CIRCUIT DESCRIPTION
Each major section of the Receiver will be
described separately in the following Circuit quency control) voltage to lock-in the local
Description. For ease of explanation, the Source oscillator frequency with the station being
switch will be described in the FM position.
Follow the circuit on the Block Diagram (foldout from Page 66) and on the Schematic (foldout from Page 79) while reading the Circuit
Description. The letter-number designations
(R4,
C115, R212) for all resistors, capacitors,
and diodes have been placed into the following
groups to make them easier to locate on the
chassis and Schematic.
1
-
99
100 - 199
200 - 299
FM TUNING UNIT
The FM signal from the antennaisappliedto the
primary of balanced input transformer
FM tuning unit. The secondary of transformer
forms a tuned circuit with trimmer capacitor Cl
and capacitors C2 and ClA (antenna section of
tuning capacitor). The signal selected by this
tuned circuit is coupled through capacitor C3 to
RF amplifier transistor
The signal is amplified by transistor
tuned circuit of
and couples it through capacitor C8 to the base
of mixer transistor Q2. The RF tuned circuit con-
sists of coil L2, trimmer capacitor C6, and capacitors C7 and
itor).
The local oscillator transistor, Q3, operates at a
frequency that is 10.7 mc higher than the received
FM signal. The oscillator frequency is determined by a tuned circuit composed of coil L4,
trimmer capacitor C14, and capacitors Cl3 and
C14A
(oscillator portion of tuning capacitor). The
output signal from this oscillator is coupled
through capacitor
transistor Q2.
A small DC voltage is coupled from the ratio detector circuit through resistor R5 to diode
in the collector circuit of the oscillator. This
DC voltage,
which changes as the tuning is
FM tuner section.
Amplifier section.
Power supply section.
Ql.
Ql.
Ql
selects the desired signal
C6A
(RF portion of tuning capac-
Cl0
to the base of mixer
Tl
in the
The RF
Tl
Dl
changed,
tuned in.
The oscillator frequency is locked-in by the AFC
voltage in the following manner: The capacitance
between the elements of diode Dl changes when
the AFC voltage that is applied to it changes.
This capacitance is connected in series with
capacitor
connected in parallel with part of coil L4. Thus,
when the capacitance of diode Dl is changed by
the AFC voltage, the total capacitance across
coil L4 is changed. This change in the tuned
circuit capacitance changes the frequency of the
oscillator in such a way as to maintain proper
tuning.
The oscillator and the received FM signals are
mixed in transistor Q2 to produce a 10.7 mc IF
(intermediate frequency) signal, that is coupled
through transformer T2 and capacitor C21 to
the first IF amplifier transistor, Q4. The
amplified IF signal from the collector of tran-
sistor Q4 is coupled through transformer T3
to the base of second IF amplifier transistor
Q5. This IF signal is again amplified by tran-
sistor Q5, coupled through transformer T4,
and amplified by transistor
signal is coupled through transformer T5 and
amplified by the fourth IF amplifier transistor
Q7.
A portion of the signal voltage is taken from the
collector of transistor
D2 to produce an AGC (automatic gain control)
voltage, This AGC voltage, which increases and
decreases with the strength of the received FM
signal,
R12 to the base of transistor Q4, where it
automatically controls the gain of the IF signal.
The AGC voltage is then coupledfrom the emitter
of transistor Q4, through resistor
of RF amplifier transistor
ically controls the gain of the FM signal in
the tuner section.
is used as an AFC (automatic fre-
C19.
and these two capacitances are
Q6.
From Q6 the
Q6
and rectified by diode
is coupled through resistors R14 and
RlO,
to the base
Ql.
This automat-
Figure 11
All, or only one of the IF amplifier stages may
operate as limiters. For a very weak signal,
only the fourth IF amplifier
and transistors Q4, Q5, and
Q7
may be limiting,
Q6
would be
amplifying the IF signal. For a very strong
signal, all four IF amplifiers may be acting as
limiters. This limiting action removes
amplitude modulation from the FM signal. Limiting
action is also provided by the self-limiting
characteristics of the ratio detector circuit.
RATIO DETECTOR CIRCUIT
From the collector of transistor Q7, the IF signal
is coupled through resistor R26 and ratio de-
tector transformer T6 to the ratio detector
cir-
cuit. This circuit, which separates the audio sig-
nal from the 10.7 mc IF signal. is shown re-
drawn for greater clarity and simplified in Figure 11. Transformer T6 is represented in this
Ll,
figure by primary coil
ondary composed of coils L2 and L3.
a center tapped sec-
and a
third
or tertiary winding. L4. L4 is just a few turns of
wire
tightly
mary
wrapped around the bottom of pri-
Ll.
NOTE: In the actual circuit, choke L5
and coil L6 are also connected in series with
coil L4, resistor R31, capacitor C39, and resistor R39,
Notice that each diode has its own separate loop
through which its current flows (indicated by the
arrows). Current flowing in diode D3 is controlled by the voltage induced in L2 and L4 which
charges capacitor C33. The current flowing in
diode D4 is controlled by the voltage induced
in coils L3 and L4 which charges capacitor C34.
Current flows through L4 in both directions,
since this coil is common to both current loops,
The two currents flow through capacitors C33
and C34 in the same direction. Electrolytic
capacitor C35 is connected across both of these
capacitors through resistors R27 and R30.
This large capacitor keeps the total voltage
across these two capacitors from changing, thus,
any amplitude changes on the IF signal are
damped out by this capacitor.
The audio output signal from the ratio detector
circuit is applied to the base of Q8. Note that
the two loop currents are flowing in opposite
directions through coil L4, resistor R31, capacitor C39, and the input resistance of Q8. At the
FM IF center frequency of 10.7 mc, the diode
currents are equal, thus they cancel each other
out and no voltage appears across the input resistance of Q8.
Consider a separate voltage to be induced by the
primary into each of the windings, L2, L3, and
L4. L4, which is closely coupled to the primary
introduces a voltage that is in series with both
L2 and L3. This voltage across L4 is relatively
constant in amplitude as long as the voltage
Ll
across
voltage across
does not change. (Remember, the
Ll
will stay relatively constant
due to the limiting action of transistor Q7.)
When the IF frequency deviates from 10.7 mc
due to FM modulation (audio signal), the current
in one diode loop increases while the current in
the other loop decreases. These changes are
caused by a change in phase relationship in the
signal current across coils L2 and L4. and L3
and L4. Now current flows through the input
resistance of Q8 in the direction of the larger
signal, and an output voltage is developed
RIC>HT signal
R
Figure 12
across the input resistance of Q8, The amplitude of this output voltage is determined by
how far the IF frequency deviates from the
center frequency of 10.7 mc. The frequency
of this audio output voltage is determined by
how often the frequency deviates from 10.7 mc.
.-
The slug in the secondary of coil T6 is used to
balance the ratio detector circuit. Capacitor
C36 and L5 removes any remaining 10.7 mc IF
signal from the audio signal. Resistors R28 and
R29 are load resistors for diodes D3 and D4.
FM STEREO MULTIPLEX CIRCUIT
Figures 12A and 12B show two sample signals
that might appear from the left (L) and right
(R) channel microphones of a radio station that
is broadcasting a stereo FM signal, The transmitting circuits then combine these signals to
produce the
L+R
signal shown in Figure 13Aand
the L-R subcarrier signal shown in Figure 13B.
The L-R subcarrier signal is a suppressed
carrier amplitude modulated signal on a 38 kc
subcarrier, and is called the subcarrier channel.
Figure 13
These two signals,
L+R
and L-R, arc then com-
bined with the 19 kc pilot signal shown in Figure
13C. This whole complex signal modulates the
FM carrier and is then radiated from the
broadcasting antenna.
Figure 14 shows the locations of
the different
components that modulate an FM stereo signal.
The “main channel”
15 kc. Monaural
signal is from 50 cps to
FM
tuners use only this part of
the signal, and the remaining parts are atten-
uated by the tuners de-emphasis network,
L+R
AUDIO
MULTIFLEX SIGNAL’
L-R
I
sca signals
lls
TTED
IONS 1
Figure 14
A 19 kc pilot signal is transmitted to give the
proper phasing for the demodulated
channel, The 38 kc
subcarrier
subcarrier
channel is
AM
modulated from 23 kc to 53 kc.
A second subcarrier signal is transmitted by
some stations at 67 kc. This is usually a commercial music signal. This signal is called the
SCA (Subsidiary Communications Authorization)
channel.
The signal that is used for stereo multiplex
operation is coupled from the ratio detector.
through capacitor C39 and the SCA filter, to
audio amplifier transistor Q8. The SCA filter,
which
consists of coil L6 and capacitors
C4O
and C41, removes the 67 kc SCA signal. These
signals are not used for stereo reception.
and main channel signal that comes from tran-
sistor Q9. Waveform
2 is the 38 kc oscillator
signal that is reinserted in the stereo signal at
the same phase and frequency as the original 38
kc carrier. Remember, this 38 kc oscillation
was locked at the correct frequency and phase by
the 19 kc pilot signal from
Q9.
The actual detection process takes place in the
following manner:
When waveform 3 is applied
to the switching detector transistors, Q12 only
conducts
ries the L waveform, Thus, only the
form 4 appears at its output. Transistor
only
on
that part of the waveform that car-
L
wave-
Qll
conducts on the R portion of the 38 kc
waveform, thus only the R waveform 5 appears
at its output. These are the left and right sig-
nals originating at the broadcasting station.
The complete stereo multiplex signal consists of
the
(L+R)
main channel, the (L-R) subchannel,
19
and the
kc pilot signal, The complete stereo
signal is amplified by transistor Q8 andcoupled
through capacitor C43 to
19
kc amplifier transistor Q9. The collector circuit of transistor Q9
is tuned to 19 kc by
coil
L7 and capacitor C44.
Phase control R43 and capacitor C45 are connected across a portion of coil L7 so the phase
of the 19 kc signal can be adjusted, The 19 kc
signal is then coupled to the base of the 38 kc
oscillator transistor,
Q10.
where it locks the
38 kc oscillator in phase and frequency with the
transmitted 38 kc subcarrier signal,
The 38 kc oscillator signal from transistor QIO
is applied through transformer T7 to the base
circuits of switching detector transistors Q11
and Q12. At the same time, the main channel
(L+R) and subchannel (L-R) signals are coupled
from the emitter of transistor Q9 to the emitters
of transistors
Qll
and QI2,
When the main channel and subchannel signals
are combined with the 38 kc oscillator signal in
the switching detector
circuit,
the 38 kc carrier
that was removed at the transmitter (suppressed
carrier transmission) is reinserted into the
stereo signal (waveform 3 on Block Diagram),
in
Figure 16, the 38 kc signal is shown super-
imposed on the stereo signal. At each 38 kc
peak on the L waveform, Q12 conducts and Qll.
is cut off. At each 38 kc peak on the R waveform, $12 is cut off and Qll conducts. The L
signal from transistor $12, charges capacitor
C54: the R signal from transistor
Qll,
charges
capacitor C55.
L WAVEFORM
Q12
CONDUCTS
Q11 cut-off
3
,o
Figure 15 shows the various waveforms that
are present in the switching detector circuit,
Waveform
1
is the suppressed carrier steres
?
WAVEFORM
(Q12 2 CUT-OFF
Cl11 CONDUCT5
F
igure
16
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LEFT
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RIGH r’ WAVEFORM
31 i CONDUCTS
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SWITChcD
DFTFICTIChl
RIGHT WAVEFORM
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LEFT WAVEFORM
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Figure
The left and right channel audio signals then are
applied to individual 38 kc PEC filters that
remove any remaining 38 kc signal. Proper
de-emphasis of each signal is provided by the
combinations of the PEC components and ca-
pacitors C57 and C58, The stereo signals are
then connected to the Left and Right channel
outputs.
When the Phase switch is in the “out” position,
a 38 kc bandpass filter is connected into the
circuit (coil L8 and capacitor C52. This circuit
allows only the
through to transistors
38
kc subcarrier channel
Qll
and Q12. The phase
to pass
control is used to adjust for proper phasing
75
between the reinserted 38 kc carrier and the
38 kc subcarrier signal, This insures maximum separation from the receiver, (The Phase
control is adjusted by listening for maximum
sound in the subcarrier signal: the presence
of main channel sound would make this adjustment impossible.)
A small amount of the 19 kc signal is coupled
from coil L7, through capacitor C38, to the base
of stereo indicator amplifier transistor Q13.
This 19 kc signal is only present when a stereo
signal is being broadcast.
MONOPHONIC FM OPERATION
The monophonic signal is coupled from the ratio
detector circuit to
the
base of transistor Q8.
After amplification, this signal is coupled to
transistor Q9.
follower since no 19
Q9
acts only as an emitter
kc signal is present.
The monophonic signal is then coupled through
capacitor C52 to the emitters of transistor
and Q12. No
transistors Qll and
oscillator
Q12,
signal is coupled to
since the 38 kc oscil-
Q11
lator circuit is disabled by the Source switch.
LEFT CHANNEL AMPLIFIER
The
consists
channel
complete amplifier section of
of
a left
amplifier, The left
channel
amplifier and a right
and
the
Receiver
right amplifiers
are identical; therefore, in order to simplifv
this description, only
the
left channel amplifier
will be discussed,
The
FM
signal from the FM tuner section is
applied through resistor
switch contacts 6 and 3 to
sistor Q1. Resistor
R105 and Source
the
base of
R11
1 1s used to pro-
tran-
vide the proper load impedance for the phono
cartridge. ‘Transistor Ql operates as a high-
gain low-noise amplifier to increase the level
of the incoming signal,
The amplified signal from the collector of Ql
is applied directly to the ‘base of transistor
Q3. Transistor Q3 amplifies the signal again.
DC feedback is applied from the emitter of Q3 to
the base of Ql through resistor R117. From the
collector of Q3, for Phone operation, a portion of
the signal is applied through a frequency selective network. which corisists of capacitors Cl05
and ClO9, resistor
Rl25,
and the Source switch.
This network provides RIAA equalization,
Transistors
Qll
and
Q12
will conduct when no
38 kc signal is applied to their bases. Then the
same monophonic signal is present at the collectors of transistors
Qll
and Q12. These signals
are then coupled through the de-emphasis circuits to the Left and Right channel outputs,
The equalized signal from the collector of Q3
is applied through capacitor Cl07 to Volume
control R129. The amount of signal required to
produce the desired listening level is tapped
off by the slider portion of the Volume control,
This signal voltage is applied through the Bass
and Treble control circuits to the base of
amplifier transistor Q5.
The signal from Cl07 is also applied through iso-
lation resistors R181 and R183 to the Tape Cut-
put jack.
Q5
Transistor
further amplifies the signal.
A small portion of the signal from the collector
of Q5 is applied as feedback through capacitor
Cl17 and part of the tone control network to the
base of Q5. The output signal from the collector of Q5 is coupled through capacitor C119
and resistor R149 to the base of transistor
Q9
Q7. Transistors Q7 and
are direct-coupled
amplifiers which further amplify the signal.
The
of
amplified
Q9
is coupled through capacitor Cl25 to the
base of driver transistor
The amplified signal from the collector of
signal from the collector
Qll.
Qll
is applied to the bases of the output transistors, Q13 and Q15. Diode DlOl determines
the AB operating point of the output transistors,
eliminates crossover distortion, and also provides temperature stability.
Transistors Q13 and Ql5 are connected as a
push-pull output stage. The output signal from
this stage is applied through capacitor
C129 and
the switch contacts on the rear of the Bass
control to the speakers. The output signal is also
applied across a voltage divider network made
up of resistors R173 and R175, The voltage di-
vider applies a portion of the signal through
resistor R151 and capacitor Cl21 as overall
negative feedback to the base of transistor Q7.
If a stereo headphone set is plugged into the
Phone jack, the signal is applied to the headphones. The speaker can be disconnected using
the switch on the Bass control.
POWER SUPPLY
The fused transformer-operated power supply
uses four silicon diodes, 0200 through D203, in
C201
a bridge rectifier circuit. Capacitor
filters
the supply voltage for the power output stages.
Resistor
and capacitor
C202
provide the
R201
supply voltage for the stereo indicator lamp.
An electronic filter, consisting of transistor
QlOO,
resistors R205, R206, and R207, and capacitor
transistors, Q3, Q4, Q5, and
C205,
provide filtering for preamplifier
Q6.
The final
filtering for high-gain low-noise preamplifiers
Q1 and Q2, is accomplished by resistor R208
and capacitor
C207.
The supply voltage for the Tuner section is ob-
R201
tained through resistors
pacitors
C202
and
C203,
and R202. Ca-
provide filtering.
The DC voltage for the pilot lamps is obtained
from the junction of diodes D200 and D202.
Dropping resistor R200 lowers the voltage to
the proper lamp operating voltage. The switched
AC socket and the primary of the power transformer are activated by the On-Off switch. The
unswitched
AC socket is connected directly
across the line and supplies power continuously.
INPUT CONNECTIONS
SPEAKER CONNECTIONS
Shielded cables, terminated in standard phono
plugs, should be used to connect all signal sources
to the input sockets of your Receiver. The
following information gives the correct input
connections for the various types of signal
sources.
Phmo Input
For magnetic or variable reluctance phono
cartridges.
A uxil iary Input
For use with most high level signal sources such
as a television receiver or tape recorders with
preamplifier output. A record changer or a turn-
table
eqtipped
with a crystal or ceramic stereo
cartridge may also be connected to the AUX
INPUTS. However, the BASS control should be
turned up in order to compensate for the low
freqtency
losses when using these cartridges.
Ground Terminal
In some cases the mechanism of a
turiitable
or
a changer is not connected to the audio cable
shield, To reduce hum in these cases. a separate
ground wire should be connected from the turn-
table to this ground terminal.
(
) If your left
”
or C, connect a wire from this lug to
mon.
speaker has a lug marked “corn
the COM (common) connecting screw of the
LEFT SPEAKER output terminal, If your left
speaker lugs are not marked, connect a wire
from either of these lugs to the LEFT
SPEAKER output term
inal.
( ) Connect the other left speaker wire to the
other LEFT SPEAKER connecting screw.
(
)
If
your right
“common,
speaker has a lug marked
”
or C, connect a wire from this
lug to the COM (common) connecting screw
of the RIGHT SPEAKER output terminal. If
your right speaker lugs are not marked,
connect a wire from either of these lugs to
the RIGHT SPEAKER output terminal.
( )
Connect the other
right
speaker wire to the
other RIGHT SPEAKER connecting screw.
Speaker Phasing
NOTE: If the
“conmon”
lugs of your left and right
speakers were marked, this phasing procedure
can be
disregarded:
the connections made in the
preceding; steps provided proper phasing for your
speakers.
-
TAPE OUTPUT
When connecting this Amplifier to a tape recorder, the high level input of the recorder
should be used, This input is sometimes called
High Level, Radio,
or Line Input. AT NO TIME
SHOULD A TAPE RECORDER BE CONNECTED
TO THE AMPLIFIERSPEAKERCONNECTIONS,
as serious damage could result to the Receiver.
AC OUTLETS
Switched AC Outlet
For supplying power to devices such as record
changers, which may then be controlled by the
On-
Off switch on the Amplifier.
Normal AC Outlet
For supplying power to devices such as record
changers or tape decks. which may be damaged if
power is removed without turning off the mechan-
ism.
The two speakers should be connected so that
they are
“in-phase.” “In-phase” means that
both speaker cones move in the same direction at
the same time. when driven by identical
signals.
If multiple-speaker systems are used, phasing
refers to the
low-frequency
speaker in each
system.)
Speaker phasing can be determined easily in the
following manner: Disconnect both phono input
cables, and set the SOURCE switch to the
PHONO
@
input. Introduce a hum in both chan-
nels by inserting a length of bare wire or a
screwdriver in one of the empty input sockets:
then advance the VCLUME controls until a hum
is heard.
Place the speakers side by side, Note the loudness of the hum when you stand directly in front
of and between the speakers. Now interchange the
two speaker wires
on
one channel. When the
loudest hum is heard the speakers are in phase.
Speaker Placement INDOOR ANTEKNAS
Generally, for stereo
listeninq,
the two speakers
should be spaced four to eight feet apart. They
should be placed along a wall either
facirg
straight ahead or “firing in” slightly toward each
other’s axis. The optimum
positiors
can best be
determined by experiment. A great deal depends
upon the size and acoustics of the room and
upon
the high frequency dispersion characteristics
of the speakers. Identical speakers or speaker
systems are recommended.
spac
ing
also
Correct speaker
extent upon the
from the speaker
listener’
s
s, In othe
depmds
positiori and
r words,if the
ing position is restricted to one that is
tively
close to the speakers, some improvement
to some
distant
listen-
rela-
could probably be obtained by moving the speak-
ers closer together.
Remember that stereophonic reproductim is
striving to recreate, as accurately in position as
possible, not
onlv
the sounds that originate at
the “right” or left", but also those near the
center. Best results will be obtained if vou
L
experiment with speaker and listening positions:
this will help you arrive at the best set of con-
ditions for your installation,
L
e
to
with
~obtaintx!
from the
statims
this ant emat, Weakest
thOS e
that
that are broadside
recqtion
will occur
ant ema.
Stereo Headphone Jack
A set of stereo headphones can be plugged
directly into this jack. The external speakers
are disconnected when the switch
on the BASS
control is pulled out, Program material can be
tape recorded
of the tape
bv plugging the high level input
recor-der into this jack.
Figure 8 shows a type of plug that can be installed
on the end of a stereo headphone or tape recorder
cable. The
t
ip of the plug connects to the right
channel of the jack.
LEFT CHANNEL
ChAN
RIGHT
SIGNAL
WIRE
AND
CHANNEL
RIGHT
LEFT
COMMON WIRES
Figure 8
Figure 9
OUTROOR ANTENNAS
To receive weaker stations, or in weak signal
areas,
an outdoor antenna will be necessary.
BEST RECEPTION FOR STEREO FM WILL
OCCUR WITH A COMMERCIAL FM
CUTDOOR
ANTENNA. A VHF TV antenna can also be
used as an FM antenna, since FM stations are
actually located between TV channels 6 and
c
Do not connect a TV antenna to both the TV set
and the Receiver at the
same time, unless a
TV antenna coupler is used, or a weak and dis-
torted signal
mav occur in both
couplers are not.’ recommended because
amounts of signal
amplifier type of coupler
is no loss of signal
a-re
lost iii them, Use a pre-
ins
.
ullits,
Pad tvpe
.
large
toad, where there
3,
SOURCE SWITCH
NOTE: This is a three wafer switch: it allows
the inputs
mu1t
aneously.
of
both channels to be selected
It
also
turns the
38 kc oscillator
si-
off when inputs other then stereo FM are used,
VOLUME
The dual-concentric clutched VOLUME control
allows the listening level of each channel to be
adjusted simultaneously or individually, Max-
imum volume is obtained when the knobs are
rotated fully clockwise.
BASS CONTROL AND SPEAKER ON-OFF
SWITCH
of
When the SOURCE switch is in one
phonic
M
ositions.
P
the input signals from
the mono-
both the left and right channels will be combined and heard in both the left and right speak-
ers, In the stereo
the left Channel Inputs will
left speaker,
S
positions, all signals from
be
heard
and all Right Channel
only
signals
in the
will
be heard only in the right speaker,
In the m onophoni(:
M
FM position, the same
signal is present at the Left and Right output
sockets.
In the stereo
S
FM position (when
tuned to a station that is broadcasting stereo),
channel signal is
one
and the other channel
heard
in the left speaker
signal
is heard in the right
speaker,
NOTE: The
FM pssition should
only
be used
S
when a station is broadcasting stereo; otherwise, subchannel noise may be heard on regular
FM
programs.
Also, noise may be heard from
c
stations that broadcast a Subsidiary Communications Authorization SCA
signal.
The BASS control is of dual-tandem construction.
The low frequency response is simultaneouslv
varied by the samk amount in both channels,
Flat
response is obtained when the knob is at approximately 12 o’clock, Clockwise rotation produces
boost, and counterclockwise rotation produces
cut of the low frequencies. Pulling the control
knob out, disconnects the speakers and allows
private listening with headphones.
TREBLE CONTROL AND POWER ON-OFF
SWITCH
The TREBLE control is of dual-tandem construction, The total response is simultaneously
varied by the same amount in both channels.
Flat response is obtained when the knob is at
approximately 12 o’clock. Clockwise rotation
produces boost, and counterclockwise rotation
produces cut of the high frequencies.
The On-Off switch is located on the TREBLE
control, Pull the TREBLE control knob out to
turn the Receiver ON, and push the knob in to
turn it OFF.
Figure 10
TUNING
This control changes the dial setting and tunes
in the desired station.
STEREO INDICATOR LAMP
This indicator will light with a steady glow
a,
when an FM station that is broadcasting a
stereo signal is tuned in. if the SOURCE switch
@)
is in the
FM, @ FM; @ AUX, or @ AUX
positions. Note that in some cases it may flicker
on
and off due to the noise between stations,
It may also light for short periods of time on
stations that use a “Commercial Killer” signal.
This
signal eliminates the commercials from
the music that these stations sell to business
establishments.
HOW TO GET THE MOST OUT OF YOUR
RECEIVER
Use the following procedure to get the greatest
possible enjoyment out of this high quality Stereo
Receiver, The Receiver should be connected to
good quality speakers.
The speakers should be
placed far enough apart to provide good stereo
separation: approximately 4 to 8 feet.
Set the SOURCE switch to the @ FM position,
Tune in a station that is broadcasting stereo,
as indicated by a steady glow of the stereo
indicator lamp.
Pull out the PHASE control knob and adjust this
control in either direction for the loudest output.
Then push the knob back in without disturbing
the setting of this control.
PHASE CONTROL AND SWITCH
This control and switch is only used when tuned
to a station that is broadcasting an FM stereo
signal. The SOURCE switch must be set at the
@
FM position. When you tune to different
stations, the Phase control will produce maximum stereo separation by correcting any transmitted phase errors.
To set the PHASE control, pull the knob out to
activate the switch, and adjust the control in
either direction for the loudest output signal.
Then push the knob back in without disturbing
the control setting,
NOTE: The Phase control adjusts the phase of
the 38 kc reinserted carrier. It may be
neces-
c
sary to readjust this control when tuning to
another station, to correct transmitted phase
errors and obtain maximum stereo separation.
@
Set the SOURCE switch to the
FM position.
Adjust the volume controls to produce an equal
sound levelfromeach speaker at the desired
listening level.
To receive monophonic FM programs, always
@
set the SOURCE switch to the
tion.
This will produce the best
FM posi-
signal-to-
noise ratio,
ALIGNMENT WITH INSTRUMENTS
This alignment procedure requires the use of
test equipment. It should only be performed
those who
have
instrument alignment exper
bv
ience.
IF ALIGNMENT
Equipment
needed: A high impedance input DC
VTVM, and an RF generator that is accurate at
10.7 mc, A
FM0-1
kit
alents, may be used,
Heathkit
Test Oscillator, or their equiv-
VTVM and the Heath-
I
IF ALIGNMENT CHART
GENERATOR
PREPARATION
Connect a jumper
wire between
points X and Y
on the FMMultiplex
circuit board.
Remove jumper
wire from between
points X and Y.
Connect
To
Antenna
~ input
terminals.
Antenna
input
terminals.
Frequency
And
output
10. 7 mc (without
modulation). Set
generator output
for 2 volts on
VTVM.
10.
7
mc (without
modulation). Re
duce generator
output to maintain
2 volts on VTVM.
10. 7 mc without
modulation.
”
( ) Set the Receiver controls as follows:
-
SOURCE switch to @ FM.
PHASE switch pushed in.
TUNING to low frequency end of dial,
Refer to Figures 4 and 5 (fold-out from Page
65) for coil, transformer, and TP (test point)
locations.
Complete the adjustments given in
the Alignment Chart below.
-GGJ-
Connect
To
Transformer
I
I
I
Bottom slug
of T6
AOJUS
For VTVM
Reading
I
TPl
I
1
T
Top and bottom
slugs of T5
I
Top and bottom
slugs of T4
TPl
TP2
TP2
I
Top and bottom
slugs of T3
Top and bottom
slugs of T2
t-
t
Repeat each step
above until no
further improve-
ment is obtained.
1
1
Top slug of
T6
If necessary,
readjust top
slug of T6.
Maximum
reading.
Zero
reading.
FRONT END ALIGNMENT
Equipment needed: An RF generator and a high
input impedance DC VTVM.
Complete the steps in the following Alignment
Chart.
FRONT END ALIGNMENT CHART
RECEIVER
VTVM READING
To maximum
Cl and C6
STEREO ALIGNMENT
Equipment needed:
VTVM. The
Heathkit
Audio generator and
Models IG-72 or IG-82
&4C
Audio Generators and the Model IM-21 AC
VTVM, or their equivalents may be used.
( ) Disconnect the negative lead of capacitor
C39
from the circuit board at point
See Figures 4 and 5 (fold-out from Page
R,
65),
Complete the steps in the Stereo Alignment Chart
and the
steps that follow the chart.
STEREO ALIGNMENT CHART
AUDIO GENERATOR
AND
switch
PHASE switch
pulled out.
Push PHASE
switch in.
Adjust
PHASE con-
trol to about
2 o’clock
position.
to M
FM.
Connect To
Negative
(-) lead
of
capac-
itor C39.
Frequency
38 kc (~200 cps)
. 01 volt rms
output.
67
rms output.
And
output
kc .l volt
VTVM
Connect To
TP3
Coil
L8
L6
ADJUST
For VTVM
Reading
Maximum
reading (about
.2 volt rms).
Minimum
reading (about
.
.007 volt rms).
( )
Disconnect the AC VTVM and the audio gen-
erator from the Receiver.
>
Reconnect the negative (-) lead of capacitor
(
C39
to the circuit board at point R and
solder the connection.
NOTE:
To obtain the most accurate alignment,
coil L7 and transformer T7 should be adjusted
by using an FM stereo broadcast signal, rather
than by using instruments.
( ) Adjust coil L7 and transformer T7
bycom-
pleting the steps under FM Stereo Adjust-
ments on Page 48.
This completes the Stereo Alignment,
CHANNEL SEPARATION TESTS
3.Turn the slug clockwise
l/4
turn.
If an FM stereo generator is available, this
generator may be used to check channel separa-
tion. To check separation, coil
er T7 must be adjusted as outlined in the following steps.
Equipment needed: FM stereo generator and AC
VTVM. If desired, an oscilloscope may also be
used.
Disconnect the negative (-) lead of capacitor
C39 from the circuit board at point
Connect the
lead to the negative
c39.
( ) Connect the AC VTVM (and oscilloscope if
desired) to the RIGHT TAPE OUTPUT
socket of the Receiver.
)
Set the SOURCE switch on the Receiver to
(
the
S
FM position.
) Set the FM stereo generator to the right
channel output and use the 19 kc pilot signal
with a 1 kc multiplex signal.
FM
stereo generator output
L7 and transform-
(-)
lead of capacitor
R,
Readjust coil L7 until a null or minimum
( >
sound output is obtained. NOTE: If there
are two nulls, use the null adjustment that
is closer to the top of the coil. The proper
adjustment should be close to the point of
maximum brightness of the stereo indicator
lamp.
Turn the PHASE control counterclockw
>
for a maximum output reading, then push
PHASE switch in.
( ) Note the output reading on the VTVM. Then
change the FM stereo generator to the left
channel output and note the VTVM output
reading for this position. The difference
between the two output readings is the right
channel separation,
db (decibels).
Disconnect the VTVM (and oscilloscope if
( >
used) from the RIGHT TAPE OUTPUT
socket and connect it to the LEFT TAPE
OUTPUT socket of the Receiver.
usually expressed in
ise
the
)
Adjust coil L7 for maximum brilliance of
the stereo indicator lamp.
( ) Pull out the PHASE switch,
PHASE control fully clockwise.
NOTE: Complete the following adjustments very
carefully to obtain good stereo listening.
(
)
Adjust transformer T7 as follows:
Turn the slug (not more than one turn
1.
in either direction) until the
put is clear,
2
Turn the slug counterclockwise to the
.
point where the sound output just starts
to become garbled, Note the position
of the flag on the alignment tool.
then adjust
the
sound out-
Turn the channel switch of the FM stereo
( )
generator to the right channel position, then
to the left channel position, Note the output
reading on the VTVM for each position. The
left channel separation is the difference between these two readings.
Disconnect the FM stereo generator,
( 1
VTVM, and oscilloscope (if used) from the
Receiver.
Reconnect the negative lead of capacitor
( >
C39 to the circuit board at point R; then
resolder the connection.
This completes the Channel Separation
AC
Tests.
FM SECTION
SPECIFICATIONS
Tuning Range.
. . 0 0 0 0 .00
Antenna Input Impedance.
Sensitivity, .
0.00..
Intermediate Frequency (IF). .
Hum And Noise.
..o.ooooooooooooooooo
. .
l ~oooooo
0 0 0 0 0 0 0
. . . . .
. .
0 0
l
0.00..
0.00..
. . . . .
0.00..
0 0 0 0 0
Audio Frequency Response. . . . . . . . . . . . . . .
Harmonic Distortion. . . . . . . . . . . . . . . . . .
Image Ratio.
Capture Ratio.
l oooooooo
0.00..
l oooooo
0 0 0 0
0.00..
0 0 0 0 0 0 0 0 0
0 0 0 0
AFC Correction. . . . . . . . . . . . . . . . . . . . .
AM Suppression. . . . . . . . . . . . . . . . . . . . .
IF Rejection. . . . . . . . .
Separation. .
0 0 0 0 0 0 0
l . . . . . . . . . . . . . .
0 0 0 0 0 0 0
0 0 0 00 0 0 0
88-108 mc,
0, balanced input.
300
5 microvolts,*
10.7 mc,
-50 db, 1 watt reference.
Monophonic :
1%
or less.*
-45
db,*
3
db,*
150 kc per volt.
-35
db,*
-80
db,*
30 db at 1000 cps.
0
0 to -3 db from 20 to 15,000 cps.
AMPLIFIER SECTION
000
Continuous Power Output.
Music Power Output. .
0 0
Speaker Output Impedance.
Tape Output Impedance. .
.. 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 000
.
0 0 0 0 0 0 0 0 0
0 0 0
l ooooooo00
0 0 0
Damping Factor, . l ooooooooooooeooo..
Hum And Noise,. . . . . . . . . . . . .
*Rated
IHF
(Institute of High Fidelity) Standards.
8..
. . . . .
10 watts per
0
15 watts per
4 through 16
0
3500
50 or higher.
Phono:
Auxiliary: -63 db; input shorted.
channel.
channel.*
0.
cl.
-60 db; 10 MV reference-input shorted.
5
4
3
2
1
Q1
300 ^
ANTENNA
CONNECTOR
D D
1
T1
C1A
C1
C3
5.6pf
C2
6.8pf
2
C C
2SA240
RF AMPLIFIER
R1
470
C8
2.5pf
L2
C6A
C6
C9
.02mf
C7
15pf
R3
10K
L3
R2
2.7K
Q2
2SA240
MIXER
C10
1.5pf
C12
120pf
C11
.02mf
R4
1K
T2
AGC
IF a
Z
IF b
Y
AGC
T
+8V
+8 V
S
C5
.02mf
L4
B B
C13
12pf
C14
C14A
LOCAL OSCILLATOR
Q3
2SA239
C17
10pf
C16
10pf
C19
15pf
D1
R5
10K
C21
.02mf
AFC
C20
.02mf
AFG
X
U
R8
R7
2.7K
1.2K
A A
C15
.02mf
R6
4.7K
C18
.02mf
Heathkit FM Radio AR-14
5
4
3
2
1
5
4
3
R204
270 1W
2
D +28.6V
1
D
+ C204
Q100
R205
6.8K
2N2712
R206
47K
R207
820
+ C205
100mf
D D
POWER SUPPLY
PILOT LIGHT
LAMP 47
R200
75 5W
100mf
R208
1.5K
+ C206
100mf
E
F
+ C207
100mf
E +28V
F +26.8V
G
C C
POWER SWITCH ON
TREBLE CONTROL
1 2
F1
1 Amp Slow Blow
120 VOLT WIRING
T8
BLK
1
A +38V
A
B +17V
B
120V
AC AC SOCKET
BLK-YEL
BLK-GRN
PLUG
BLK-RED
C200
B B
POWER SWITCH
ON TREBLE CONTROL
1 2
P1
.01 MF
1600 V
F1
1/2 Amp Slow Blow
BLK
BLK-YEL
BLK-GRN
A A
PLUG
BLK-RED
C200
.01 MF
2
3
4
240 VOLT WIRING
T8
1
2
3
4
1600 V
D1
- +
R201
330 5W
+ C201
4000mf
R202
150 1W
+ C202
500mf
+ C203
500mf
R203
220 1W
C +8V
C
5
4
3
2
1
5
4
3
2
1
C21
D D
150pf
IF a
R53
C22
470pf
47K
IF b
R10
3.3k
1ST IF AMPLIFIER 2ND IF AMPLIFIER 3RD IF AMPLIFIER
Q4
2N2654
R12
3.3k
T3
R18
Q5
2N2654
270
T4
Q6
2N2654
R22
270
C30
6.8pf
AGC
R16
1.5K
R17
1.5K
C27
.01MF
C C
C +8 VOLTS
R9
33
R11
33
R13
1.5K
C25
.01mf
R15
5.6K
C26
.01MF
C28
.01MF
R19
5.6K
R20
1.5K
C29
.01MF
R21
1K
D2
+8 V
R14
AGC
C23
.01MF
+ C24
10MF
10K
RATIO DETECTOR CIRCUIT
R27 1K
B B
R32
1 MEG
T1
R28
6.8K
R29
6.8K
C35
+
5MF
L6
TO STEREO MULTIPLEXER
Q8
R31
150
IF FM
L5
90 uH
C33
270pf
C34
270pf
R30
1.5K
+
T5
R24
C31
A A
R23
5.6K
.01MF
1.2K
4TH IF AMPLIFIER
Q7
2N2654
C32
.01MF
R25
1K
R26
470
AFG
C37
.01MF
5
4
C36
270PF
C39
10mf
3
C40
400pf
2
C41
680pf
1
5
4
3
2
1
AUDIO AMPLIFIER
C56
10MF
+
B +17V
LAMP
STEREO
INDICATOR
3
R51
220K
REAR OF
WAFER #3
STEREO LEFT
C +8V
Q13
C45
390pf
2N2712
R35
120K
1K
R36
D D
68K
Q8
C41
680pf
C C
R39
10K
R37
2.2K
Q8
2N2712
R40
220
C43
10MF
+
C42
.01MF
R38
47K
EMITTER FOLLOWER
R41
47K
19 KC 6
AMPLIFIER AND
Q9
2N2712
5
L7
4
2 R34
C38
200pf
C44
.01MF
R43
10K
1
R42
560
PHASE
R33
33
Q14
2N2712
R.E.C.
31
Q11
38KC
OSCILLATOR
R45
Q10
39K
B B
R44
560
C46
.01MF
2N2712
C49
2700pf
1
2
C50
.01MF
T7
R48
15K
5
C51
.01MF
R50
10K
2N2712
C55
.001MF
2
C57
.002MF
6
R49
47K
Q12
2N2712
C54
.001MF
C58
.002MF
2
31
C59
10MF
+
R52
220K
4
STEREO RIGHT
C47
.01MF
R46
6.8K
R47
2.2K
C48
.2MF
3
4 7
ON PHASE
ADJUST CONTROL
ADJ
NORMAL
A A
C52
10MF
C53
R.E.C.
+
L8
470pf
5
4
3
2
1
5
R108
4.7K
12
R107
4.7K
11
FRONT-OF
WAFER-#2
8
10
R110
4.7K
7
9
R109
4.7K
R102
PHONO
RIGHT
D D
AUX
RIGHT
FM
RIGHT
C C
STEREO RIGHT
PHONO
LEFT
B B
AUX
LEFT
FM
LEFT
STEREO LEFT
A A
5
1K
2
R104
180K
4
R106
180K
6
R101
1K
1
R103
180K
3
R105
180K
5
4
REAR-OF
WAFER-#2
8 9
8
10 9
10
12 9
12
2 3
2
10 3
4
10 3
6
4
R179
1K
FRONT OF
3
WAFER #1
CLOSE FOR MONO
OPEN FOR STEREO
9
R180
1K
3
F +26.8V E +28V
R113
56K
Q1
2N3391
C101
10MF
R111
56K
C102
10MF
R112
R56K
+
+
Q2
2N3391
13
14
3
R117
390K
R115
390
15
PHONO
AUX
FM
F +26.8V E +28V
R114
56K
R118
390K
R116
390
16
PHONO
11 10
AUX
11 2
FM
11 12
Q3
2N2712
C103
+
100MF
REAR OF
WAFER #1
5 4
5 6
5 8
Q4
2N2712
C108
+
100MF
REAR OF
WAFER #1
2
R119
10K
R121
100
R125
R123
47K
820
R122
10K
R124
100 C105
R126
R120
820
47K
2
17
18
C107
10MF
+
C105
.0068MF
C109
.0022MF
C110
10MF
+
.0068MF
C106
.0022MF
R127
39K
R128
39K
19
20
R181
2.2K
23
21
R182
2.2K
24
22
1
R129
10K
R130
10K
1
TAPE OUTPUT
27
R183
15K
AF LEFT
TAPE OUTPUT
28
R184
15K
AF RIGHT
5
LEFT CHANNEL
AUTIO AMPLIFIER
R131
D D
5.6K
C111
.047MF
R133 50K
29
31
R135
5.6K
C C
R137
5.6K
25
35
4
33
C113
10MF
C115
.002MF
+
R139
39K
R143
5.6K
3
2
E +28V D +28.6V
R145
C117
10MF
6.8K
+
R147
100K
C119
2MF
+
Q5
2N2712
C121
10pf
R149
6.8k
R151
100K
R153
33K
A +38VA +38V
R165
A
150 1W
R167
150 1W
Q13
TA2577A
Q7
2N2712
R155
100K
R173
560
R157
1K 1/2 W
Q9
2N3416
R175
560
R159
100
C125
500MF
+
C131
.005MF
1
43
AF LEFT
R141
50K
B B
37
C127
500MF
+
D101
1N3754
R185
10
45
R169
1^ 2W
C129
2500MF
+
47
C131
.1MF
LEFT CHANNEL
SPEAKER OUT
4 THROUGH 16 OHMS
S1
C123
.003MF
R161
2.2K
39
Q11
2N3053
R171
1^ 2W
41
A A
5
4
3
R163
91 1/2 W
Q15
2N2148
2
R177
100 1/2 W
J4
1
2
3
PHONEJACK STEREO
1
5
RIGHT CHANNEL
AUTIO AMPLIFIER
R132
D D
5.6K
C112
.047MF
R134 50K
30 34
32
R136
5.6K
C C
R138
5.6K
26
36
4
C114
10MF
+
C116
.002MF
R140
39K
R144
5.6K
C118
10MF
3
2
1
D +28.6VE +28V
R146
6.8K
+
R148
100K
C120
2MF
+
Q6
2N2712
C122
10pf
R150
6.8k
R152
100K
R154
33K
Q8
2N2712
R156
100K
R158
1K 1/2 W
Q10
2N3416
R176
560
R159
100
C126
500MF
+
C132
.005MF
A +38VA +38V
R166
A
150 1W
R168
150 1W
Q14
TA2577A
R174
560
44
AF RIGHT
50K
B B
38
C128
500MF
+
D102
1N3754
R186
10R142
46
R170
1^ 2W
C130
2500MF
+
48
C132
.1MF
RIGHT CHANNEL
SPEAKER OUT
4 THROUGH 16 OHMS
S1
C124
.003MF
R162
2.2K
40
Q12
2N3053
R172
1^ 2W
42
A A
5
4
3
R164
91 1/2 W
Q16
2N2148
2
R178
100 1/2 W
J4
1
2
3
PHONEJACK STEREO
1
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