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CIRCUIT
DESCRIPTION
Each major section of the Receiver will be
changed,
is used as an AFC (automatic fre-
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.
tuned in.
Follow the circuit on the Block Diagram (fold-
out from Page 66) and on the Schematic (fold-
out 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 tuner section.
Amplifier section.
Power supply section.
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 C19. and these two capacitances are
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.
FM TUNING UNIT
The FM signal from the antennaisappliedto the
primary of balanced input transformer Tl in the
FM tuning unit. The secondary of transformer Tl
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 Ql.
The signal is amplified by transistor Ql. The RF
tuned circuit of Ql selects the desired signal
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 ca-
pacitors C7 and C6A (RF portion of tuning capac-
itor).
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 Q6. From Q6 the
signal is coupled through transformer T5 and
amplified by the fourth IF amplifier transistor
Q7.
The local oscillator transistor, Q3, operates at a
frequency that is 10.7 mc higher than the received
FM signal. The oscillator frequency is de-
termined 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 Cl0 to the base of mixer
transistor Q2.
A portion of the signal voltage is taken from the
collector of transistor Q6 and rectified by diode
D2 to produce an AGC (automatic gain control)
voltage, This AGC voltage, which increases and
decreases with the strength of the received FM
signal,
is coupled through resistors R14 and
R12 to the base of transistor Q4, where it
automatically controls the gain of the IF signal.
A small DC voltage is coupled from the ratio de-
tector circuit through resistor R5 to diode Dl
in the collector circuit of the oscillator. This
DC voltage,
which changes as the tuning is
The AGC voltage is then coupledfrom the emitter
of transistor Q4, through resistor RlO, to the base
of RF amplifier transistor Ql. This automat-
ically controls the gain of the FM signal in
the tuner section.
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 Q7 may be limiting,
and transistors Q4, Q5, and 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 ampli-
tude 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 Fig-
ure 11. Transformer T6 is represented in this
figure by primary coil Ll, a center tapped sec-
ondary composed of coils L2 and L3. and a third
or tertiary winding. L4. L4 is just a few turns of
wire tightly wrapped around the bottom of pri-
mary Ll. NOTE: In the actual circuit, choke L5
and coil L6 are also connected in series with
coil L4, resistor R31, capacitor C39, and re-
sistor
R39,
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
across Ll does not change. (Remember, the
voltage across Ll will stay relatively constant
due to the limiting action of transistor Q7.)
Notice that each diode has its own separate loop
through which its current flows (indicated by the
arrows). Current flowing in diode D3 is con-
trolled 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, capac-
itor 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 re-
sistance of Q8.
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 ampli-
tude 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 trans-
mitting 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” signal is from 50 cps to
15 kc. Monaural FM tuners use only this part of
the signal, and the remaining parts are atten-
uated by the tuners de-emphasis network,
L + R
I
L - R
A U D I O
M U L T I F L E X
S I G N A L ’
sca signals
Figure 14
lls
T T E D
I O N S 1
A 19 kc pilot signal is transmitted to give the
proper phasing for the demodulated subcarrier
channel, The 38 kc 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 com-
mercial 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
s i g n a l s a r e n o t u s e d f o r s t e r e o r e c e p t i o n .
The complete stereo multiplex signal consists of
the (L+R) main channel, the (L-R) subchannel,
and the 19 kc pilot signal, The complete stereo
signal is amplified by transistor Q8 andcoupled
through capacitor C43 to 19 kc amplifier tran-
sistor 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 con-
nected 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),
Figure 15 shows the various waveforms that
are present in the switching detector circuit,
Waveform 1 is the suppressed carrier steres
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 on that part of the waveform that car-
ries the L waveform, Thus, only the L wave-
form 4 appears at its output. Transistor Qll
only 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.
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 wave-
form, $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
W A V E F O R M
Q12
C O N D U C T S
Q11 c u t - o f f
,o
3
? W A V E F O R M
(Q12 2 C U T - O F F
Cl11 C O N D U C T 5
F igure
16
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RIGH r’ W A V E F O R M
31
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CONDUCTS
C N L Y O h T H E S E
38 K C P E A K S
I
R I G H T W A V E F O R M
I
Figure 75
between the reinserted 38 kc carrier and the
38 kc subcarrier signal, This insures maxi-
mum 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 adjust-
ment
impossible.)
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 38 kc subcarrier channel to pass
through to transistors Qll and Q12. The phase
control is used to adjust for proper phasing
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. Q9 acts only as an emitter
follower since no 19 kc signal is present.
The monophonic signal is then coupled through
capacitor C52 to the emitters of transistor Q11
and Q12. No oscillator signal is coupled to
transistors Qll and Q12, since the 38 kc oscil-
lator circuit is disabled by the Source switch.
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 col-
lectors of transistors Qll and Q12. These signals
are then coupled through the de-emphasis cir-
cuits to the Left and Right channel outputs,
LEFT CHANNEL AMPLIFIER
The
complete amplifier section of the Receiver
consists of a left channel amplifier and a right
channel
amplifier, The left and 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
R105
and
Source
switch contacts 6 and 3 t o the base of tran-
sistor Q1.
R e s i s t o r R11 1 1s u s e d to p r o -
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
i s 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 selec-
tive network. which corisists of capacitors Cl05
and ClO9, resistor Rl25, and the Source switch.
This network provides RIAA equalization,
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.
Transistor
Q5 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 col-
lector of Q5 is coupled through capacitor C119
and resistor R149 to the base of transistor
Q7. Transistors Q7 and Q9 are direct-coupled
amplifiers which further amplify the signal.
The
amplified
signal from the collector
of Q9 is coupled through capacitor Cl25 to the
base of driver transistor Qll.
The amplified signal from the collector of Qll
is applied to the bases of the output tran-
sistors, Q13 and Q15. Diode DlOl determines
the AB operating point of the output transistors,
eliminates crossover distortion, and also pro-
vides 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 head-
phones. 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
a bridge rectifier circuit. Capacitor C201 filters
the supply voltage for the power output stages.
Resistor R201 and capacitor C202 provide the
supply voltage for the stereo indicator lamp.
An electronic filter, consisting of transistor
QlOO, resistors R205, R206, and R207, and ca-
pacitor C205, provide filtering for preamplifier
transistors,
Q3, Q4, Q5, and 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-
tained through resistors R201 and R202. Ca-
pacitors C202 and C203, 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 trans-
former are activated by the On-Off switch. The
unswitched
AC socket is connected directly
across the line and supplies power contin-
uously.
INPUT
CONNECTIONS
SPEAKER
CONNECTIONS
Shielded cables, terminated in standard phono
plugs, should be used to connect all signal sources
t o t h e i n p u t s o c k e t s o f y o u r R e c e i v e r . T h e
following information gives the correct input
c o n n e c t i o n s f o r t h e v a r i o u s t y p e s o f s i g n a l
sources.
Phmo Input
F o r m a g n e t i c o r v a r i a b l e r e l u c t a n c e p h o n o
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.
TAPE OUTPUT
When connecting this Amplifier to a tape re-
corder,
t h e h i g h l e v e l i n p u t o f t h e r e c o r d e r
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.
( ) If your left speaker has a lug marked “corn -
mon. ” or C, connect a wire from this lug to
the COM (common) connecting screw of the
LEFT SPEAKER output terminal, If your left
speaker lugs are not marked, connect a wire
f r o m e i t h e r o f t h e s e l u g s t o t h e L E F T
SPEAKER output term inal.
(
) Connect the other left speaker wire to the
o t h e r L E F T S P E A K E R c o n n e c t i n g s c r e w .
( ) I f
your
right s p e a k e r h a s a l u g m a r k e d
“common, ” or C, connect a wire from this
lug to the COM (common) connecting screw
of the RIGHT SPEAKER output terminal. If
y o u r r i g h t s p e a k e r l u g s a r e n o t m a r k e d ,
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.
The two speakers should be connected so that
t h e y a r e
“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
r e f e r s t o t h e low-frequency s p e a k e r i n e a c h
system.)
Speaker phasing can be determined easily in the
following manner: Disconnect both phono input
cables,
a n d s e t the S O U R C E s w i t c h t o t h e
PHONO @ input. Introduce a hum in both chan-
n e l s b y i n s e r t i n g a l e n g t h o f b a r e w i r e o r 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 loud-
ness 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.
Correct speaker
extent upon the
from the speaker
spac ing
listener’ s
s, In othe
also depmds to some
positiori
and distant e
r words,if the listen-
ing position is restricted to one that is rela-
tively close to the speakers, some improvement
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
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 bv plugging
the high level input
of the tape 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.
L E F T
C H A N N E L
R I G H T ChAN
SIGNAL
W I R E
L E F T AND R I G H T
C H A N N E L
C O M M O N
W I R E S
Figure 8
~obtaintx! from
the statims that are broadside
to
this ant emat,
Weakest recqtion will occur
with
thOS e
that
ant ema.
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 3,
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 ullits, Pad tvpe
couplers
are
not.’
recommended
because
.
large
amounts of signal a-re lost iii them, Use a pre-
amplifier type of coupler ins toad, where there
is no loss of signal .
SOURCE SWITCH
NOTE: This is a three wafer switch: it allows
the inputs of both channels to be selected si-
mu1t aneously.
It also turns the 38 kc oscillator
off when inputs other then stereo FM are used,
When the SOURCE switch is in one of the mono-
phonic
M P ositions.
the input signals from
both the left and right channels will be com-
bined and heard in both the left and right speak-
ers, In the stereo S positions, all signals from
the left Channel Inputs will b e heard only in the
left speaker, and all Right Channel signals 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),
one channel signal is heard in the left speaker
and the other channel signal is heard in the right
speaker,
NOTE: The S FM pssition should o n l y be used
when a station is broadcasting stereo; other-
wise, subchannel noise may be heard on regular
FM programs.
Also, noise may
be heard from
c
stations that broadcast a Subsidiary Communi-
cations Authorization S C A signal.
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
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 approxi-
mately 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 con-
struction, 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
HOW TO GET THE MOST OUT OF YOUR
RECEIVER
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.
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 maxi-
mum stereo separation by correcting any trans-
mitted 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,
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.
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 @ FM posi-
tion.
This will produce the best signal-to-
noise ratio,
ALIGNMENT WITH INSTRUMENTS
This alignment procedure requires the use of
test equipment. It should only be performed bv”
( ) Set the Receiver controls as follows:
those who
ience.
have instrument alignment exper -
SOURCE switch to @ FM.
PHASE switch pushed in.
IF ALIGNMENT
Equipment needed: A high impedance input DC
VTVM, and an RF generator that is accurate at
10.7 mc, A Heathkit VTVM and the Heath-
kit FM0-1 Test Oscillator, or their equiv-
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
alents, may be used,
I
the Alignment Chart below.
IF ALIGNMENT CHART
PREPARATION
Connect a jumper
wire between
points X and Y
on the FM-
Multiplex
circuit
board.
Remove
jumper
wire from between
points X and Y.
Connect
To
A n t e n n a
~ i n p u t
terminals.
Antenna
input
terminals.
GENERATOR
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.
-GGJ-
AOJUS
Connect
To
I
Transformer
I
I
I
Bottom slug
of T6
TPl
I1
T
I
Top and bottom
slugs of T5
I
Top and bottom
slugs of T4
TPl
Top and bottom
slugs of T3
t-
Top and bottom
slugs of T2
t
Repeat each step
above until no
further
improve-
ment is obtained.
1
1
TP2
Top slug of
T6
TP2
If necessary,
readjust top
slug of T6.
For VTVM
Reading
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:
Audio generator and &4C
VTVM. The Heathkit Models IG-72 or IG-82
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 R,
See Figures 4 and 5 (fold-out from Page 65),
Complete the steps in the Stereo Alignment Chart
and the steps
that follow the chart.
PHASE con-
trol to about
2 o’clock
position.
Push PHASE
switch in.
Adjust
AND
switch to M FM.
PHASE switch
pulled out.
STEREO ALIGNMENT CHART
AUDIO GENERATOR
Connect To
Negative
(-) lead
of capac-
itor C39.
Frequency
And
output
38 kc (~200 cps)
. 01 volt rms
output.
67 kc .l volt
rms output.
(
) 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.
VTVM
Connect To
TP3
Coil
L8
L6
ADJUST
For VTVM
Reading
Maximum
reading (about
.2 volt rms).
Minimum
reading (about
. .007 volt rms).
This completes the Stereo Alignment,
CHANNEL SEPARATION TESTS
If an FM stereo generator is available, this
generator may be used to check channel separa-
tion. To check separation, coil L7 and transform-
er T7 must be adjusted as outlined in the follow-
ing 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 R,
Connect the
FM
stereo generator output
(
>
>
3 .
Turn the slug clockwise l/4 t u r n .
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.
ise
the
lead to the negative (-) lead of capacitor
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.
( ) 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,
usually expressed in
db
(decibels).
) Set the FM stereo generator to the right
channel output and use the 19 kc pilot signal
with a 1 kc multiplex signal.
) Adjust coil L7 for maximum brilliance of
the stereo indicator lamp.
( ) Pull out the PHASE switch, then a d j u s t the
PHASE
control
fully
clockwise.
NOTE: Complete the following adjustments very
carefully to obtain good stereo listening.
( ) Adjust transformer T7 as follows:
1.
Turn the slug (not more than one turn
in either direction) until the sound out-
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.
(
>
(
)
(
1
(
>
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.
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 be-
tween these two readings.
Disconnect the FM stereo generator, AC
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 Tests.
SPECIFICATIONS
FM SECTION
Tuning Range. . . 0 0 0 0 .
0
0
0
0
0
0
0
0
0 0.00..
Antenna Input Impedance. . . . . . . . . . . . . . .
Sensitivity, . 0.00..
Intermediate Frequency (IF). . 0.00..
0 0 0 0 0
Hum And Noise. ..o.ooooooooooooooooo
Audio Frequency Response. . . . . . . . . . . . . . .
Harmonic Distortion. . . . . . . . . . . . . . . . . .
Image Ratio.
Capture Ratio. 0.00..
AFC Correction. . . . . . . . . . . . . . . . . . . . .
AM Suppression. . . . . . . . . . . . . . . . . . . . .
IF Rejection. . . . . . . . . . . . . . . . . . . . . . .
Separation. .
0 0 0 0
0 0 0
0 0 0 0
0 0 0
0 0 0 0
0 0 0 0 0
88-108 mc,
300 0, balanced input.
5 microvolts,*
10.7 mc,
-50 db, 1 watt reference.
Monophonic
: 0 to -3 db from 20 to 15,000 cps.
1% or less.*
-45 db,*
3 db,*
150 kc per volt.
-35 db,*
-80 db,*
30 db at 1000 cps.
AMPLIFIER
SECTION
Continuous Power Output.
channel.
0
0
0 .
.
0 0
0
0
0
10 watts per
Music Power Output. . 0 0
channel.*
0
0
0
0 0 0 0 0 0 0 0
0
0
0
15 watts per
Speaker Output Impedance.
.
0
0 0 0 0 0 0 0 0
0
0
0
4 through 16 0.
Tape Output Impedance. .
3500 cl.
0
0
0
Damping Factor, .
50 or higher.
Hum And Noise,. . . . . . . . . . . . . 8.. . . . . .
Phono:
-60 db; 10 MV reference-input shorted.
Auxiliary: -63 db; input shorted.
*Rated IHF (Institute of High Fidelity) Standards.
5
5
4
4
3
3
2
2
1
1
D
D
C
C
B
B
A
A
300 ^
ANTENNA
CONNECTOR
AGC
AFC
+8V
Heathkit FM Radio AR-14
RF AMPLIFIER
MIXER
LOCAL OSCILLATOR
IF a
IF b
AGC
+8 V
AFG
Z
C17
10pf
R2
2.7K
R8
1.2K
C18
.02mf
C20
.02mf
X
C3
5.6pf
C21
.02mf
C10
1.5pf
R3
10K
L2
R6
4.7K
T2
T
C8
2.5pf
R5
10K
Y
C13
12pf
C2
6.8pf
R4
1K
U
C16
10pf
2
S
L3
Q1
2SA240
R1
470
R7
2.7K
C5
.02mf
C14
C15
.02mf
C6A
D1
C1A
C12
120pf
C7
15pf
Q3
2SA239
C14A
C9
.02mf
C6
T1
Q2
2SA240
C19
15pf
C1
C11
.02mf
L4
1
5
5
4
4
3
3
2
2
1
1
D
D
C
C
B
B
A
A
1
2
BLK
1600 V
3
4
BLK-RED
BLK-GRN
BLK-YEL
1
BLK-YEL
BLK-GRN
BLK-RED
4
3
1600 V
BLK
2
240 VOLT WIRING
POWER SUPPLY
TREBLE CONTROL
POWER SWITCH ON
120 VOLT WIRING
POWER SWITCH
ON TREBLE CONTROL
120V
AC
AC SOCKET
E +28V
A +38V
B +17V
C +8V
D +28.6V
F +26.8V
R202
150 1W
+
C206
100mf
P1
PLUG
PLUG
R207
820
A
R200
75 5W
+
C202
500mf
F1
1 Amp Slow Blow
T8
R203
220 1W
+
C207
100mf
R208
1.5K
B
F
+
C203
500mf
R204
270 1W
C200
.01 MF
-
+
D1
+
C204
100mf
F1
1/2 Amp Slow Blow
LAMP 47
T8
G
R205
6.8K
R201
330 5W
C
C200
.01 MF
Q100
2N2712
+ C205
100mf
PILOT LIGHT
R206
47K
1
2
1
2
D
+
C201
4000mf
E
5
5
4
4
3
3
2
2
1
1
D
D
C
C
B
B
A
A
1ST IF AMPLIFIER
2ND IF AMPLIFIER
3RD IF AMPLIFIER
AGC
RATIO DETECTOR CIRCUIT
4TH IF AMPLIFIER
TO STEREO MULTIPLEXER
IF a
IF b
AGC
Q8
AFG
+8 V
C +8 VOLTS
R18
270
R25
1K
R9
33
R32
1 MEG
R24
1.2K
T4
C41
680pf
R28
6.8K
R14
10K
R16
1.5K
T1
IF FM
L5
90 uH
C28
.01MF
C30
6.8pf
Q4
2N2654
C25
.01mf
C32
.01MF
R53
47K
Q7
2N2654
R10
3.3k
Q6
2N2654
C29
.01MF
C40
400pf
R15
5.6K
R30
1.5K
C22
470pf
+
C39
10mf
C21
150pf
T3
R19
5.6K
L6
R11
33
R17
1.5K
R22
270
R21
1K
C36
270PF
C31
.01MF
+
C35
5MF
R20
1.5K
C33
270pf
+
C24
10MF
T5
C26
.01MF
R12
3.3k
C37
.01MF
R29
6.8K
R26
470
C27
.01MF
R31
150
R23
5.6K
R27 1K
C23
.01MF
R13
1.5K
Q5
2N2654
D2
C34
270pf
5
5
4
4
3
3
2
2
1
1
D
D
C
C
B
B
A
A
STEREO
INDICATOR
PHASE
38KC
OSCILLATOR
ON PHASE
ADJUST CONTROL
AUDIO AMPLIFIER
AMPLIFIER AND
EMITTER FOLLOWER
19 KC
6
3
4
Q8
STEREO LEFT
STEREO RIGHT
B +17V
C +8V
C45
390pf
R40
220
C58
.002MF
C48
.2MF
C53
470pf
Q8
2N2712
C49
2700pf
R33
33
Q14
2N2712
R50
10K
R51
220K
R43
10K
C50
.01MF
R37
2.2K
R41
47K
R46
6.8K
R44
560
R49
47K
R.E.C.
2
3
1
Q9
2N2712
+
C56
10MF
+
C59
10MF
C55
.001MF
C51
.01MF
ADJ
NORMAL
R38
47K
C41
680pf
R47
2.2K
C42
.01MF
C44
.01MF
R35
120K
Q11
2N2712
L8
R.E.C.
2
3
1
R42
560
R48
15K
C46
.01MF
R39
10K
L7
5
1
4
2
R34
1K
Q10
2N2712
T7
1
6
2
5
3
4
7
+
C52
10MF
Q12
2N2712
R45
39K
C57
.002MF
+
C43
10MF
C47
.01MF
Q13
2N2712
R36
68K
REAR OF
WAFER #3
R52
220K
C38
200pf
LAMP
C54
.001MF
5
5
4
4
3
3
2
2
1
1
D
D
C
C
B
B
A
A
AUX
RIGHT
FM
RIGHT
PHONO
LEFT
FM
LEFT
AUX
LEFT
PHONO
RIGHT
FRONT-OF
WAFER-#2
REAR-OF
WAFER-#2
FRONT OF
WAFER #1
CLOSE FOR MONO
OPEN FOR STEREO
TAPE OUTPUT
TAPE OUTPUT
PHONO
PHONO
AUX
AUX
FM
FM
REAR OF
WAFER #1
WAFER #1
REAR OF
STEREO RIGHT
STEREO LEFT
AF LEFT
AF RIGHT
F +26.8V
E +28V
F +26.8V
E +28V
11
2
R128
39K
27
R112
R56K
R113
56K
5
4
R106
180K
Q4
2N2712
R183
15K
19
C105
.0068MF
R111
56K
23
+
C103
100MF
28
R127
39K
14
4
R115
390
R121
100
2
20
5
6
R116
390
6
R109
4.7K
12
R124
100
C105
.0068MF
+
C107
10MF
R118
390K
R103
180K
+
C102
10MF
R105
180K
R126
820
10
3
3
22
Q3
2N2712
11
12
R102
1K
10
R114
56K
15
18
9
3
C106
.0022MF
Q1
2N3391
R181
2.2K
10
9
1
Q2
2N3391
R117
390K
5
16
R125
47K
R123
820
10
R179
1K
R180
1K
R120
47K
R122
10K
2
R119
10K
2
3
4
11
10
R184
15K
12
+
C108
100MF
11
R108
4.7K
R110
4.7K
10
3
9
R129
10K
R130
10K
C109
.0022MF
13
12
9
17
R104
180K
24
8
8
9
R101
1K
+
C110
10MF
R107
4.7K
5
8
7
R182
2.2K
6
21
8
+
C101
10MF
5
5
4
4
3
3
2
2
1
1
D
D
C
C
B
B
A
A
LEFT CHANNEL
SPEAKER OUT
4 THROUGH 16 OHMS
AUTIO AMPLIFIER
LEFT CHANNEL
AF LEFT
E +28V
D +28.6V
A +38V
A +38V
Q15
2N2148
C131
.1MF
+
C119
2MF
+
C129
2500MF
25
R131
5.6K
Q5
2N2712
R157
1K 1/2 W
C111
.047MF
Q7
2N2712
R165
150 1W
31
+
C125
500MF
45
37
+
C113
10MF
R173
560
+
C117
10MF
R151
100K
R145
6.8K
43
R167
150 1W
R149
6.8k
R177
100 1/2 W
Q11
2N3053
D101
1N3754
R161
2.2K
R169
1^ 2W
R175
560
S1
C131
.005MF
R141
50K
C121
10pf
Q9
2N3416
R171
1^ 2W
R135
5.6K
J4
PHONEJACK STEREO
1
2
3
C115
.002MF
33
47
R163
91 1/2 W
R137
5.6K
39
R153
33K
A
41
35
R143
5.6K
R147
100K
R185
10
R155
100K
R133
50K
Q13
TA2577A
R159
100
C123
.003MF
R139
39K
+
C127
500MF
29
5
5
4
4
3
3
2
2
1
1
D
D
C
C
B
B
A
A
SPEAKER OUT
4 THROUGH 16 OHMS
RIGHT CHANNEL
RIGHT CHANNEL
AUTIO AMPLIFIER
AF RIGHT
A +38V
A +38V
D +28.6V
E +28V
R132
5.6K
C132
.005MF
R168
150 1W
36
+
C120
2MF
+
C130
2500MF
R166
150 1W
C124
.003MF
46
R140
39K
+
C126
500MF
Q12
2N3053
R174
560
Q10
2N3416
42
R144
5.6K
R178
100 1/2 W
D102
1N3754
R172
1^ 2W
R146
6.8K
Q14
TA2577A
Q6
2N2712
+
C118
10MF
R176
560
+
C114
10MF
R136
5.6K
R152
100K
Q16
2N2148
S1
R186
10
R142
50K
44
R170
1^ 2W
Q8
2N2712
32
+
C128
500MF
J4
PHONEJACK STEREO
1
2
3
R162
2.2K
R159
100
A
R158
1K 1/2 W
R164
91 1/2 W
C122
10pf
R156
100K
48
30
34
R154
33K
C132
.1MF
26
40
C112
.047MF
R150
6.8k
C116
.002MF
R134
50K
38
R138
5.6K
R148
100K