Heath Heathkit W4-AM Assembling And Using

PRICE

$1.00

WILLIAMSON TYPE

AMPLIFIER

MODEL W4-AM

HEATHKIT

WILLIAMSON-TYPE

AMPLIFIER

MODEL W4-AM

Phase Shift:

Intermodulation Distortion: See curve

below.

Sensitivity:

See curve below.

EQUIVALENT SINGLE

FREQUENCY

PQWER

Hum and Noise: 76.2 db below 0.25 watts

output.

95.2 db below 20 watts

output.

Feedback Factor:

Fixed; 22.6 db; independent

of output impedance.

Damping

Factor: Fixed;

28.5

to

1;

independent of output

impedance.

Output Impedances;

4, 8,

and 16 ohms.

Input Requirements:

105-125

volts,

50-60

cycles

AC,

115 watts at 117 volts.

Dimensions;

Single

unit;

15

1/4"

x

8

7/8" shelf

space,

7"

high.

Allow 1

1/2"

X

IS

1/4"

additional shelf space

for cables

and connections.

Weight:

Net: 23

1/4

lbs.

Shipping: 28 lbs.

TEST

CONDITIONS

Measurements taken at 117 volts line, with

WA-P2

preamplifier

connected.

Output

impedance

16.02 n resistive. For

harmonic distortion measurements; Krohn-Hite model

440-A

generator

(inherent distortion less than

0.1%),

Hewlett-Packard

330-B

distortion analyzer. For inter-

modulation distortion measurements; Measurements Corporation model 31 intermodulation

meter. For frequency response measurement,

Hewlett-Packard

model

650-A

test oscillator

.

For phase shift measurements, same oscillator with Tektronix 531 oscilloscope with

53-C

pre-

amplifier.

For

output

power,

voltage

measurements across

16.02

D

resistive

load,

taken

with

Hewlett-Packard model

400-D

vacuum tube voltmeter.

Measurements given are those taken on

a

representative amplifier under conditions stated.

Minor variations

from

these figures may be encountered in kit-assembled amplifiers because of

tube characteristics, component variations and

exact

lead placement. In

a

highly stabilized

amplifier such as the W-4AM, these variables may

be

disregarded from a performance point of

Page 3

INTRODUCTION

Most people are inclined to view the meteoric rise of the high

fidelity craze

as something which

has taken place in the last two years. Actually, public

acceptance of

home music reproduction

probably dates

from

the

summer and fall of 1948 when the Columbia "LP"

microgroove record-

ing techniques were introduced.

It is significant that a year earlier, there was

described in the British

publication "Wireless

World," an

amplifier

circuit

designed

by Mr.

D.

T.N.

Williamson which

culminated an extensive

search for what the author described as

a

perfect amplifier.

Within two years, the audio

world

had so

completely accepted the circuit that

it

became

a

standard for

comparison. After eight

years, the design still accounts for

by

far the greater percentage of

all high fidelity power am-

plifiers in use today.

Improvements have been

made,

faults have been discovered and corrected,

other circuits have

challenged the Williamson's

position,

but

still it stands as the basic high fidelity

amplifier.

Truly, the audio field owes Mr. Williamson

a

great debt.

In the

past

four years, literally

thousands of

people

have built and used Heathkit

Williamson-type

amplifiers. They represent a large majority of the

units of this type now in use

throughout the

audio-conscious

world. Your Heathkit model W-4AM Amplifier

incorporates all the

worthwhile

improvements and modifications resulting

from

this unequalled background.

If you are technically inclined, the

information contained in the preceding specifications will have

satisfied your questions as to the measured performance of the

amplifier.

If

you are

interested

primarily in how the amplifier will sound

,

your Heathkit W-4AMis

capable of placing the

burden

of proof on the most

elaborate and expensive speaker systems available today.

Unless you have,

or expect

to have, more than $300.00 to spend for a loud-speaker system, no significant im-

provement would

be

audible if the

W-4AM were replaced with any other

commercially available

power amplifier, regardless

of price. If more elaborate reproducers were used, some improve-

ment at extremely low frequencies

might be expected through the use of

amplifiers such

as

the

Heathkit W-5M.

In this discussion, we have

attempted to convince you that your

investment in the

W-4AM

kit

is

worthy of extreme care in construction and installation. Hurried or careless

construction can

only

lead

to trouble, either initially or after some period of satisfactory

performance.

TAKE

ENOUGH TIME TO DO THE JOB RIGHT THE FIRST TIME

and

you

will be repaid many times

in personal satisfaction and long, trouble-free

service.

If you

have

built Heathkits

before,

you

will

note a change in the usual

step-by-step procedure for

assembling and wiring. The new "all-on-one-drawing" plan used in this

manual

has been

devel-

oped to

make

your work even more enjoyable.

PLEASE

READ

THE

MANUAL ALL

THE WAY THROUGH

BEFORE ANY WORK IS STARTED.

Only a very small percentage of Heathkit assemblers encounter any

difficulty whatsoever in com-

pleting kits of this kind. Large fold-in pictorial diagrams are included

in

the

manual for your

convenience and are quite helpful if attached to the wall above your work space. The

diagrams

are repeated

in small form within the manual proper.

We

suggest that you retain the manual in

your

files for future reference in the use of the amplifier and for its

maintenance.

UNPACK THE KIT

CAREFULLY

AND CHECK EACH PART

AGAINST THE PARTS LIST. DO

NOT DISCARD ANY PACKING MATERIAL UNTIL THIS HAS BEEN

DONE.

In so doing, you

will become acquainted

with

each

part and

the chance of

accidentally throwing away

some

part

will be eliminated. Full size sketches of each of the parts categories

appear on Page 16.

Use

this in checking against the

parts

list

and

in identifying any

questionable components.

Components

with wire pigtail leads canbeconveniently

sorted

by

inserting

one of the ieads into

the corrugated

edge of the shipping carton

flap. It may

be

helpful to

mark

the value of

the com-

ponent on the

flap so the part may

be readily located when needed.

If some shortage

is

found in checking

the parts, please notify

us

promptly and return the inspec-

tion slip with your letter to us. Hardware

items are counted by

weight.

An

occasional shortage

occurs

and

if this is true in your kit, please obtain the missing parts locally if at all possible.

Resistors and controls generally

have

a

tolerance rating of

±20%

unless otherwise stated in the

parts list. Therefore, a 100

Kfl

resistor

may test anywhere from 80 KH to 120 Kfl and still be

acceptable. Tolerances on electrolytic

condensers

may be

even wider and commonly run from

±100%

to -50%. The parts furnished with

your Heathkit have been specified

so

as to meet the

performance specifications given.

In order to e^qjedite delivery

to you, we are occasionally forced

to

make minor substitutions of

parts.

Such

substitutions

are very carefully checked before they are approved

and

the

parts

sup-

plied will work satisfactorily

in your kit. For example, if

your

kit is

short a 15

K(2

resistor

and an 18 K£J resistor

is

furnished

which is

notinthe

parts

list, you will understand that such

a substitution has been made.

This

fact

is

mentioned

here

only to prevent any confusion in check-

ing the contents of your kit.

CAUTION: We strongly urge that you follow the wiring and parts layout

shown in this manual.

The position of leads and parts is quite critical in the instrument and changes may

seriously

affect the characteristics of the

circuit. We do not represent that the

circuit or

layout

of

the

instrument cannot

be improved; however

the methods shown

in

this

manual are

the

result of

many

experimental

models and unless the constructor

has access to full

laboratory facilities, we rec-

ommend that they

be

followed

very closely.

Actual construction of the amplifier consists

of

three

phases, each

of which

is

covered

by a

single

drawing containing all

pertinent information necessary

for

completion:

Phase I

-

Assembly of parts to chassis.

Phase

n

-

Preliminary

wiring.

Phase

HI

-

Final wiring.

These three drawings appear on

the following pages of the manual. They 'are also reproduced in

much larger form

as

fold-in inserts included

with this manual. The large drawings should be

mounted

on the wall above

your work space where they may be referred to readily.

Notice

that each phase

consists

of a sequence of operations, which are contained in numbered

boxes surrounding

the drawing. When

a

note

is

referred to,

the

note will

be

found near the oper-

ation

box where it is first applicable. At the end

of each

operation,

a

small

space

is provided

(

).

Use this to check off each operation

as it is completed.

Then, if your

work

is

interrupted

possibility of skipping an

operation is minimized.

Start Phase I with operation

1,

in the upper left hand corner

of

the drawing. Follow the steps

in numerical

sequence.

Page

5

NOTES ON WIRING

Before proceeding with actual

wiring of yourW-4AM

kit, the following notes should

be

read

care-

fully.

1.

Notice

that

on the Phase

II

drawing,

each contact

of the terminal strips and other parts has

been identified

by a number. No numbering

is shown for tube sockets since

markings are

molded on each socket, as shown

in the sketch

under Step 1.

This system of numbering

terminals

is used to simplify wiring instructions. For

example,

when an instruction

reads,

"Connect yellow lead to

J1

(NS),

"

it will

be understood that the

yellow lead

is

to

be connected

to

terminal

number 1 on terminal

strip

J.

2.

The abbreviation

(NS)

is used

to indicate

that other connections will be made to that terminal

later and the connection

should not

be soldered yet. When the last connection has been made

to a terminal, the abbreviation

(S)

in inserted indicating that the connection should be sol-

dered.

3. The term "dress" appears several

times

in

the instructions. This means to place the

cable

or

lead

so that it reaches to

and remains near the terminal indicated. It

may be

necessary

to

form or bend the cable slightly

so that it stays in position without undue strain on the

connections.

4. "Stripand

tin" means that

the insulation on the lead should

be

removed, usuallyfor

a

distance

of

3/8"

or

so. Then twist the exposed

bare strands of wire together and

coat

with

hot

solder

so

the wire

may be easily pushed

through terminal holes without fraying out.

5.

To

avoid possibility

of error,

each color coded component is described quite completely in

the

wiring instructions.

On most resistors,

a

gold

or silver band will be found in addition

to the three colors

called out.

This

fourth

color

may be

disregarded, since

it

indicates

only

the

resistance tolerance.

6. On electrolytic condensers of

the tubular

type, one of the leads will be marked "positive"

by means of

a + sign or other method.

The instructions plainly indicate

to

which terminal

the positive lead

is to be connected.

It is very important that the condenser

be

connected

exactly

as

called

out, otherwise it will

be destroyed and

may

possibly

damage other com-

ponents

as well.

7. On paper dielectric condensers,

usually of the

molded paper type,

a

band or other

marking

sometimes appears to

designate the outside foil

of the condenser. Such markings

are not

significant in the

W-4AM

and

may be disregarded

entirely.

8.

Before doing any soldering,

read the note

on the inside rear cover of this manual.

NOTE: ALL

GUARANTEES ARE

VOIDED AND

WE WILL NOT REPAIR OR SERVICE

INSTRUMENTS

IN WHICH

ACID CORE

SOLDER OR PASTE FLUXES

HAVE BEEN

USED. WHEN

m DOUBT

ABOUT SOLDER,

IT

IS RECOMMENDED THAT A NEW

ROLL

PLAINLY

MARKED "ROSIN

CORE RADIO

SOLDER" BE PURCHASED.

9.

Unless otherwise

indicated, all wire

used is insulated. Wherever

there is a possibility

of

bare leads on

components shorting

to other

metallic objects, the leads should

be protected

by

useof

insulated sleeving.

This is indicatedin the

instructions

by the term "use sleeving."

10. Leads on most components

are longer

than they need

to be. Excess lead length

should be cut

off before the part is wired in

place. This will

not only give a neater

appearance to the

job,

but actually

improve the operation

of the equipment.

Page

7

FINAL ASSEMBLY AND TEST

This

completes

actual construction of the amplifier. Before

the shield

is

added, the

amplifier

must be

tested and

adjusted. Follow the procedure below. (If trouble is

indicated at any stage

of the

testing, refer to the section

IN CASE OF DIFFICULTY

on Page 11.

Alter corrections

have been made,

proceed with the tests.)

(

)

Check the

wiring very carefully against the drawings. Make

sure each wire is properly

soldered.

Remove any wire clippings, solder

splashes or other foreign materials.

(

)

Install tubes in the sockets as follows;

Socket

A

-

5881 Socket

C

-

6SN7GT

Socket E

-

Install no tube

in

this

Socket

B

-

5881 Socket

D

-

6SN7GT

socket as yet.

Be

sure

NO

tube is

installed

in socket

F

since this is the

power outlet for

a

preamplifier.

The

Heathkit W-4AM

Amplifier

is

specifically designed for use with the Heathkit

model

WA-P2

Preamplifier or other

high-quality preamplifiers containing controls for

program selection

tone and

volume.

If you plan to use the WA-P2

preamplifier, it should be constructed at this time

before

any

fur-

ther tests

are made. If some other preamplifier is to be used, see Page 14.

Assuming that the WA-P2

preamplifier

is

available, proceed as follows;

(

)

Connect the power

cable of the preamplifier to the

W-4AM by

plugging the

octal plug on the

preamplifier cable into socket

F

on the W-4AM chassis. Do

connect

the

shielded signal

cable to the

W-4AM

at this time.

(

)

Connect a

speaker to the

speaker terminal

strip,

using

"C"

terminal for one

lead and either

the

”4,"

"8"

or

"16"

terminal for the other lead, depending on the

nominal impedance of the

speaker being used. This information is

generally available on

the

speaker label or it maybe

obtained

from the speaker manufacturer. In case of doubt, use

the

"8"

terminal temporarily.

(

)

Plug

the line cord of the W-4AM amplifier into

an outlet delivering

105-125 volt

50-60

cycle

AC

power.

DO NOT

CONNECT TO

A DC

(DIRECT CURRENT) OUTLET,

such

as

may

be

found in some of the

older districts

of large cities. The

amplifier will not

operate on

DC

and

the protective fuse will

be

blown

if

so connected.

( )

Obtain a DC

milliammeter with a

range of not

less

than 75 milllamperes full scale,

prefer-

ably

100 ma. Connect the

positive terminal

(+)

to

the

tip

of a standard

phone plug such

as

those used for

headsets. Connect the negative terminal of the meter to the

sleeve of the

plug.

If such a meter is

not available,

it probably can be

borrowed from

a

friend, a local

amateur

operator

or

the adjustments can

be made

in ten minutes

by a

radio serviceman.

(The

Heathkit Handitester model

M-1

is ideal fortius purpose

and

also

would be

convenient

for

a multitude

of other applications, should

the

constructor be

technically inclined.)

(

)

Insert the

phone plug in either of

the

phone

jacks.

(

)

Apply

power

to

the amplifier

by

turning

TREBLE

tone control

on

the preamplifier clockwise.

The tube

filaments should light.

Now turn

the

power off

and insert the

5V4G

tube in socket

E.

Again turn the

amplifier

on

and

watch the meter

connected

to

the phone plug. It should

swing upward to indicate a current of from 40 to

75

milllamperes.

Note the reading, then

remove the

phone plug and

insert it in the other

phone

jack. Adjust

the balance control

L

between the two 5881 tube sockets so that exactly equal currents are indicated at both jacks.

NOTE;

The procedure just completed assures that

each of the

5881 output tubes is drawing the

same amount of current from the power supply.

This

balancing operation is quite critical and

affects the

low-frequency distortion characteristics of the

W-4AM.

The calibration accuracy

of

the

meter

is

not important, so long as both tubes

draw equal

currents.

Page 10

(

)

Now connect the shielded signal cable to input connector

AA.

A

loud "pop" should

be

heard

in

the speaker as this is

done

and a low hum or rumbling sound will be evident.

(.

)

It theWA-P2 Preamplifier has not been tested, this

work

should

be completed now. Follow

the instruction manual for

the WA-P2 for detailed instructions.

( )

Assuming that both power amplifier and preamplifier are behaving

properly, disconnect the

line cord

from

the

outlet and

attach the shield below the chassis. Remove the two power

transformer mounting screws nearest the center of the chassis. Mount the shield so that

it

covers sockets C

and D, using the two transformer screws. See Figure on Page 6 for

orientation of the

shield.

(

)

Install the four rubber mounting feet in the larger holes in eachcornerof the chassis flanges.

The flat side of the foot should support the weight of the chassis.

Your Heathkit W-4AM

Amplifier

is now complete

and

ready for

permanent installation.

Since

there are no

operating controls on

the amplifier itself, no

operation instructions

are required

All control functions

are

supplied

by the

preamplifier.

IN CASE

OF DIFFICULTY

If

the test procedure above indicates that things

are not normal, follow the

plan given below:

1. Recheck the wiring. Trace each lead

in colored pencil on the

drawings as it is checked.

Most cases of

difficulty result from wrong connections. Often

having

a

friend check the

wiring will reveal a mistake

consistently overlooked.

2. Check

the tubes. Most radio service shops

will do this at no charge or for a nominal fee

3. If

possible, check tube socket voltages against the chart below. Agreement within

20%

can

be expected. If a

discrepancy

is

apparent, check the wiring and

components associated with

the circuit tmder suspicion.

VOLTAGE

CHART

SOCKET

TUBE

TYPE

Pin

1 Pin 2

Pin

3

Pin

4

Pin 5 Pin 6 Pin 7

Pin 8

Aor

B

5881

NC

H

370 V

375 V

NS

NS

H 38 V

C

6SN7GT

NS

135

V

4.0

V

NS

135 V 4.0 V H H

D

6SN7GT

NS 54 V 1.2 V 54 V 200 60 V H

H

E

5V4G

NC

440

V* NC 380 vac

NC 380 vac NC

440

V*

F

Preamplifier

Power

H H

0

250 V

275

V

See

Table,

Page

13

All voltages positive

DC

to chassis,

measured with

Heathkit

V-7

VTVM (11

megohm input).

Voltages measured with Heathkit

WA-P2

Preamplifier connecled. Line voltage, 117 volt AC.

NC

-

no connection.

NS

-

reading not significant.

H

-

vbltage between points marked, 6.3 volts

AC.

*

Voltage between points marked, 5.0

volts

AC.

4.

If

difficulty still

persists, touch socket terminal

A5

with

one lead of a

.01 fifd

paper conden-

ser, holding the condenser

by its

other lead.

(CAUTION:

Do not touch chassis

or any other

metallic body with your other hand

while

making

this

test. Dangerously high voltages are

present throughout the amplifier circuit and

due

care should be exercised.

)

A

decided

in-

crease

in hum at the speaker should

be

noted.

If

terminal

A5

is "hot" as

indicated

by

hum

increase, try terminals

BS,

C2,

CS,

D5, D2

and

Dl. At some

point in this sequence, no hum

UNUSUAL

TROUBLES AND CORRECTIVE PROCEDURES

Certain difficulties

often

appear to

originate

in the power

amplifier but actually have their source

in associated

equipment.

Some

of these

are

outlined

below.

1.

High hum level at the loudspeaker may be caused

by

several external effects. Assuming

that the W-4AM is used with

aWA-P2

preamplifier,

a

very decided reduction in hum will be

noticed upon proper setting of the

"HUM"

control on the preamplifier. This will take place

at nearly the center of rotation. To check hum level, adjust the volume control for slightly

higher

than normal

room volume. Then lilt the pickup arm from the record or turn off

power to the tuner being used for

a program source. The hum level at the loudspeaker

should just barely be audible at

a

distance

of three feet or so from the speaker. A louder

hum indicates abnormal conditions which can generally

be corrected. Try

the following:

(a) Reverse the

line

cord in its outlet for minimum

hum.

(b)

Try

disconnecting

the shield of the signal cable

at the

power-amplifier

end

where

it con-

nects

to

the shell of the phono

plug. This will prevent

a "ground loop" through

the

shield of

the cable which might actually induce

hum rather than eliminate

it.

(c) Try

eliminating possible

"ground loops" between various program

sources

(phono pick-

ups, tuners, recorders, etc.) and the

preamplifier

by

opening the shield grounds at one end

or the other.

(d)

Try disconnecting

each

program

source from the preamplifier and determine If the hum

level is affected in any

way.

Even

idle

tuners

or phono pickups will occasionally develop

into hum sources because of leakage

in power circuits.

(e) As a

last resort, try connecting

the frame orchassisof eachcomponent to a good ground

such as

a

cold water pipe or driven

ground.

2. "Motor boating" is a term used to describe

a

low-frequency

(2

to 5 cps)

oscillation of an

amplifier system. It is generally caused

by

inadequate amplifier

loading at

low frequencies.

For example, a speaker with

a

nominal

impedance of 160 may actually

look

like

150 to 200

Q at frequencies near speaker

system

resonance.

Sufficient low frequency stability is

in-

cluded in the

W-4AM

to prevent this

difficulty in the vast majority of cases.

However, all-

inclusive safety margins

are quite expensive.

In

general, the better speaker systems are

less likely to

cause

trouble in

this way.

Under no conditions should shielded

speaker leads be used and every attempt

should

be made

to keep the capacity across speaker lines

to a

minimum. Other less frequent

causes

of

motor boating are:

(a) Unbalanced output tubes. Recheck balance settings.
(b) Defective filter condenser sections,

either in the power amplifier or preamplifier.

(c) Feedback factor too high. Feedback

is

controlled

by

the 4.7

KQ

1

watt resistor from

AB2

toD3. In rare

cases,

it

may be necessary to increase the value of this resistor to eliminate

motorboating.

A

change

to 6.8

KR

will generally

correct a

persistent

case,

with very slight

degradation to performance in other

respects.

(d)

Low frequency oscillation

may sometimes be triggered or touched off because of oscilla-

tion of the amplifier at

a

supersonic

frequency around 100 kc. This type of difficulty will

cause the

amplifier

to sound strained

or

muddy. It may be

readily identified

by

connecting

an oscilloscope across the speaker terminals.

If oscillation is present, it

will

be

evidenced

by a steady high frequency output voltage

with a highly

distorted

wave

form. This output

voltage will

exist even in the absence of input signals.

The

condition

may be

caused

by

an

improper or defective condenser across

the

feedback resistor or

by

improper components

in the phase correction network,

the 4.7 KR resistor and

420

ppf condensers connected to

D4

and

G

.

.

Page 12

3.

Output tubes will not

balance.

First, try

interchanging

the tubes

in sockets

A

and

B.

If

the

unbalanced effect is also interchanged, one of the tubes is

probably defective. If not, care-

fully

check the

wiring associated with the cathode circuits of the output

tubes. Bie

sure

neither of the jacks is

shorting to

the chassis;

they should

be

completely free of metallic

contact to chassis

except through the 360

SI

bias resistor and the balancing

network.

Check

voltages

carefully against the voltage chart if

unbalance still persists.

Do

not attempt to

balance

tubes while program material is being

reproduced.

INSTALLATION

When

the amplifier is

completely tested, it should be

permanently installed in the system. Since

no operating controls

are associated with the W-4AM, it

may be installed

wherever convenient

with the following

precautions:

(a) Allow

sufficient ventilation to prevent

overheating. Bear in mind

that while in operation,

the unit

will develop about as much heat as a

150 watt lamp bulb.

(b)

Provide access room

for connecting cables,

occasional balancing of

the output tubes and

tube

replacement.

(c)

Protect the

amplifier from dampness

or physical damap. Since

the tubes run very

hot,

the

unit should be

installed where it cannot be tampered

with

by

small children.

An

AC

outlet is

provided on control

apron of the amplifier. It may be

used to

supply power to a

tuner,

phonograph record

changer

or other

accessory. If

used for a record

changer,

be

sure the

unit is

allowed to pass

completely thru its change cycle so it shuts

itself off.

Otherwise, idlers in

the changer

may be left in contact with other

parts causing flats

to develop and ruining

the idlers.

A

complete

discussion of how to install the

high fidelity system is

too lengthy

to carry in this

manual. We

suggest a review of current issues of

"High Fidelity"

and "Music at Home.

"

These

magazines

carry specific sections on

installation. This

type of

information also appears fre-

quently in other

periodicals on home

building and decorating.

USING

THE W-4AM

AMPLIFIER

WITH OTHER

PREAMPLIFIERS

As

previously

stated, the W-4AM is

designed specifically

for use with

theHeathkit model WA-P2

Preamplifier.

It may,

however, be used with

other preamplifiers or AM-FM

tuners which in-

corporate

the

necessary control functions.

Sufficient

power is

available from the W-4AM

to operate

both filament and

plate circuits

of the

usual

preamplifier

where Independent power

supplies are not

included

in

the

preamplifier

itself.

The

following circuits

are available at

socket

F;

275 volts

DC

at 10 ma

117 volts

AC,

switched

and fused

117 volts

AC,

not switched

and fused

Line switch, to

control

amplifier

Socket

contacts FI

and

F2.

Socket

contact

F3.

Socket

contact

F4.

Socket contact F5.

Socket

contacts F7

and

F8.

Socket contacts F6

and F8.

Socket

contacts F6

and

F7.

It is

suggested that an

adapter cable be

made up to

supply power

and/or switching

circuits to

preamplifiers other

than theWA-P2. This

cable should

terminate

in

a

standard

octal plug, with

cap,

similar to

Amphenol's type 86-PM8,

and may be

wired in

accordance

with the above infor-

mation. The

cable may

then

be

connected to the W-4AM

using socket F.

DO

NOT, UNDER ANY

CIRCUMSTANCE,

EXCEED

THE

POWER RATINGS

GIVEN ABOVE

FOR

ADDITIONAL FILAMENT

AND PLATE

SUPPLY.

To do so may

seriously

damage

power supply

components in your W-4AM

amplifier. If the

preamplifier

used has no

provision for hum

bal-

ancing

through an

adjustable resistor across

the

filament line, it will

be necessary

to ground

the

center tap of the

filament winding of the W-4AM

power

transformer. This

can be

done by

connecting

to

chassis

the green-yellow lead

passed

through grommet YP.

This may be

done by

soldering the

lead to

terminal strip PI

Page 13

REPLACEMENTS

Material supplied with Heathkits has been carefully selected

to

meet design requirements and

ordinarily will fulfill its

function without

difficulty. Occasionally improper instrument opera-

tion can be traced to a faulty tube or component. Should inspection reveal the necessity for

re-

placement, write to the Heath Company and

supply all of the following

information;

A.

Thoroughly

identify the part

in

question

by

using the part number and description found in

the

manual

parts

list.

B.

Mention

the order

number and date of

purchase.

C.

Identify the type and model

number

of kit in which it

is used.

D.

Describe the nature of defect or reason for requesting

replacement.

The Heath Company will promptly supply

the necessary replacement. Please do not return the

original component until specifically requested

to do so. Do not dismantle the

component

in

question

as

this will void the guarantee.

K

tubes are to be returned,

pack

them carefully

to

prevent

breakage

in shipment as broken tubes

are not eligible for repUcement. This replace-

ment policy does not cover the free replacement

of parts that may have been broken or damaged

through carelessness on the part of

the kit builder.

SERVICE

In event continued operational difficulties

of the completed instrument are experienced, the fa-

cilities of the Heath Company Service Department are at your disposal.

Your instrument may

be

returned for

inspection and repair for

a

service

charge of

$6.00,

plus

the price of any additional

material that may be required.

THIS SERVICE POLICY

APPLIES ONLY TO COMPLETED

ttlSTRUMENTS CONSTRUCTED IN ACCORDANCE

WITH THE INSTRUCTIONS AS STATED

IN

THE MANUAL. Instruments that are not entirely completed or instruments that are modified

in design will not

be

accepted for repair. Instruments

showing evidence of acid core solder or

paste

fluxes

will

be

returned

not repaired.

The Heath Company

is

willing to offer its full cooperation

to assist

you

in obtaining the specified

performance level in your

instrument.

Factory repair service is available to you or you may

contact the Technical

Consultation Department

by mail. For

information regarding possible

modification

of

existing kits, it is suggested that

you

refer

to

any

one

or more of the many pub-

lications

that

are

available

on all phases of

electronics. They

can

be

obtained

at or

through your

local

library, as well as at any electronic outlet store. Although

the

Heath Company sincerely

welcomes aU

comments and suggestions,

it would be

Impossible

to

design,

test,

evaluate and

assume responsibility for proposed circuit changes for specific purposes. Therefore, such

modifications must be made at the discretion of the kit builder according to information which

will be

much more readily available from

some local

source.

SHIPPING INSTRUCTIONS

Before returning a unit for service,

be sure that all

parts are securely mounted.

[

ATTACH A TAG TO

THE

INSTRUMENT

GIVING I

NAME, ADDRESS AND TROUBLE EXPERIENCED.

[

Pack in

a

rugged container, preferably

wood, usii^ at least three

inches

of

shredded newspaper

or

excelsior on all

sides. DO NOT SHIP IN THE

ORIGINAL KIT CARTON

AS

THIS

CARTON IS

NOT CONSIDERED ADEQUATE FOR

SAFE SHIPMENT OF THE COMPLETED INSTRUMENT.

Ship by prepaid express if possible. Return

shipment will

be

made

by

express collect.

Note that

a carrier cannot be held liable for damage in

transit if packing, in

HIS OPINION, is

insufficient.

All

prices are subject to change without notice. The Heath

Company

reserves

the right to

dis-

continue instruments and to change specifications at

any time without incurring any

obligation

to incorporate new

features

in

instruments

previously sold.

Page

14

WARRANTY

i,

li present,

may

PART

PARTS

DESCRIPTION

No.

Per Kit

Resistors

1-3 2

100 n

1/2

watt

1-48

1

390 n 1/2

watt

1-5A

1

22 KS2

1 watt

1-6 1

470 Q 1/2

watt

1-9

2

1

K£1

1/2

watt

1-16

1

4.7 KSl

1/2

watt

1-21

2

15

KD 1/2

watt

1-24 1 33

Kfl

1/2

watt

1-25 1

47 KO 1/2

watt

1-26 2

100 KO

1/2

watt

1-33 3

470 KSl 1/2

watt

1-5A

2 22

KO 1 watt (matched)

1-15A

1

47

n

1

watt

1-22A

1

1.5 KO

1

watt

1-48A

1

4.7 KD 1

watt

1-28A

2

100

KO

1

watt

1-llB

1

22 Kfi 2

watt

I- lOB 2

47 KO

2 watt (matched)

3-7G

1

360 n 7

watt wirewound

II- 1

1

100 n control

Condensers

20-

34 1 350

niif

mica

21-

23

1 420

fifjif

ceramic

23-61 1

.05

(ifd 400 volt

paper

23-28 1

.1 fifd

200 volt

paper

23-63 4 .

25

jifd

400 volt paper

25-19 1 20 lifd

150 volt

electrolytic

25-16 2

20

pfd 350

volt

electrolytic

25-21 1

20-20-20-20 (rid

450 volt elec.

411-15 2 6SN7GT
411-35

1

5V4G

411-45 2 5881

Sockets

-

Jacks

-

Plugs

-

Fuse

434-42

1

Phono

input socket

434-20

1 AC

power socket

434-58

6

Octal

tpbe socket

436-4

2

Phone

jack

438-4 1

Phono plug

421-2

1

Fuse

A423-2

1

Fuse

holder short

PART

PARTS

DESCRIPTION

No.

Per

Kit

Terminal

Strips-Wafer

431-1

4

1-lug

terminal strip

431-2 1

2-lug

terminal

strip

431-4 1

3-lug

terminal strip

431-5

1

4-lug

terminal strip

431-13 1

4-screw

terminal strip

481-3 1

Condenser

mounting

wafer

Sheet

Metal

Parts

200-M86F101

1

Chassis

206-M22

1

Shield

Wire

89-1

1

Line

cord

340-3 1

length Solid

wire

344-1

1

length Hookup

wire

346-1 1

length Sleeving

Transformers-Chokes

51-17

1

Output

transformer

54-29

1

Power

transformer

46-12

1

Filter choke

Hardware

73-1 2 3/8"

grommet

73-2 4 3/4"

grommet

250-9 24

6-32

x

3/8" screw

250-17 12

8-32

x

1/4"

screw

252-3 24

6-32 hex nut

252-4

12

8-32

hex nut

252-

7 3

3/8-32

hex nut

253-

10 3

Flat nickel

washer

253-15 2

Flat fiber

washer

253-

16 2

Shoulder

fiber washer

254-

1

24

#6

lockwasher,

internal

254-6 7 #6

lockwasher,

external

254-2 12

#8 lockwasher

254-4

1

3/8" lockwasher

259-1 2 #6

solder lug

261-1 4

Rubber feet

595-107 1

Instruction

manual

Page 16