National Criterion User manual

INSTRUCTION BOOK FOR
The National
AM-FM TIMER
The NationalCriterion isa superb, 14-tube super-
heterodyne tuner offering the utmost in versatility
and performance.Designed foruse either with or
without the NationalHorizon 5 preamplifier, the
Criterion is completelycompatiblewith all standard
high fidelitymusicsystems as well asthe National
Horizon series of amplifiers. In addition tothe usual
features found in highqualitytuners, the Criterion
offers binaural reception, freedom from adjacentchan-
neland co-channel interference(accomplished ,by its
unique design, and highcaptureratio),provision for
multiplex operation,plus a panel-selected FMMu-
tamatic circuit. Itmaybe used asa self-contained
unit housed inits colorfulprotectivedustcover or
mounted, withextremesimplicity, into any cabinet
or panel ofthe user's choice.
CASCODE FRONTEND:Provides the maximum
possible sensitivity intheFM frequency range.
FM IF CHANNEL: 8 tuned circuits are used to pro-
vide a highly selective intermediate frequency pass
band. This enables the selection of adjacent-chan-
nel stations withoutintroducinginter-channel inter-
ference.
CAPTURE EFFECT: The extremelyhighcapture
ratio of0.8 eliminatesannoyinginterference from
weaker signals inthe samechannel asthe desired
signal.
INSTANTANEOUS LIMITER: 2 cascaded 6BN6's
with instantaneouslimitingaction are used to elim-
inate the shortimpulseinterference so characteristic
atFM frequencies. This type of limiting also con-
tributes tothe tuner'shighcapture ratio.
WIDE BAND DISCRIMINATOR: The widefrequency
response and freedom from critical tuning oftheFM
channel is made possible bytheuseofan exception-
ally widebanddiscriminator circuit.
Please use this manual. It has been prepared with the prime purpose of enabling the user to obtain
full satisfaction from this product.
NATIONAL COMPANY, INC.,
MAIDEN & MELROSE,MASS.

HATIO OF
DESIRED
TO
UNDESIREO
SIGNALS
OH THE SAME
CHANNEL
1.5
1.4
1.3
I.IS—
1.2
I.I
I
.9
.1
.7
.6
.8
.5
.1
DESI AL
REGION OF
COMPLETE
REJECTION OF
UNOESIRES
SIGNAL
RATIO OF AUOIO INTERFERENCE
0 I
UNOESIRED SIGNALS
DESIRED SIGNALS
^_
REGION
OF
COMPLETE
ACCEPTANCE
OF
UNOESIRED
SIGNAL
Figure 7. Capture Ratio Characteristics
IIMF *f >
Figure 2. Quieting Sensitivity Including Theoretica I Noise Limitations
-2-

100 0 100 200
FREQUENCY KILOCYCLES
FREQUENCY KILOCYCLES
Figure 3.FM Selectivity Characteristic Curve
Figure 4.AM Selectivity Characteristic Curve
SIMULTANEOUS AM-FM: Two independentchan-
nels are used,each with individualtuning and volume
controls, to provide this uniqueflexibility of opera-
tion.
BINAURAL PROVISION: The tuner maybe used
to receivesimultaneous binaural AM-FM broadcasts
and feed them toany binauralaudiosystem.
MULTIPLEX PROVISION: This featureprovides
for the latest in broadcastingtechniqueswhich use
the multiplexsystem for binauraltransmissions.
FM AGC: AGCis utilized intheFMas well asthe
AM section ofthe tuner to maintain the optimum in
passband characteristics oftheIF amplifier.
OVERLOAD CHARACTERISTIC: The front endde-
signprovides a highdegree of freedom from overload
and spurious responses as well as60dbof image re-
jection. A four sectiontuningcapacitor is used in-
stead ofthe usual twoor three section type.
AM SELECTIVITY: TheAM portion ofthe tuner
has beendesigned specifically to providefaithful
audioreproduction upto8 kc.TheIF pass band is
adequate to providesatisfactoryhighfidelityper-
formance. The overall sensitivity is sufficient toin-
sure optimum quieting onany signal strongenough to
providehighqualityaudio.
PREAMPLIFIER: A removableplate onthe front
panelpermits the insertion ofthe NationalHorizon 5
preamplifier, bringing allthe desiredcontrols and
compensationfeaturesrequired for high fidelity
phonograph reproductiondirectly tothe front panel
of the tuner.
PRINTED CIRCUITS:Printedcircuitry is used to
take full advantage ofthe latest electronictechni-
ques, resulting in completeuniformity in manufactur-
ing, freedom from drift, and conservation of chassis
space.
LOW IMPEDANCE OUTPUT:Cathodefollowers
are used to provide low impedanceoutput to permit
the useof longeroutputcablelengths.
FM MUTAMATIC: An efficient squelchcircuit is
provided to eliminate inter-station backgroundnoise
when tuning. The Mutamatic feature maybe switched
out when tuning weak signals.
RECORDER OUTPUT: A constantleveloutput is
available, which isnot affected bythe volume con-
trols, to provide a constantaudiolevel foruse with
recordingequipment.Thisoutput isa moderate im-
pedanceoutput. De-emphasis hasnot beenincluded
to permit useof longshieldedinterconnecting cables
without excessive loss of highfrequencies.
HUM LEVEL: The level ofhum throughout the
tuner is maintained at60db below the ratedoutput.
FM TUNING CAPACITOR: A four-section tuning
capacitorprovidesexcellentselectivitycharacter-
istics, atthe same time contributing tothe freedom
of front-end overload.
AM DETECTOR: A high-fidelity,low-distortion de-
tector is used to take full advantage ofthe wide-band
IF characteristics.
INTERLOCKS: All shockhazard is avoided bythe
incorporation of interlockswitches intheAC primary
circuit.
DRIFT: The effect of oscillator drift is negligible
without resorting to troublesome AFC circuits.
FM DISTORTION: The total FM distortion is essen-
tially zero.
POWER INPUT: 117 VAC, 60 cps, 80 W, 0.7 amp.
-3-

TO
RECORDER
117 VAC 60 ~
TOAM
ANTENNA GROUND TOAM
IF USEDANTENNA
FM ANTENNA
WITHOUT PREAMP
NATIONAL CRITERION
TUNER
NATIONAL HORIZON
AMPLIFIER
INPUT
FM ANTENNA
WITH HORIZON 5 PREAMP
117 VAC 60 ~
FM ANTENNA
BINAURAL
TO AM
ANTENNA GROUND
IF USED
NATIONAL CRITERION
TUNER
NATIONAL HORIZON
AMPLIFIER
*MAY BE LEFT IN TUNER
OUTPUT JACK IF DESIRED.
**WHEN TUNER IS EQUIPPEDWITH
PREAMP, MOVE THISLEAD TO
"PREAMP OUTPUT"JACK.
NATIONAL HORIZON
AMPLIFIER
Figure 5. Typical Installation Plans

PREPARING TO OPERATE
Examine the tunerimmediatelyafterunpacking to
make certainthat no apparentdamage has been in-
curred duringshipment. Donot discard any packing
material until allthe followingitemshavebeen lo-
cated aud identified.
1AC linecord (if tuner is withoutdustcover)
1 4-foot shieldedaudiooutputinterconnectingcable
1FM twinleadindoorantenna
1 AM indoorantenna
1 Consolemounting strip
3 Wood screws for mountingstrip
NOTE: Inthe case ofthe tunersupplied less the
dustcover, two metal strips are fastened atthe ends
of the underside ofthe chassis to facilitatepacking.
These strips should be removedimmediately after the
tuner is taken from the carton. The tunercannot be
mounted with these strips in place. Refer tothe
paragraph on Cabinet Installation.
ELECTRICAL CONNECTIONS
All the input and outputconnectors ofthe Criterion
tuner are located onthe backdrop ofthe chassis.
See Figure 5. Connections tothe variousjacks
should be made inthe following manner:
TUNER OUTPUT: This connector is used when
the tuner isnot equipped with the plug-in preamplifier
Connection maybe made tothe main poweramplifier
or tothe preamplifier if this unit is mounted separate-
ly from the tuner. The tuner supplies upto3 volts
of audio on either FMorAMat this pointwhich is
ample forthe National Horizon series of amplifiers
as well asthe majority of highqualityamplifier units.
The four-foot cable furnished with the tuner is fitted
with properplugs to make connection tothe National
amplifiers. When connecting to other amplifier equip-
ment itmaybe necessary to modify oneendofthe
cable to suit the requirements ofthe amplifierinput
connector. In such cases, make certainthat the
shield braid is grounded. Since the Criteriontuner
provides a low impedanceoutput, the cable length
may be increased toas much as20 feet if desired
without affecting frequency response.
RECORDING SIGNAL OUTPUT:Thisjack is pro-
vided for makingconnections tothe input of most
standardtape or discrecorders.This isa high im-
pedanceoutputwith a constantlevel ofone volt rms
which isnot affected bythe volume controls ofthe
tuner. The output is switchedbetween AMorFMas
selected bythe Selectorswitch.
FM-AM BINAURAL OUTPUTS: These two jacks
provide low impedanceoutputs from theFM section
and AM section respectively.They are intended to
be used with two independentamplifier-speaker
systems for binaural reception of simultaneous AM-
FM broadcasts. The cable specifications forthe
Tuner Outputjackwill also apply tothe Binaural
Output jacks.
TAPEPLAY BACK INPUT: This jack maybe
usedonly when the Nationalplug-inpreamplifier is
used in conjunction with the tuner. The output ofa
taperecorder orany similaraudiodevicewith ap-
proximately one volt or more output maybe perma-
nently connected to this jack and selected when the
Selectorswitch onthe preamplifier isinthe Tape
position.
TV INPUT: A one-volt audiosignal from a TV
tuner maybe connected to this jack and selected at
theTV position ofthe preamplifierSelectorswitch.
Probably the mostconvenientpoint for obtaining this
voltage is across the volume control oftheTV set.
WARNING
Sincehighvoltages are present inTV receivers
this connectionshouldonly be made bya com-
petent TV serviceman.
PHONO INPUT:HighFidelityphono equipment
utilizing magnetic or reluctancetypecartridges may
be connected tothe Phono Input jack. The plug-in
preamplifier has provisions for accommodatingeither
the10or 30-millivolt typecartridge. A slide switch
on the preamp is accessible through a cutout in both
the preamp and tunerdust covers. Slide this switch
toward the panel for30 mv. pickups and toward the
rear for10mv. pickups. When the selector switch is
setatanyoneofthe sevenrecordcompensation
positions the phonopickup is connected tothe pre-
amp circuits andthe Selectorswitch maybe used to
provide the desiredcompensation.
PREAMP OUTPUT: When the Criteriontuner is
equipped with the plug-in preamp, the PreampOutput
jack is used, in place ofthe Tuner Output jack, for
connecting the tuner tothe main amplifier. Byso
doing, all the switching and controlfunctions ofthe
preamplifier are used to adjustvolume and tone for
the system.Thisbringsintoplay the Loudnesscon-
trol ofthe preamplifier so thatspeakeroutput canbe
varied with automatic frequency compensation.
FM MULTIPLEXONLY: This jackprovides a high
impedance output from theFM section ofthe tuner
only.Multiplextransmissions of binauralprograms
are contemplated bythe broadcastingindustry atthe
-5-

presenttime. When theFM stations start transmitting
this type of signal, equipment will be available for
connection tothe Criteriontuner for separation of
the multiplexed signals.
A.C.OUTLETS: Two A.C. outlets are provided for
convenience in connecting other units ofthe system.
Units connected to theseoutlets are turned onand
off bythe A.C.switch onthe tuner or preamp.
OPERATING INSTRUCTIONS
The National Criterion tuner isan extremely versa-
tile instrument andmaybe operatedwith or without
the NationalHorizon 5 preamplifier.
1. OPERATION WITHOUT THE PREAMPLIFIER
Two separate tuningcontrols are provided,each
having itsown calibrated slide-rule dial. The volume
controls for AM andFM reception are located adjacent
to theirrespectivetuningknobs. The remainingcon-
trol selects the desired mode of operation(AM, FM,
Binaural or Mutamatic). The On-Off switch'is, part of
theAM volume control andis disabled when the pre-
amp is plugged in.
a.To tune anAM signal first setthe selector con-
trol atAM. Adjust theAM tuning control tothe fre-
quency ofthe desiredbroadcast station and adjust
theAM volume control to suit.
b.To tune anFM signal setthe selectorswitch at
FM MUTAMATIC. In this positiontuning tothe de-
sired signal is accomplished without annoyinginter-
station background noise. Adjust the tuningcontrol
tothe channel desired andsettheFM volumecontrol
to suit. If die signal beingtuned is very weak itmay
be desirable tosetthe selector switch atFM rather
than FM MUTAMATIC. This permits a station tobe
heard which normally would notbe strongenough to
override the squelchthreshold.
c. Binauraloperationrequires theuseoftwo com-
plete amplifier-speaker installations. To operate the
Criteriontuner with this type of equipment setthe
selectorswitch atAM. Tune the desired signal by
means oftheAM tuningcontrol and adjust the volume
tothe proper level. Switch the selector toFMand
tune the same broadcast ontheFM band using the
FM tuning andFM volume controls. Setthe selector
switch at Binaural. Note: The proper setting ofthe
volume controls will be determined bythe require-
ments ofthe associated binaural audioequipment.
d.If "off the air"recordings aretobe made and
the recorder is properlyconnected tothe Recording
SignalOutputjack, the tuningprocedure may follow
either a.orb. above. The volume controls maybe
adjusted for desired listening levelwithoutaffecting
the 1-volt rms level reaching the recorder. The re-
corder volume control is adjusted for properrecord-
ing level.
2. OPERATION WITH THE PREAMPLIFIER
When the NationalHorizon 5 preamplifier is used,
the tuner is operated inthe same manner as above
exceptthat forAMorFM receptionbothvolumecon-
trols aresetat maximum andthe Loudness control
of the preamp is used to adjust the audio level. The
switch portion ofthe Loudnesscontrol now functions
asthe ON-OFFswitch for both the tuner and preamp.
To receive binaural signals when the preamp isin
the tunerfirst settheFM volumecontrol at maximum.
Adjust the Loudnesscontrol ofthe preamp tothede-
siredlistening level. SettheFM volume control at
minimum. Adjust theAM volume control tothe de-
sired level withoutdisturbing the Loudnesscontrol.
Return theFM volumecontrol to maximum. Make all
further level adjustmentswith the Loudness control.
The Selector switch onthe preamp must besetatthe
Tuner position. The other settings ofthe Selector
are covered in detail inthe instructionsaccompany-
ingthe preamp. The widerange ofthe Bass and
Treblecontrols maybe used to full advantage.
CABINET INSTALLATION
Mounting the Criterion tuner into a cabinet or panel
is extremelysimple. Only one7 by15 inchhorizon-
tal cutout is required.Primaryconsiderationshould
be given tothe cutoutlocation in terms of outward
appearance, control accessibility etc. Since the
tuner is installed through the front ofthe cabinet,
connections atthe rear ofthe chassis need notbe
accessible from the rear ofthe cabinet. All con-
necting cables, providedtheyhavesufficient slack,
may be pluggedinto the tunerthrough the panelcut-
out before sliding the tuner into place.
When the desired cutout location has beendeter-
mined layoutthe rectangle, makingcertainthat itis
square with the sides ofthe cabinet. Use care in
making the cutsbeingparticularly careful tosee that
the bottom edge ofthe cutout is straight and level.
Refer to Figure 6 forthe proper method of securing
the mounting strip. The mounting strip supplied is
marked FRONT along one edge.Thisedge must be
flush with the front surface ofthe cabinet. The tabs
protruding from the ends ofthe strip must point up-
wards toward thetopofthe cutout. Six screwholes
-6-

7"
15"
Ftgun 6. Meffcot/ of Mounting Tuner in Custom Cabinet
ate provided. Ifthe cabinet is constructed of3/8
inch or thickerstock, the three front holes are used
to secure the strip tothe bottom edge ofthe cutout.
If the stock is1/4 inchthick or less, a strip of wood
at least 1/2 inchthickmust be gluedalong thein-
side ofthe cutout flush with the bottom edge. This
willsupplysufficientthickness to hold the screws
andthe threerearholes ofthe mounting strip may
be used.
Once the mounting strip is secured tothe cabinet
all that is required isto slide the tuner through the
cutout with thetopofthe panel tilted towardyou.
When the slots in die bottom of die tunerengage the
studs inthe mounting strip, release thetopofthe
panel. The weight of die tuner chassis willhold
die unit securely inthe cabinet.
REMOVAL FROM CABINET
If die tuner has beenproperlymounted ina custom
cabinet itis onlynecessary to tilt die topof die
paneltowardyou,lift die panelabout 1/4 inch to
clear the mounting studs and withdraw die tuner far
enough to disconnect the input and output cables
after which the tuner maybe removed from die cabi-
net.
If die tuner is equipped with a metaldustcover,
remove die four feltfeet from die bottom of die dust
cover and slide die tuner outof die cover. When re-
placing die tuner use care to align die AC interlock
connection between die chassis and dust cover.
Removal of die plug-inpreamplifier is accomplished
by loosening the captive thumbscrew at each endof
die preamp panel and withdrawing the preamp. To
re-install simplyreverse die above procedure.
REALIGNMENTPROCEDURE
1. FM IF ALIGNMENT
The superior performance of die NationalCriterion
tuner is due, ina largemeasure, to die excellent
characteristics of die IF amplifier,cascade limiters
and widebanddetector. Alignment of diese stages
should notbe undertaken by means of die customary
peaking mediods. Only a competentserviceman
equipped widi the following specialized test instru-
ments should perform this alignment.
1. Harvey205TSSweepGenerator or equivalent.
2. Dumont 208 Oscilloscope or equivalent.
3.RCA WG-264 R.F.Probe or equivalent.
4. TankLoading Resistor-1000 ohms, 1/2 watt.
5. Tuning Wand such as General Cement no. 8606-D.
-7-

FRONT
HUM SQUELCH
BALANCE THRESHOLD
R72 R58
TEST POINT NO. 2
TOP VI£W OF CHASSIS
TEST POINT NO. 4
TEST POINT NO. 3
FRONT
4-
<™®}'®Ww>
© !! (PLIZB;
1©L"B®M©^_®)
^SEC SEC
f@Z2®) |®ZI®1
^L22B,
II
II
(© "®J 1© ®!
® T8 © \SK,
'®U8B®J.
O
^
®J
BOTTOM VIEW OF CHASSIS
Figure 7. Alignment Adjustments and Test Point Locations
-8-

6. SignalGeneratorproviding10.7 me. and455kc.
marker signals.
During normal useofthe Criteriontunerrealignment
will notbe required.Changing tubes will not appre-
ciablydisturb the alignment.Only inthe event ofa
major repair or severe damage wil1 itbe necessary
to completelyrealign theIFor limiter stages and
cautionshould be exercisedbeforedisturbing any
adjustments.
a. CHECKING IFFOR PROPER ALIGNMENT
The first step inthe alignment process isthe
observation oftheIF characteristic onthe oscillo-
scope. See Figure 7 for alignmentadjustment and
test point locations. Proceed as follows:
Step 1. Connect the sweepgeneratorbetween the
grid (pin 7)of V2 and chassis. This is mostcon-
veniently accomplished by connecting the "hot"
lead from the generator to test point no.1 andthe
ground lead tothe frame oftheAM tuning capacitor.
Alsoconnect a 10-ohm resistor from pin7 ofV2to
ground.Short leads must be used.
Step 2.Setthe generatorcenter frequency at 10.7
me. with a 4-mc. sweep deviation.
Step 3. Short theFMAGCto ground by means of
a jumper between test point no.2 (junction ofC33
and R47) and chassis.
Step 4. Connect the oscilloscope totheIF ob-
servationpoint, test point no.3 (junction ofR35and
C47),using a 60-cycle sweep.
Step 5.Setthe selector switch ofthe tuner tothe
FM Mutamatic position.
Step 6. Adjust the output ofthe sweepgenerator
toa leveljusthighenough to provide a usable scope
pattern.
Step 7. Readjust the generatorsweepwidth and
center frequency to produce the optimum view ofthe
IF pass band. The scope patternshouldappear asin
Figure 8A.The minimum possible inputmust be
used. Too much signal willdistort theIF pass band
pattern.
Step 8.Ifthe scope pattern isnot symmetrical,
check the adjustment ofT4by means ofthe tuning
wand and readjust to obtain the correct scope pattern.
In most cases this adjustmentshouldrestore theIF
alignment to properoperating condition. Ifit does
not doso, proceedwith the completerealignment.
b. DETAILED FMIF ALIGNMENT
If the previous steps indicate the necessity for
complete realignmentproceed as follows:
Step 1. Connect the sweepgenerator to test point
no.1 using a 1000 ohm resistor in series with the
"hot"lead anda 10-ohm resistor from grid to chas-
sis.Step
2. Using theRF Probe, connect the oscillo-
scope tothe plate ofV5, (pin 5).
Step 3.Setthe sweepgeneratorcenter frequency
at 10.7 me. with a sweeprate of60 cycles anda
sweep width ofat least 300kc.Setthe marker sig-
nal at 10.7 me.
Step 4. Using test clips with short leads, connect
the 1000-ohm resistor across the primary ofT4.
Step 5. Reduce the generatoroutput toa level
just highenough to produce a usable scope pattern.
The patternshouldappear asin Figure 8B.
Step 6. TuneL11A and LI IB of T2 for maximum
gain as indicated bythe vertical size ofthe scope
trace, atthe sametimekeeping the trace precisely
centered onthe 10.7 me. marker.
Step 7. Move the 1000-ohm resistor tothe primary
of T6and move theRF Probe tothe plate ofV6 (pin
5).
Step 8. Adjust L13A and L13B ofT4for maximum
gaincentered on 10.7 me. Maintain the minimum pos-
sible generatoroutput for usable scope pattern.
Step 9. Move the resistor tothe primary ofT8.
Remove Vll from its socket. Connect theRF Probe
tothe plate ofV8 (pin 7). Adjust L16A and L16B
of T6inthe manner outlined in Step 8.
Step 10. Short theAGCbusby connecting a
jumper between test point no.2 and chassis.
Step 11. Connect the oscilloscope to test point
no.3 using theDC probe.
Step 12. Adjust L18A and L18B ofT8for opti-
mum IF passband, keeping the generatoroutput at
minimum. This willcomplete theFMIF alignment.
Remove theAGC jumper unless detectoralignment
istobe performed,
c.FM DETECTOR ALIGNMENT
For normalalignment oftheFM detectoronly a
slight readjustment ofZ2 will be required. To ac-
complish this proceed as follows:
Step 1. Connect the oscilloscope attheFM Out-
put jackJ2B.
Step 2.Setthe selector switch ofthe tuner at
FM Mutamatic andsettheFM volumecontrol atits
maximum clockwise position.
10.7 MC. MARKER
Figure 8. Alignment Waveforms
-9-

Step 3. Connect the sweepgenerator and short
the AGCasin paragraph b. above.
Step 4. Vlith the generatoroutputleveljusthigh
enough to produce a usablepattern, the traceshould
appear asin Figure 8C.
Step 5. Adjust L22A ofZ2for maximum linearity
of the trace.
Step 6. Remove all test equipment.
2. AMIF ALIGNMENT
TheAMIF amplifier ofthe Criteriontuner has been
designed for widepassband characteristics while, at
the sametime,providing optimum selectivity consis-
tentwith this characteristic. IF Alignment bythe
usualpeakingmethodswouldjeopardize the overall
performance. The followinginstructions must bead-
hered to.
Step 1. Connect the sweepgenerator tothe control
grid oftheAM mixer (pin 7 of V4). Usea 1000-mmfd
capacitor in series with the "hot" lead.
Step 2.Setthe generatorcenter frequency at455
kc. with a 50-kc.sweep and supply a marker at455
kc.
Step 3. Connect the 1000-ohm resistor across the
primary ofT5.
Step 4. Using the R.F.Probe,connect the oscil-
loscope tothe plate ofV5 (pin 5).
Step 5.Set die selector switch ofthe tuner toAM.
Step 6. Adjust the generatoroutput toa level just
high enough to produce a usable trace. The pattern
shouldlook like Figure 8A.
Step 7. Adjust L12A and L12B ofT3for maximum
gain,keeping the patternsymmetrical and centered on
the 455-kc. marker.
Step 8. Move the 1000-ohm jumper tothe primary of
T7and adjust L14A and L14B ofT5asin step 7.
Step 9. Remove the 1000-ohm jumper and connect
the oscilloscope totheAMIF observationpoint,
test point no.4.
Step 10. Adjust L17A and L17B ofT7for optimum
bandpass characteristics. Remove test equipment.
LOOP CORD
AROUND PULLEY
POSITION POINTER AT CENTER
OF DIAL MARKING 55
AROUND SHAFT
FASTEN CLIP
HERE
AM DIAL
CORD ASSEMBLY
SETAM TUNING
CAPACITOR AT
MAXIMUM MESH
LOOP CORD
AS SHOWN
PASS CORD THRU
POINTER SLIDER
LOOP CORD
AROUND PULLEY
FASTEN SPRING
HERE
FASTEN CLIP
HERE
SETFM TUNING
CAPACITOR AT
MAXIMUM MESH
LOOP CORD
Ij TURNS
AROUND SHAFT
FM DIAL
CORD ASSEMBLY
POSITIONPOINTER AT CENTER
OF DIALMARKING 68
L
L
-
CORD LEGEND^
CORD-
CORD -
AM DIAL
FM DIAL
— L •
— L •
36_V
34V
Figure 9. Dial Cord Stringing Instructions
-10-

PARTSLIST
SYM-
BOL
C2
C12
El
E2
E3
E4
Jl
J2
J3
J4
J5
J6
J7
J8
J9
L2
L3
L4
L7
L8
L9
L10
L15
L20
L23
PI
R30
DESCRIPTION
Variable, 4 sections
Variable, 3 sections
PrintedCircuit, IF
PrintedCircuit
Dummy Panel
Terminal Panel, antenna
Phono-jack, dbl, Cinchtype8113
Phono-jack, dbl,Cinch type 8113
Phono-jack, single, Cinch 8171
Receptacle, A.C., CordstypeCC-2
Jack, 16 contacts, Amphenol 26-
4200- 16S modified
Receptacle,A.C., Alden 402ACE
Receptacle,A.C.Alden 402ACE
Phono-jack, dbl,Cinchtype8113
Phono-jack, dbl,Cinchtype8113
R.F.Coil
R.F.Coil
R.F.Coil
R.F. Coil
R.F.Coil
Choke, R.F., 2 uh
Choke, R.F., 100uh
Choke, R.F., 100uh
Choke, R.F., 100uh
Choke, R.F., 2 uh
Dummy Plug
Variable,100,000ohms log taper,
NAT. CO.
PART NO.
T442-1
T441-1
T605-1
T606-1
T671-2
T454-2
T579-1
T579-1
T458-1
L283-1
T448-1
T452-1
T452-1
T579-1
T579-1
T618-1
T619-1
T617-1
T566-1
T567-1
SB:2602
SA:3003
SA:3003
SA:3003
SB: 2602
SB:2800
T578-2
SYM-
BOL
R58
R72
RC1
SU1
Tl
T2
T3
T4
T5
T6
T7
T8
T9
Wl
XF1
Yl
Zl
Z2
Z3
DESCRIPTION
with SPST switch IRC type Q
Variable,500,000 ohms, A taper
Clarostattype 47
Variable,1,000ohms, A taper, IRC
type RQ11-108
Diode Filter
Rotary switch, 8 pole, 4 position,
Grigs by- Allison type 4MLW
Antenna Coil, includesL6A, L6B
IF Transformer
IF Transformer
IF Transformer
IF Transformer
IF Transformer
IF Transformer
IF Transformer
Power Transformer, pri117 VAC,
60 cycles; sec 300-0-300 v at110
ma DC,5 v at2 amps, 6.3v at5
amps and6.3v at1amp
Power Cord, AC, Cords 18/2POSJ-
64
Fuseholder Littlefuse type34201
Germanium Diodetype1N60
CoilAssembly
Coil Assembly
Coil Assembly
>JAT. CO.
3ART
NO.
TO 13-7
T013-8
T604-1
T453-1
T565-1
T608-1
T608-7
T608-2
T608-8
T608-3
T608-9
T608-4
T580-1
L284-1
E510-1
T614-1
T608-6
T609-1
T608-5
CONDITIONS
Selector Switch
VTVM used for
117 VAC, 60cy
No input signal,
Tolerance ±10%
PIN
TUBE
VI
V2
V3
V4
V5
V6
V7
V8
V9
V10
Vll
V12
V13
V14
1
200
0
-0.7* •
-8to-10
-0.5"
-0.5**
-0.5**
-0.5**
190
-0.7
-0.7
0
190
117AC
:
110
-2t
1.71
0
0
0
0
0
n
0
0
-8
120
*
*5 VAC across pinj
"Tolerance ±20%. i
Figure 10. Functional Block Diagram
-11-

TABLE 1. TUBE SOCKET VOLTAGES
P.M. R.F. SECTION
at FM.
ill measurements.
:le input.
unlessotherwise noted, all readings DC except as noted.
-4
3
110
75
0
0
0
0
6.3AC
0
12
0
0
6.3AC
20
120
200
4
6.3AC
6.3AC
6.3AC
6.3AC
6.3AC
6.3AC
0
5. 5 AC
0
6.3AC
6.3AC
20
0
300AC
5
0
0
170
200
210
210
210
-0.5 to -0.7
0
100
100
-4 to-7
0
20
6
110
0
100
70
100
100
100
-0.7 to1.0
140
5 to7
5 to7
0
120
300AC
7
-0.5**
•1.5 to-3
1.7**
-0.7**
0
0
0
30**
-0.5
190
190
-4 to-7
0
117AC
8
0.8**
90
—
—
—
—
—
—
1
—
—
«_
1
*
9
—
200
—
—
—
—
—
—
6. 3 AC
—
—
—
6.3AC
— —
2 and8.350 volts D.C. to ground.

•&{ «-AAAr-f—|C47 I2AX7
VI I
470K
=$= AUDIO AMPLIFIER-
IN60T. -=il00 CATHODE FOLLOWER
NOTE-
CAPACITOR VALUES«MICROMlCROFAf)ADS EXCEPT AS NOTED
RESISTOR VALUES-OHMS
K- 1000
M • MEGOHM
CAPACITORS 500 VOLTS WORKING EXCEPT AS NOTED
OHMIC VALUE OF FIXEDRESISTORS i lOX EXCEPT AS NOTED
FIXED RES
Figure 77. Schematic Diagram

3.FMRF ALIGNMENT
Correct alignment oftheFMRF sectionrequires the
useofa signalgeneratorcapable of covering the
range of87to109 megacycles. A typicalunit isthe
Boonton 202A. In addition, a DC vacuum tube volt-
meter is required andan insulatedalignmenttool with
a narrow screwdriverblade. Ifthe calibration ofthe
generator isatall questionable itis suggested that
an FM broadcaststation at each endofthe dial be
used asa frequency standard.Proceed as follows:
Step 1. Connect the signalgenerator totheFM
antenna terminals. Setthe frequency at109 me. and
setthe tunerdial atthe same frequency.
Step 2. Connect the VTVM attheFMAGC line
(test point no.2).
Step 3. Adjust oscillator trimmer C2Hto produce
maximum AGC voltage,reducing the generatoroutput
as necessary.
Step 4. Adjust mixer trimmer C2Ffor maximum
AGC, rocking the generator frequency slightly to
insure optimum tuning.
Step 5. Repeat step 4, adjusting C2Dand C2B.
Step 6.Setthe generator frequency and tuner FM
dial at 87.5 me.
Step 7. Obtain maximum AGC voltage by adjustment
of L4,L3,L2and LI. Theair wound coils aread-
justed by veryslightlycompressing or separating
the turns.
Step 8. Repeat the entire process (steps 4 through
7) until no further adjustment is required at either
endofthe dial. During this entireprocedure, make
certain that the generatoroutput is- justhighenough
to produce a usable AGC voltage.Disconnect the
test equipment.
4.AMRF ALIGNMENT
For alignment oftheAM front end, a standard sig-
nal generatorcovering the broadcastband(500 to
1650kc.) is required. The procedure is straightfor-
ward and conforms to standard service techniques.
Step 1. Connect the signal generator atthe AM an-
tenna terminals. Setthe frequency ofthe generator
and tuner at 1650 kcs.
Step 2. Connect the VTVM attheAMAGC line,
test point no.4, (junction ofRC1and R29).
Step 3. Adjust oscillator trimmer C12F to obtain
AGC voltage.
Step 4. Adjustmixer and antennatrimmersC12D
and C12B for maximum meter reading.
Step 5. Disconnect all test equipment.
5. ADJUSTMENT OFHUM BALANCE RESISTOR
Thehum balance resistor R72is factoryadjusted
for properoperation and these instructionsshould be
carried out only ifthe resistor setting is inadvertent-
ly disturbed orthe control replaced.
a.Ifthe tuner is usedwithout the preamp setthe
selector switch atFM. Disconnect theFM antenna.
Turn theFM volumecontrol on full and adjust R72
for minimum audible humas heard from the speaker
system.
b.Ifthe Horizon 5 preamp is used with die tuner
setthe Selector ofthe preamp atanyofthe7 Phono
Compensation positions. Setthe Loudness control
full onand adjust R72for minimum hum.
6. MUTAMATIC ADJUSTMENT
This control is factoryadjusted for normalsquelch
threshold level. If readjustment is desired turn the
control(R58) fully counterclockwise. Setthe Se-
lector ofthe tuner atFM Mutamatic andsetthe tuning
dial ata point where only noise is heard.Turn R58
in a clockwisedirectionuntil the background noise
just disappears. Turn the controlabout 5 degrees
further inthe clockwise direction. The Mutamatic
is now properly set and will "pull-in" on all but the
weaker signals, yet block out annoying inter-station
noise.
Standard Form Warranty
Adopted by the Radio Manufacturers Association, Inc.
This equipment is warranted tobe free from defective material and workmanship and repair or replacement
will be made ofany part which under normal installation, useand service discloses defect,provided rhe unit
is delivered bythe ownet tothe manufacturer of through the authorizedradiodealer or wholesaler from whom
purchased,intact, for examination, with all transportation chargesprepaid to the factory, withinninetydays
from the date of sale to original purchaser, and provided rhat suchexamination discloses in the manufacturer's
judgment that itis thusdefective.
This warranty does not extend toany radioproducts which havebeen subjected to misuse, neglect,
accident, incorrect wiring, improper installation, ortousein violation of instructionsfurnished by the man-
ufacturer, nor extend to units which havebeenrepaired or altered outside ofrhe factory, norto cases where
the serial number thereof has been removed, defaced or changed, dor to accessories used rherewtfa of other
manufacture.
Any parr ofa unitapproved for remedy or exchange hereunder will be remedied or exchanged by the
authorizedradiodealer or wholesaler without charge tothe owner,
this warranty isin lieu ofall otherwarranties expressed « implied andno representative or person is
authotized to assume forthe manufacturer any otherliability in connection with the sale of theirradio products.
National Company,Inc. reserves the right to make any change in design orto make addition to, or im-
provements in, |itsproducts without imposing any obligations uponitself to install them inits productspre-
viously manufacrurered. *
-12-
AC-3000-ER394