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WESTINGHOUSE MODELS e121.-1 and 521X
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Alignment Procedure
There are three 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 manufacture and
should remain properly aligned unless affected by abnormal
conditions or altered during servicing. Loss of sensitivity,
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 fre-
quency modulated oscillator and cathode ray oscillograph to
align this receiver. Those service men that have this equip-
ment 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 connections may be
made without removing or opening the chassis.
A test oscillator is required as a source of the specified
alignment frequencies. Visual indication of receiver output
during the adjustment is necessary and should be accom-
plished by the use of an indicator or meter.
The procedure outlined below should be followed in
adjusting the various trimmer capacitors and molded cores:
I -F Core Adjustments:
The four adjustment screws (attached to molded
mag-
netite 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 -6A8 through a .05 mfd. capacitor.
Connect
the teat oscillator ground terminal to the ground
terminal
of the receiver 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 test oscillator until
a
slight
O
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 trans-
former 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 disturbed the original
adjustment.
R.F. Trimmer and Wave Trap Adjustments:
Calibrate the tuning dial by setting the pointer to the end
of the border line of the dial immediately below the 530 kc.
calibration point, with the 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.
For best results, the wave trap should be properly tuned
before making the final adjustment to
the other R.F.
trimmers.
The wave trap is tuned by an adjustable iron
core and is normally tuned to 460 kc. Should it be neces-
sary at any time to retune it to 460 kc., set the test oscil-
lator to deliver a frequency of 460 kc. and very carefully
adjust the wave trap (using trimmer tool H-29643) until
minimum output
is
obtained on the
output indicator.
Should local conditions be such that interference is gener-
ated at some other frequency within the range of 415 to
485 kc., it is possible to tune the wave trap to the interfering
frequency to secure minimum interference.
The antenna and oscillator trimmer adjustments may now
be made.
Tune 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 receiver at
its maximum position.
Regulate the output of the test oscillator until a slight
indication is perceptible at the receiver output. Then adjust
the two trimmers, C8 and C2, of the oscillator and antenna
transformer coils (mounted on the variable condenser) so
that each produces maximum (peak) receiver output. 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 best
received.
Then, adjust the receiver oscillator series trim-
mer, C10, simultaneously rocking the tuning control back-
ward and forward through the signal until maximum re-
ceiver output results from these combined operations.
The
adjustment at 1,500 kc. should then be repeated to correct
for any change which may have been caused by the
oscillator series trimmer adjustment.
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