Heathkit SP 2A Assembly Operation

Page 1

PRICE $3.00

Assembling

and Using Your. . .

MONAURAL-STEREO
HIGH FIDELITY
PREAMPLIFIER

MODEL SP-2A

HEATH COMPANY

A Subsidiary of Daysnom Inc.

BENTON HARBOR, MICHIGAN

595- 296

Copycigm 1959
Hnavh Com pany

Page 2

STANDARD COLOR CODE - RESISTORS AND CAPACITORS

INSULATED FIRST RING SECOND RING TIIIIRD RING
nl LEAD RBISIOR UNINSULATIID BODY COLOR END COLOR DOT COLOR
Inna-lowland Color First Figure Second Figure Multiplier . DISC CERAMIC RMA (ODE
Rhtl- Rubi-saluted BLACK 0 0 None 5-0 (I I 3-D
.= § Q Elli 5 l» 03 P" "
§ § =' OIlANGE 3 3 000 Multipllu
s YELLOW 4 4 0mm Tolomu
L Tehran GREEN 5 5 00,000
333a. 3 3 3333
hi all 1nd Slwfimfl Nauru . I C II.
Wire wound Iulslou have $912?qu 3 3 Ogggggggg M- u
in am in; Jun. «tat ~ .
RADIAL lEAD DOT RESISTOR SDOT RADIAL [EAD CERAMIC CAPACITOR EXTENDED RANGE TC CERAMIC NICAP
M ltl l (
\\u Pl" %/ "a R invinu. 1 openly Ll
\ /. 2.4 (all.
I; \\ \aé Item §\
J l ' M lilo? Toleran-
I- not I" "E". . m, K multiplier Moltlplln Talon-Kc
RADIAL LEAD (BAND) RESISTOR DY-PASS COUPLING CERAMIC CAPACITOR AXIAL LEAD CERAMIC CAPACITOR
(cruelty
mtnultu
, IV- - w"... haw Cool. _j (spoon
V 7nd Ngu- {Opt} §
Multipliu Talon." M'Ifi'II" Toll!!!"
Talon-n l" fig-r.

The. standard color code provides all necessary information re-
quired to properly identify color coded resistors and capacitors.
Refer to the color code for numerical values and the zeroes or
multipliers assigned to the colors used. A fourth color band on
resistors determines tolerance rating as follows: Cold = 5%.
silver = 10%. Absence of the fourth band indicates a 20%
tolerance rating.

The physical size of carbon resistors is determined by their
wattage rating. Carbon resistors most commonly used in [leath-
kits are 1/3 watt. Higher wattage rated resistors when specified
are progressively larger in physical size. Small wire wound
resistors 1/2 watt. 1 or 2 watt may he color coded but the first
band will be double width.

MOLDED MICA TYPE CAPACITORS

CURRENT STANDARD CODE

RATED 500 W.V.D.C. t 20% T01.

RMA 3-DOT (OBSOLETE)

BOTTOM SILVIR MICA

In nd i Sig-firm fi'm

-:::;H.D Volt-go - nultlpllu
=-
F- hlcrua World-g ®--- Isl-"mo

Voltage ltalk

n t . (motor 0
We. (am) gala l""" "9'" #3 T n M n a." :1
"wk (Ill "- WWII" M - . P u blew-(o I \ bl"
(00! it
(In; Tel-mu 2:: £31,"; (at "gm MdllPIlfljld a. ml 05:":
RM (500! 0350M! <00!) am we! (ossotm) am 4-001 (035mm)
1" w m - no
1.6 l Sig-Ilium "gun 7"? =-® ® Talon-u 2d}$ignlfiran "an Working Voltage
Molflpllu Illtlpllor 3,;
® hut

® II-Ittyllu ® - Inltlpllov

I 'II. 2" % $ 6 ' n
-'Wuklng Volt. - m N no pm

MOLDED PAPER TYPE CAPACITORS

mum CAPACITOR "'liWfiM n...
MuleII-r
Manually
- = WP I"
== = val
Toleran- hd gift",
ml mm Hum

A 2 dlflt voltage rating 3.6mm run that 900 V.
Addilmstondd2dlgltmlnr.

MOLDED FLAT CAPACITOR JAN. CODE CAPACITOR
Cumudd («In V! 1 Silver In; SiIIDtI-t
o I: Volt: 2 "gm.
II-dt w
..., W
- Multipllu § $ ®- Multiplier
fizsmmmngm Wm'mkl- Vol-rm-

The tolerance rating of capacitors is determined by the color
code. For example: red = 2%. green = 5%. etc. The voltage
rating of capacitors is obtained by multiplying the color value
by 100. For example: orange 2 3 X 100 or 300 volts. Blue =
6 X 100 or 600 volts.

In the design of Heathkits. the temperature coefficient of ceramic
or mica capacitors is not generally a critical factor and there.
fore Heathkit manuals avoid reference to temperature coeffi-

cicnt specifications.
Cou'tuy of Conunlcbr

Page 11

"Level" Controls ....................
"Loudness" Controls .................
"Auxiliary" Level Controls. . . ........
"Mag Phono Level Controls ..........
"Output" Level Control ...............

"Hum Balance" Control ..............

MAXimum

off
MAXimum

6MV sensitivity position
MAXimum

optimum; for particular selector switch
setting

In accordance with good engineering practice a list of the test equipment used in making the
specification measurements for the SP -2 Monaural Stereo Preamplifier is given below:

AC Voltage Metering ................

Generators .........................

Distortion ...........................

Oscilloscope .................... . . .

Line Voltage Control .................

Hewlett Packard Model 400 D
Vacuum Tube Voltmeter

Heathkit Model AV -3 Vacuum Tube Voltmeter
Krohn-Hite Model 440 -A Test Oscillator

Hewlett Packard Model 650 A
Test Oscillator

Heathkit Model AG-lO Sine -Square Generator

Hewlett Packard Model 330 B
Harmonic Distortion Meter

Heathkit Model AA-l Intermodulation
Distortion Meter

Tektronix Type 515 Oscilloscope

General Radio Co. Type W5MT Variac

Beckman Instruments, Inc. Model 6R115C10A
A. C. Voltmeter

Page 9

Page 27

with the arrow screened on the circuit board. Be sure that each socket contact is in line
with a hole in the board before pushing it through. Carefully solder each contact (including
center pin ) to the adjacent pattern. Do not attempt to cut off the tip of the contact before
or after soldering.

( ) Follow the wiring sequence diagrams (Pictorial 3) and check off each step when completed
so that no parts or jumpers are omitted. Please note that the 31 steps on Pictorial 3 must
be completed before proceeding with the next step. Solder all connections and clip off ex-
cess leads.

This completes the preliminary assembly of the circuit board.
FINAL ASSEMBLY AND WIRING

( ) Mount the circuit board just completed on the chassis using a 3-48 screw, nut, and #3 lock-
washer in each of the four small mounting holes as shown in Pictorial 4 on Page 26. Mount
lockwasher and nut on top of Printed Circuit Board. The board must be positioned as shown,
with the 25 aid 25 volt electrolytic capacitor to your right. It may be necessary to loosen
the nut on control J in order to mount the circuit board more easily.

( ) Cut a 21 1/ 2" length of 8 conductor cable. Remove the outer jacket to expose 7 of the inner
conductors (see Detail 7). This can be done by slitting the jacket with a sharp knife for a
«length of 7" and then peeling the jacket off by pulling with a pair of pliers.

( ) Prepare the exposed conductors by cutting each lead to the following lengths:

Yellow 1 1/2" White .. .. 2" Green . . . . 3 3/4" Brown 7"
Orange . . .. 1 1/2" Black .. . . 3 3/4" Red ...... 6 1/2" Blue ...... Cut this lead off
at the insulation (not used).

Strip about 1/ 4" of insulation from all but the blue lead.

( ) At the other end of the 8 conductor cable, slip the vinyl plug cover over the cable, with its
open end toward the unstripped end of the cable. Remove about 3/ 4" of the outer jacket
from the cable. Cut off the blue lead at the jacket and strip the remaining 7 conductors to
expose about 1/4" of bare wire (see Detail 7). Tin the exposed bare wires.

( ) Identify the molded 9 pin connector and note that the pins are numbered on the eyelet side of
the plug. Follow the numbering on the plug and connect the 3/ 4" exposed wires as follows:
See Detail 7. . -

Orange to pin 3. Brown to pin 5. Black to pin 7. White to pin 9.
Yellow to pin 4. Red to pin 6. Green to pin 8. Blue is not used.

( ) Solder each wire firmly to the eyelet. See that none of the pins are shorted together by
excess solder or an adjacent lead. After all the connections are properly made, slip the
cap over the plug.

To PIN' 3056

ACTUAL LENGTHS
33

BLCK

Detail 7 Page 25

Page 30

PICTORIAL 6

Refer to Pictorial 6.
( ) Connect a hookup wire from 51 (NS) to S4 (NS).

( ) Locate the twisted pair of wires extending from GC4. Connect the lead that has the insulation
removed to SS (NS).

( ) Remove approximately 1/ 4" of insulation from the remaining lead at this end of this pair
and connect to M3 (S-3).

( ) Connect the bare wire (use sleeving) extending from GB12 to M2 (S-l). Do not allow this
lead to pass in front of the hollow shaft; position as shown.

( ) Connect the 1 megohm (brown -black-green) resistor extending from GC3 to S4 (NS). Use
sleeving.

( ) Solder the pigtail from the shielded cable that is connected to GD? to the bare wire between

control terminals L3 and M3.

( ) Locate the twisted pair of wires extending from GCZ. Connectthe lead that has the insulation
removed to 83 (NS).

) Remove the insulation from the remaining lead in this pair and connect to L3 (NS).

(
( ) Connect a 100 K ohm (brown -black-yellow) resistor from S5 (S -2) to S4 (NS).
( ) Connect a 47 K ohm (yellow-violet-orange) resistor from S4 (S -4) to SS (S -2).
(

) Connect a bare wire from L3 (S-3) to 81 (NS).
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Page 34

PICTORIAL 8

( ) Connect the bare wire at the end without pigtail to E2 (S-Z). Connect the other end of the

bare wire to C814 (NS) on the circuit board. Now secure the pigtail to C1 (NS). Check the
position of the spiral shield and position it sothat it cannot toucheither the chassis orother
wiring, also see that a short does not exist between the spiral shield and bare wire.

( ) Connect a 3 1/2" length of hookup wire from C315 (NS) to B2(S-1). Dress this lead against

the circuit board.

Installation of the Loudness Control Network.

(

(

) Identify the encapsulated loudness control network, part number 84-9. This unit has four

leads extending from one side.

Install the network on the rear of the loudness control B as shown in Pictorial 8. Note the
position of all four leads. Pass lead four through Bl (NS) to C1 (NS). Use sleeving between
terminals B1 and C1 as shown. Now solder B1 (S-l).

Pass lead one through B3 (NS) to C2(S-l). Use sleeving between B3 and C2. Now solder BB.

Position the body of the network at a. right angle with the control as shown. Place sleeving
over lead number three and connect to BS (S-l).

Place sleeving over lead number two and connect to B4 (S-l). Position the lead as shown.
The body of the network must not rest against the rear of the control and cover the opening
on the hollow shaft.

) Connect a 6" length of hookup wire from C816 (NS) to P3 (NS). Dress the lead as shown.

Page 3 2

Page 48

(

A

(
(

)
l

l
)

PICTORIAL 7

Cut leads 1 and 8 to 3/4" lengths.

Cut lead number 4 to 1/4" and connect a 6 1/4" length of bare wire to it as shown. Solder
the connection securely.

Slip a 5 3/4" length of sleeving over the bare wire just connected to lead 4 on the network.

Cut a 5" length of spiral shielding and unwind about 2 1/2" of the wire at one end and then
place a 5 1/4" length of clear plastic tubing over the spiral shield.

Now slip the spiral shield with tubing over the bare wire and sleeving extending from lead
4 on the network, with the pigtail on the free end of the bare wire.

Refer to Pictorial 7 and install the network on the rear of controls EE and FF. Connect
lead number 1 to EE3 (S-l). Position the shielded wire coming from lead 4 between the
network and apron. Position the network exactly as shown.

Connect lead number 8 to PM (8-1).

Connect lead number 7 to JJ3 (8-3). Use sleeving.

Connect lead number 6 to EEl (S-l). Use sleeving.

Connect lead number 5 to EEZ (NS). Use sleeving.

Connect lead number 4 (shielded hookup wire) to CBll (NS) on the circuit board.

Connect the pigtail from the shielded cable to control terminal CCl (NS).

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Assembly of Remote Stereo-Balance Control. Refer to Pictorial 9.

( ) Prepare both ends of the 20 foot length of three-wire shielded cable as shown in Pictorial 9.
Atone end remove about 3/4 of the outer jacket and then unwind the exposed portion of the
woven shield. Cut the shield off at the jacket and remove about 1/4" of the insulation from
each end of the three inner wires. Tin each of the three leads.

( ) At the other end remove about 1" of the outer plastic jacket. Unwind the woven shield and
twist to form a pigtail, or fourth lead. Strip 1/2" of insulation from the threeinner conduc-
tors. Tin the three leads and the pigtail.

( ) Place the connector cover over the end of the cable that has the pigtail. Note that each pin
on the four-pin plug has been identified with a number on Pictorial 9. The identification is
made from the TOP VIEW on the side without the pins. Starting from the large space, or
key and counting counterclockwise, make the following connections:

NOTE: When inserting the leads through the pins, insert them far enough so that about 1/4"
of bare wire extends beyond the pin, then bend the wire so that it will not slip out.

White to pin 1. Pigtail to pin 3.
Red to pin 2. Black to pin 4.

( ) Solder the wire in each pin by heating the tip of the pin with the soldering iron and letting
the solder flow inside; see that no excess solder sticks to the outside of the pin. If neces-
sary, reheat the pin and wipe off the excess solder with a cloth. Cut off the bent-over
portion of wire, and smooth the end of the pin with an emery board, sandpaper or a small
file.

( ) Press the cap over the plug and bend the four lugs over and secure the cap to the plug.
Refer to Pictorial 9.

( ) Identify the rubber control housing and slip it over the end of the cable without pigtail. Tie
a knot in this end of the cable, very close to the end.

( ) Identify the 100 K ohm miniature control RC and make the following connections. When
handling this control, do notexert strain on the solder lugs, as this is a miniature type con-
trol and is very delicate.

( ) Connect the white lead to terminal RC1 (S-l).

( ) Connect the red lead to terminal RC2 (S-l).

( ) Connect the black lead to terminal RC3 (S-l).

( ) Place the miniature control lockwasher on the control bushing, then place the flat panel
washer with the blank side against the lockwasher. Temporarily secure the lockwasher and
panel washer with a 1/4-32 control nut. Do not tighten yet. Now turn the control to the

extreme clockwise pesition.

( ) Locate the remaining small black knob and install on the miniature control shait, and align
the pointerwith the last position on the panel washer in a clockwise direction by rotatingthe
control. When the pointer is aligned, tighten the control nut and replace the knob.

( ) Carefully pull the cord thrOugh the handle until the washer rests against the front of the

handle. Insert the washer into the slot provided on the inner rim of the cone. This com-
pletes the assembly of the Remote Stereo Balance control.

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