
operating conditions.
This check with the tuning wand should
be made in all cases before replacing any coil assemblies.
R.F. Coil System, Model 622
This circuit also uses a Radiotron W -6A8 as both first detector
and oscillator, with separate coil assemblies for each. The an-
tenna 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-2 is used only as
the short wave secondary coil; coil L-3 is used (depending on the
switch position) as either the short wave primary winding or the
medium wave secondary winding; coil L-4 is used either as the
broadcast secondary winding or the medium wave primary
winding; coil L-5 is the broadcast primary winding only.
The oscillator coil assembly uses three separate windings in the
grid circuit and three separate windings in the plate circuit. The
unused lower frequency windings are shorted out by means of the
shorting bars on the range selector switch.
It will be noted that there are only three R.F. trimmers
(ex-
clusive of the wave trap adjustment). One is used to align the
short wave antenna coil with the'oscillator coil. No trimmers
are
used in the medium wave band. The remaining two are the
oscillator, 1500 kc. and the oscillator, 600 kc., trimmers used to
align the oscillator broadcast range circuit with the antenna coil
and dial scale.
Reference to condenser C-6 on the schematic diagram 'gives an
excellent illustration of how the utmost in economy, consistent
with outstanding performance, is applied to the design of these
receivers.
This condenser is located to take adyantag_e of the
existing range switching system. It will
be
noted that in the
short wave position of the range selector, condenser C-6 adds its
capacitylin parallel with. condenser C-3, to aid in securing align-
ment.
In the broadcast position of the range selector, this con-
denser is
(neglecting the small inductance of the coil L-2 at
broadcast frequency) in parallel with the oscillator tuned circuit
and aids in securing alignment.
Due
to precision manufacturing it has been found possible to eliminate
all but three of the customary R.F. trimmers, and two of the
trimmers used are of the air dielectric type.
W
W527 and W622
Reproducer Wiring Diagram
HUM
VOICE
SPEAKER FIELD
NEUUT..-COIL
COIL
w V W
u
J
J
Q
FED A YELLOW
m
aLUACK'
SOCKET j
\
NOTE
BLACK, YELLOW
FOR MODELS `622 K AND 622Y
ED
OUTPUT TRANSF.
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