Heathkit FM 3A Manual

Page 1

PRICE $1.00

Assembling

and Using Your. ..

; H e

' FREQUENCY ,
MODULATION
TUNER '

MODEL FM-3A

I-IEA'I'H- COMPANY

A Subsidiary of Daysrrom Inc.

BENTON HARBOR, MICHIGAN

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STANDARD coion CODE -- - RESISTORS IAND CAPACITORSI

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ASSEMBLY ANDOPERATION OF THE

___________ INSULATED FIRST RING SECoND nING I THIRD RING, I
AXIAL mm mum " H E AT H K I T M O D E L F M - 3 A
Brownqmlmd . Golor Firlelgure Second Figure lVIulliplier DISC CERAMIC MA CODE ,
lllurk- Nan-insululed I ' I 5-00! 3-Dol
BLACK 0 0 None .
FRgWN 1 1 0 p, (uuurliy i FREQUENCY MODULATION TUNER
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- =' ORANGE 3 3 ,000 \ MulIIpIIer
YELLOW 1L 4 0 000 Tolerance
I- Tolerume GREEN 5 5 00 000
Multiplier gllglfilT 6 g 0 000 000
Isl and 2nd Signifimnl Figures I . 7 5000:000 T . C R.
ennui resislors have 4 SilIfiAIgF g 3 038%83888 amp I
hand dnuble wiIlllI . 4 I I
RADIAL LEAD DOT RESISTOR I 5-DOT RADIAL. LEAD CERAMIC CAPACITOR EXTENDED RANGE TC CERAMIC l'llCAP
Multiplier ' - Temp. (m I (upurily

l I' Toleiunre :
e "9" M"""'" K Multiplier Mulliplier Inlemme
RADIAL IEAD (BAND) RESISTOR BY-PASS COUPLING CERAMIC CAPACITOR AXIAL LEAD CERAMIC CAPACITOR
. . (upucilv
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(0.11.) m£§

Muliiplier ~--I Tolsrunte

2nd Figure

Mulliplier Tolerunw

clemnce 15' Figure

standard color code provides all necessary information re- The physical size of carbon resistors is determined by their
ed to properly identify color coded resistors and capacitors. wattage rating. Carbon resistors most commonly used in Hea th-
31' to the color code for numerical values and the zeroes or kits are 1A watt. Higher wattage rated resistors when specified
tipliers assigned to the colors used. A fourth color band 011 are progressively larger in physical size. Small wire wound
Itors determines tolerance rating as follows: Gold = 5%, resistors 1/2 watt, 1 or 2 watt may he color coded but the first .

= 10%. Absence of the fourth band indicates a 20% hand will be double width. I

ancel'ati'1g' MOLDED MICA TYPE CAPACITORS

CURRENT STANDARD CODE RMA 3-DOT (OBSOLETE) BUTTON SILVER MICA

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CODE .
(luss Tolerunle 2" s'Esignilimni Figure MultIplIeranl digit ml Digil I
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_ Signifimnl Figure Workmg \\\\\ ® 70'9? 5' . . . I
M . v I. _ , _ 2 d s r IF .
@ MulIiplier 0. 99 \\\\l \\\V ® Multiplier arid mm a" Igures \\\ WorkIIIg Voltage .
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AR CAPACITOR. 2m dlfiignllrnnifigure, MOLD: FLAT CAPACITOR JAN. CODE CAPACngR Signifimnr J
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,-- MVIIIPIIW ~ . - Workmg VolIs . 2nd Flgure
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I?§..I"JI"2'3IJ.I"$..T§K " IsIIs'g"'"""'° (hurt-"em": I

tolerance rating of oapacitois is determined by the 09101 I III the designof Heathkits,-theiempemture coefficient of ceramic
F01 example: redw - .200, green - 5%, etc. The. voltage Nor mica capacitors is not generally a critiéal factor and there-
g of capacitors is obtained by multiplying the color value fore 'l-Teathkit InaIIIIalsfavoid reference to temperature (zoom,
)0. For exanipl ' range = -3 X 100 or .300 volts. Blue = cien'tspecifications. -
[00 01 600 volts. . ,. : . . . . . . . » _ Cowlesx oI Conltalub
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PICTORIAL 1

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LINE CORD

LEADS

. TRANSFORMER

PICTORIAL 2

STEP-BY-STE P WIRING INSTR UC TIONS

(V) Bend the four mounting frame tabs on sockets B and C back over to chassis since they will
not be used.

(V) Connect a short piece of bare wire from tube socket A3 (NS) to the center post A8 (NS).

(11/) Connect a short piece of bare wire from tube socket B4 (NS) through the center post 810 (NS)
and lug B9 (NS) to ground lug B11 (NS). Wrap the wire around the ground lug near to the
chassis to make room for other components which will be added later. Now solder B9 (1)

and B10 (1). Note that the center post can be rotated with pliers if necessary to line up the
holes.

NOTE: Good solder connections are essential if stable and reliable performance is to be ob-
tained. If not thoroughly familiar with good soldering technique, it is recommended that the
paragraphs under the heading PROPER SOLDERING PROCEDURE be reviewed at this time.

Careful attention to soldering procedure may save considerable trouble shooting time upon com-
pletion of the tuner.

(V) Dress the .001 )lfd disc condenser connected to the tuning assembly P5 under the oscillator
coil as shown in Pictorial 1 and cut the free end to a length sufficient to reach C1. Connect
this free end to socket Cl (NS) (use sleeving). Dress tight to chassis, making sure none of

the wires short to ground. Take care not to abuse the coils on the tuning assembly or the,
calibration may be disturbed.

(V) Connect the bare wire from tuning assembly ground lug P5 to socket ground lug 011 (NS).
Secure close to chassis and make sure the wire does not touch the tuning coil at any point.

(13/) Run a short bare wire from socket'ground lug C11/(NS) through center postClO (NS), through
lug 05 (NS) to ground lug 012 (NS). Now solder C5 (1).

(1,») Connect a short bare wire from socket D4 (NS) through center post D8 (NS), through D7 (NS)
to ground lug D9 (NS). Now solder D8 (1).

(V) In the same manner, connect a short bare wire from socket E4 (NS) through center post E8
(NS) and pin E7 (NS) to ground lug E9 (NS). Now solder E8 (1). l

(1/) Connect a short bare wire from socket F3 (NS) through center post F8 (NS) to ground lug F9
_ (NS). Now solder F3 (1) and F9 (1). v
(V) Run a bare wire from socket F6 (S) (1) to center post F8 (S) (2). Make sure'the solder flows
over all wires connected to F8.

(L/) Connect a bare wire from socket G3 (NS) through center post G8 (NS) to ground lug GE) (NS).
Now solder G3 (1) and G8 (1).

Before continuing the wiring, check all sockets to see that none of the bare wires are touching
any contacts other than those to which they are attached. If wires are close to contacts, bend
them away slightly to avoid the possibility of short circuits.

(3/) Connect an insulated wire from socket center post A8 (S) (2) to socket B4 (NS). ' .

(if) Run a wire from sOcket A4 (NS) to socket B5 (NS). Dress tight to chassis near sockets as
shown. ,

(V) Connect a wire from socket B5 (NS) to socket D3 (NS). Dress the wire tight to chassis be-
hind terminal strip S and between IF transformer W and socket D.

(V) Connect a wire from socket B5 (S) (3) to socket G4 (S) (1).

(17) Run a wire from socket D3'(NS) to socket E3 (NS).

(if) Route a wire from socket E3 (S) (2) to socket F4 (S) (1). Dress the wire between socket E
and transformer X. Be sure it is tight to chassis.

This completes the filament wiring for all tubes except the 6U8 socket C, and the pilot lamp .,
These, Will be wired later. '

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Page 16

Alignment of the tuning assembly should not be attempted unless there is conclusive evidence of
misalignment. Since most signal generators do not cover the frequency range of 88 to 108 mega-
cycles, it will probably be necessary to use FM stations of known frequency as a signal source.
An antenna should be connected to the antenna terminals or if a high frequency signal generator
is available, connect the output to the antenna terminals. 'Connect a voltmeter to ground and
terminal strip TTl as before. Tune in a station near 106 me or set the signal generator and
tuner dial to 106 mc and carefully adjust the RF trimmer (nearest the dial drum) for maximum
indication on the meter. Adjust very slowly, for the adjustment is critical. Rock the dial back
and forth while adjusting the trimmer in order to find the highest peak response. The oscillator
trimmer, nearest the chassis, should not be touched unless the calibration is off badly. If this
should be the case, tune to a station known to be near 106 mc.~ Turn the tuning knob to set the
pointer to a point nearer the proper frequency mark on the~dial, but keep the signal tuned inwell
enough to cause an indication on the meter. Carefully adjust the oscillator trimmer for maxi-
mum indication and repeat the procedure until proper frequency calibration is obtained. The
same procedure should be observed if a signal generator is used. After oscillator adjustments
are completed, the RF trimmer should be readjusted as described above. Alignment of the
FM-3A Tuner is now complete.

FINAL ASSEMBLY OF THE TUNER

Figure 20

( ) Place the panel reinforcing bracket over the stud at the center of the front panel, as shown
in Figure 20. The stud goes through the bracket, a large 9/16" flat metal washer, a lock-
washer and nut. Tighten in place with the bracket flange slightly below and parallel with

the top of the panel. Note: Avoid bending the front panel during construction and installa-

tion of the tuner, for the glass will crackunder excessive strain.

(I/)' Mount the HEATHKIT nameplate on the front panel. Insert the pins through the small holes
in the upper left corner of the panel. Push a spring steel speednut down over each pin from
the back of the panel. The long side of each speednut must be parallel with the top of the
panel. Cut off excess length of each pin.

( ) Make sure the tuner is disconnected from the power outlet and_remove the nut holding the
volume control in place on the right bracket. Hold the control firmly in place and slip the
right hand opening in the panel over the control shaft. Place the control flat washer over
the shaft and secure with the nut. Do not tighten yet.

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( ) At the left end, secure the panel with a 6-32 self-tapping screw
through each elongated hole in the front panel bracket, after lining
these holes up with the ones in the left chassis bracket. Leave the
screws slightly loose.

( ) Bend both pilot lamp brackets forward until the bulbs almost touch
the front panel.

( ) Observe Figure 21 and install the four rubber feet in the four large

, holes provided in the bottom cover. Insert from the painted side of Figure 21
the cover.
9 ( ) With the cooling vents to the rear, install the bottom cover as shown in Figure 22, using

6-32 self-tapping screws at each dimpled opening.

CABINET SHELL

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Figure 22 é &

( ) Align the bottom coverso that the bottom ed '
' ge is Just flush With the bottom edge of the anel
and tighten the control nut and the self-tapping screws at the left end. Inspect the asselznbly

f1 0111 the top to make SL118 110118 of the electrical components 01111th 011 the (31135815 3.19
m

( ) Slip the knobs on the control shafts The knobs
. . push on the flatted shafts after ro er
alignment between the flat and the spring insert in the knob. If necessary, loosen tlfe £1-

ume control nut to secure proper relationship between the knob d' ' '
markings. Then retighten the nut. 1n mator 11116 and the panel

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