Hafler DH-200 User Manual

THE

Hafler DH-200 Power Amplifier

POWER

INSTRUCTIONS

AMPLIFIER

for OPERATION

and KIT ASSEMBLY

CAUTION:
IF THE SPEAKER FUSES BLOW,
SOME DISTORTED SOUND CAN BE
HEARD. THEREFORE
MALFUNCTIONS, ALWAYS CHECK
FOR BLOWN FUSES FIRST.

THE DAVID HAFLER COMPANY

5910 Crescent Boulevard, Pennsauken, New Jersey 08109

IF AMPLIFIER

serial

number in all

communications

INTRODUCTION

DH-110

The Hafler DH-220 is a two channel audio power amplifier
designed to the very highest performance standards. It is
available either as a kit, or fully assembled. Its 115 watt per
channel power rating is sufficient for driving all loudspeakers in
home applications, and its design assures extremely low distor­tion of all types. A combination of high performance, depend­ability, reliability, and moderate price is in the Hafler tradition of
using the very latest technology to provide outstanding value.

The DH-220 circuit is a refinement of the DH-200 design, a

Hafler landmark which has achieved worldwide recognition,

and has elicited glowing reviews since its 1979 introduction. As
in the DH-110 preamplifier, particular attention has been paid to
component quality, using polypropylene or film capacitors
wherever feasible, for example, for superior sound.

Combining the latest power MOSFET technology with uni­quely simple and effective circuit topology reduces distortion of
all types, and at all power levels, over the full audio frequency
spectrum, to the vanishing point. In addition to its pace-setting
performance achievements, the conservative mode of opera­tion accomplishes a new high in long term reliability and
tional resistance to abusive operating conditions. This is one of
the direct benefits of MOSFET utilization in overcoming a
serious limitation of conventional transistors
to self-destruct under other than normal operating conditions.
So rugged is the DH-220 that it can deliver more than ten
amperes into a short circuit!

The speed

delivers unmatched transient linearity, revealing the most

delicate shadings, textures and nuances of the music, surpassing
the capabilities of the most revealing loudspeakers and cart­ridges by a wide margin. Coupled with its unconditional stabili­ty, and ability to deliver adequate power into any loudspeaker
load, the result is absolute freedom from listening fatigue. The
longer you listen to this phenomenal amplifier, the more certain
you will be that you could not have made a better choice.

-

measured as the slew rate - of this design

-

their tendency

excep-

The oversized power transformer and bridge rectifier; the
massive heat sinks; the conservative operating levels of the
MOSFET output devices
to achieve exceptional reliability simultaneously with state of
the art sonics and specifications. And this circuit is convertible to
a high power monophonic amplifier with comparable stability
and specifications.

The fully complementary, symmetrical push-pull circuit,
which is direct coupled throughout (except at the input), incor­porates all silicon devices in a format which is directly related to
the highly acclaimed DH-110 preamplifier. Its unique
protecting output stage prevents the thermal runaway which is
a common threat to solid state amplifiers. The ruggedness and
conservative operation of the output stage allows the DH-220 to
avoid the need for special protective circuits which could com­promise audio performance. Basic protective systems provide
maximum security against malfunction damage to the amplifier
or the speaker: the AC line fuse, B + fuses, thermal breakers,
and loudspeaker fuses. Nothing hinders the essential purity of
the audio signal.

Those who use these instructions to assemble the DH-220 kit
will find that the left and right audio modules (printed circuit and
heat sink assemblies) are preassembled and pretested. This
greatly simplifies the kit assembly so that it can be done in only a
few hours without special skills or know-how. Because of
modular arrangement, it is possible to operate on one channel if
the other requires service, and avoids the need to return the en­tire amplifier in cases where only one channel is at fault.

Accessories for special applications include provision for
monophonic use; a panel for standard 19” rack mounting; and
an alternative power transformer for international AC line
voltages.

Through advanced engineering geared to the audio perfec­tionist, and an efficient no-frills approach, Hafler is making high
technology high fidelity affordable.

-

all are evidence of the design efforts

self-

the

Operation........................

Assembly Instructions

Wiring the Kit
If Problems Arise.
Service and Warranty

Copyright 1984, All rights reserved.

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CONTENTS

Page 3

4

6
10
11

AC Line Connections for Overseas Use.
Kit Parts List
Schematic Diagram
Component Value Listing.
Pictorial Diagram.

.........................

...................

..............

..................

...

Insert

12
13

14

15

INSTALLATION

DH-101

The

DH-220

applications, since its power may be controlled by the AC
switching of most audio preamplifiers, like the Hafler DH-110. If
your control unit does not provide switching capacity sufficient
for the amplifier’s 7 amp needs (plus other equipment it is also
switching), you should use the amplifier’s own power switch. In
that case, turn on the preamplifier first; then turn the amplifier
on a few seconds
any unnecessary turn-on transients from some preamplifiers.
Likewise, switch the power amplifier off first.

is most likely to be installed out of sight in most

after

the preamp has been turned on, to avoid

than others, and require separation from the amplifier. Check at
a comparatively high volume setting, and while swinging the
tone arm throughout its arc. Often a few inches additional spac­ing will eliminate the problem.

Be sure to provide sufficient

Unobstructed

above

the amplifier is important for long, trouble-free life. Never

air circulation

ventilation

for the amplifier.

around the finned heat sinks and

put anything on top of the cover perforations. It is normal for the
top and the heat sinks to become warm in use.

If the amplifier is to be installed close to a record player, you
should first check its position for freedom from hum pickup by
the cartridge from the field radiated by the power transformer
of the DH-220. Although the design of the transformer
minimizes such radiation, certain cartridges are more sensitive

OPERATION

The red pilot lamp which is integral with the power switch
glows whenever the amplifier is turned on. A blown AC line fuse
is the most likely cause if it is not illuminated when the amplifier
is switched on.

The pilot lamp also provides a high temperature indication. In
the unlikely event that the amplifier ceases to function, and the

amp blinks on and off steadily, it indicates that one of the ther­mal breakers has shut down the amplifier because of excessive
temperature rise in a heat sink. When the heat has dissipated in
a few minutes, the amplifier should return to normal operation.
If the lamp again blinks, check for insufficient ventilation, or an
excessive input signal, or an input which may have dangerous
signal content (such as oscillation). Failing evidence of this, the
amplifier may have malfunctioned. Because of the very large
heat sinks, it is highly unlikely that any normal signal will cause
the amplifier to overheat.

Loudspeaker Fuse Selection

The DH-220 power amplifier is supplied with 2 amp fuses in
the speaker lines. Experience has shown that since an overload
must exist for a few seconds for a fuse to blow, a 2 amp fuse will
protect most speaker systems, and only blow when overload oc­curs. Smaller fuses tend to blow too easily, and larger fuses do
not adequately protect most speaker systems.

It is expected that the amplifier will always be resting on its
feet, which should be on a hard enough surface that air flow
underneath is not obstructed. If it is mounted in a rack, or
through a panel, the feet may be removed so long as adequate
ventilation is provided through the bottom openings.

Loudspeaker Power Ratings

There are no U.S. standards for rating the power handling of
loudspeakers. As a result, the manufacturers’ usual “music
power”ratings, or suggested amplifier limits, are of only
minimal help in determining safe operating levels with
amplifiers which can deliver substantial amounts of power. You
must take into consideration the type of music, and the levels
you like, to provide long term trouble-free operation of your
speaker choice, when you have a sizeable amplifier like the
DH-220.

Connections

AC

The AC power cord should be plugged into 120 volts, 60 Hz,
on the switched outlet of a preamplifier which can provide at
least 7 amps, or 840 watts. Then the amplifier power switch may
be left on, and it will be controlled by the rest of the system. Or. it
may be plugged into a 120 volt wall outlet, and switched on and
off independently.

If your line (mains) voltage is different, be sure you have the
alternate power transformer which can accommodate several
line voltages, and be sure it is wired for your mains voltage as
described later in this manual

before you pIug in the amplifier.

A pair of 5 amp fuses are also supplied as alternatives for the
speaker fuse holders. These should be substituted if the power
output of the amplifier is to be tested, and these or intermediate
values may be used if the amplifier is to be operated at very high
power levels into 4 ohm loads.

If the manufacturer of your speakers recommends a specific

value of fuse for their protection, we suggest that you obtain

AC

fuses of that value and install them in the back panel.

Input

Conventional shielded cables, such as those supplied with
your preamplifier, provide the input signal to the sockets on the
back panel of the DH-220. Be sure that the outer shield connec­tion is secure, to avoid hum. The length of these cables (so as to
permit remote location of the amplifier, if desired) is limited only
by the output impedance of the preamplifier. If it is 600 ohms or
less, as with the DH-101 and DH-110 Hafler preamps, for in­stance, cable lengths up to 50 feet are premissible without loss of

performance. Special low capacitance cables enable even
greater distance between preamp and amplifier. It is desirable
to keep the left and right input cables close together throughout
their length to minimize the likelihood of hum pickup. Also, you
should avoid running them parallel to AC cords
be crossed at right angles.

Output

The loudspeakers (or headphones) connect to the red and
black terminals on the back panel. These binding posts provide
several convenient alternative connecting methods. The screw
cap may clamp the bared wire end, or a “spade lug” attached to
it, but a better connection will be made by locating the hole drill­ed through the shaft of the terminal when the cap is unscrewed.
Insert the twisted end of the bared wire so that the cap will
clamp it in place. Always be sure that no strands of wire are
unsecured, and that the bared end is not too long to risk contac­ting other elements. A soldered end or fitting is the safest solu­tion.

-

these should

plugs are used, be suretheyare color coded, or that you follow
the indexing mark ononeside of the double connectors.

Select speaker wire of sufficient size to preserve the high
damping factor (and excellent speaker control) of your
amplifier. Standard 18 gauge lamp cord (“zipcord”) is satisfac­tory for distances up to 30 feet for an
distance increases, larger wire sizes are recommended. The
next larger wire size is
tionists. If you have 4 ohm speakers, the maximum cable length
for best results is halved.

The black output terminals are electrically connected to the
chassis internally. Be certain that when the amplifier is operated
in its normal stereo mode that the red output terminals are never
connected together. In the special case when the amplifier has
been internally modified for monophonic bridged operation,
the output is taken from the two red terminals
black terminals are left unconnected.

#16,

and it is often preferred by perfec-

8

ohm speaker. As the

only.

Then, the

These terminals also accept standard plug-in “banana pin con­nectors,” including the double ones with standard
available from electronic supply houses. These are the most
convenient, especially if you may wish to interchange speakers
occasionally.

It is important to maintain correct phasing of the speakers
when making their connections. Some speaker terminals are
coded red and black, or + and
“sense” of one speaker’s connections match the others. If one is
reversed, you will find that the sonic image has a “hole in the
middle,” and that it is deficient in bass. Speaker wire always
identifies one conductor to make this easy. There may be a
molded ridge in one lead, or the color of the insulation on one
wire is different, or the wire itself may be color coded. If pin

-,

etc. It is important that the

3/4”

spacing,

KIT ASSEMBLY INSTRUCTIONS

There are three basic rules for success in electronic kit

building:

1. Read the instructions carefully, and follow them in order.

2. Make secure solder connections which are bright and

smooth.

3. Check your work carefully after each step.

The DH-220 amplifier is a versatile component with
sophisticated circuitry which has been made remarkably easy
to build by individuals with many years of experience in the
design and engineering of the finest performing audio kits, and
in the preparation of their manuals.

Kit building should be fun, and we are certain you will find this
to be so. Assembly will be faster, easier, and more enjoyable if
you have someone help you by reading the steps aloud, selec­ting the required parts, and preparing the necessary wire
lengths in advance as you proceed. Fatigue increases the risk of
error, so take a break rather than push to early completion.
There are relatively few separate components in this design, to
make it easy to pack everything away, if need be.

Headphones are normally operated from the loudspeaker
outputs, but are usually connected through a junction box
which provides switching from phones to speakers. Such a box
usually provides some added resistance to reduce the sensitivity
of the phones, and thus minimize the likelihood of hearing com­ponent noise, because of the low setting required at the volume
control. Some headphone boxes utilize a “common ground”
system which makes it particularly important that you carefully
observe the proper connections. While the black ground ter­minals can be connected together, the red ones must not be.

Some headphones, such as electrostatic types, are less sen­sitive and may need little or no resistance in series for normal
operation. These could be easily interchanged with the
speakers through the use of double banana plugs.

Your work area should have good lighting, the proper tools,
and a place where the large pictorial diagram can be positioned
within easy reach for checking. The tools should include:

A 40 to 100 watt soldering iron with a

1,

reaches at least
60/40 (60% tin) ROSIN CORE solder,

2.

smaller. (Smaller diameters are easier to work with.)
A damp sponge or cloth to wipe the hot top of the iron.

3.

A wire stripping tool for removing insulation. This can be a

4.

single-edge razor blade, but inexpensive stripping tools are
safer, faster and easier.

A medium-blade screwdriver (about

5.

6.

Needle-nose pliers (a long, narrow tip).

7.

Diagonal or side-cutting small pliers.
Large “gas” or “slip-joint” pliers.

8.

9.

A

1/4" “Spin-tite”

necessary.

600°F.

nut driver may be helpful, but is not

1/4"

or smaller tip which

1/16"

diameter or

1/4"

wide).

A soldering “gun” is

not

recommended. The unfamiliar user is
more likely to damage the etched circuit boards with its higher
heat potential and unbalanced weight. Also, because he may
not wait long enough for it to reach operating temperature each

time it is switched on, poor solder connections are more likely.

Pencil irons are much lighter and easier to use, and there is no
waiting time when solder connections follow in sequence, as in
kit building. Make sure you have a holder for it, though, and

always unplug it when you take a break.

Proper Soldering

There are four steps to making a good solder connection:

Make a good mechanical connection to hold the wire in posi­tion while heat and solder is applied.

Heat

thejunction

of the wire and lug, or hole, with the bright,

shiny top of the iron.
After heating for a couple seconds, apply solder to the junc-

tion. It should melt immediately and flow smoothly around
both surfaces.

Allow the connection to cool undisturbed.

Remember that the connection is made by the solder, not by
mechanically attaching the wire to the terminal. Usually the
wire is looped through the lug and crimped in place, but some
prefer to just place it through the hole and rely on the stiffness of
the wire to hold it while soldering. Connections to numbered
holes on the circuit board are handled this way.

Good solder connections are

essential

for trouble-free

noise-

free operation. A good solder joint does not require much solder

around the conductors. Never “butter” partially melted solder
on the joint, as it is useless. A good connection looks smooth and
bright because the solder flows into every crevice when the
parts are hot enough. The iron must have a bright, shiny tip to
transfer heat easily to the junction. That’s why the damp sponge
should be used frequently to wipe the tip, and occasionally you
must add a small amount of solder to the tip, too. If a connection
is difficult to heat, “wet” the tip with a small blob of solder to pro­vide a bigger contact surface to the joint. Once the solder flows
around the conductors, any movement must be avoided for a

few seconds to allow a good bond. When cool, check the con­nection by wiggling the wire. If in doubt, or if the connection is

not shiny, re-heat the joint. Excess solder may be removed from
a connection by heating it and allowing the solder to flow onto
the iron, which is then wiped on the sponge.

ALL SOLDER USED MUST BE ROSIN CORE.

Never use acid core solder or any separate flux in electronic
work. Silver solder is also not suitable. If in doubt about unmark­ed solder, always obtain a fresh supply of rosin core solder. We
recommend 60/40 for easiest use. Do not confuse it with 40/60,
which is harder to melt.

The general procedure is to use a hot iron for a short time to

heat a connection, then add solder with the iron still in contact.

Remove the solder once it flows, and then remove the iron. A
cooler iron applied for a longer time is more likely to damage
components, or lift the copper circuit pattern from the boards. A
break in the etched circuit can be mended by simply soldering a
small piece of wire across it. Do not allow much build-up of
solder on the tip of the iron, or it may fall into adjacent circuitry.

When soldering to a numbered hole on the board, insert the
wire from the components side, and apply the iron, leaving
some bare wire exposed so that you can see that the hole is then
filled with solder for a secure bond. A round wooden toothpick
is suggested so that you can heat and clear the hole of solder if it
hinders your inserting the wire. Some builders prefer to clear
every hole first with a touch of the iron and toothpick. If the wire
has first been “tinned,” no additional solder may be necessary if
solder fills the hole, but it is good practice to push the wire
through, and then back it up a bit, to be sure solder fills the hole
from both sides. Make certain a bright, shiny flow is evident
from the wire, across the hole, onto the circuit pattern on the
board.

“Tinning” refers to the process of applying a light coating of
solder to the bared wire end. This keeps all the strands secured,
and also makes a good connection easier. Simply touch the wire
with the iron for a couple of seconds, and apply solder. Allow the
excess to flow away onto the iron. When properly done, the
wire is uniformly bright, and no larger than before. The hookup
wire supplied with this kit does not normally need tinning, for it
is pre-tinned.

5

Wiring the Kit

If any components are unfamiliar to you, checking the pic­torial diagram should quickly identify them. Or, the quantities,
and the process of elimination as you check the parts list, will
help. The pictorial diagram is necessarily distorted to some ex­tent for clarity, so that you can trace every wire in a single
overall view for verification as you work. You may wish to
check off on the diagram as you solder each location.

To “prepare” a wire means to cut the designated length from
the coil of that color, and strip about
end. The wire supplied in the kit is
wire-strippers accordingly. The transformer leads are
#18

and the line cord is
wire when you strip it (that can happen more easily if you do not
use wire strippers) for that weakens it. The wire supplied in this
kit is “bonded stranded,” which provides exceptional flexibility
with resistance to breakage for easier use, and it is pre-tinned.

#16.

Be careful that you do not nick the

1/4"

of insulation from each

#18,

so you can set adjustable

#16

or

find it easier to first start them with a regular screwdriver, to set
the thread, and then use the more convenient nut driver, if one
is available.

Mechanical Assembly

1 r When you unpack your kit, you will find that the

transformer, large capacitors, and the output assemblies
have been temporarily fastened to the chassis for safe
shipment. Disengage these, and include this hardware
with the rest when you check off the components
against the parts list in the back of the manual. We
recommend this check-off to be sure you have
everything, and to enable you to identify any unfamiliar
items by comparing them with the pictorial diagram. An
egg carton is ideal for keeping hardware items
separated.

Whenever a connection is to be soldered, the instructions will
so state, or indicate by the symbol (S). If more than one wire is to
be soldered to

(S3),

etc. If soldering is not called for, other connections have
yet to be made to that terminal. They would be more difficult if
the connection was already soldered. Every connection in the
kit will be soldered when it is complete. After soldering a con­nection, it is best to clip off any excess lead length to minimize
the possibility of a short circuit (as on switch lugs, where ter­minals are very close together), and for a neat appearance.

Be sure that uninsulated wires cannot touch adjacent ter-

minals or the chassis metalwork.

The symbol
point. When a lug number is specified without (#) it is simply a
locating reference.

When the instructions call for twisting two or three wires
together, the length of wire indicated anticipates a fairly tight,
uniform twist by hand, of three full turns every two inches. If
you find the wires too short, loosening the twist will gain some
needed length.

Handle the circuit boards carefully. They represent a major

part of the kit cost. Stand-up components, such as transistors,

should be checked when you install the module, to be sure all

leads are separated.

the

same terminal,

(#)

indicates a connection is to be made to that

they

will be indicated by (S-2),

A “set” of hardware includes one screw and one KEP nut (with
its attached lockwasher). Always install the lockwasher side of
the nut first. If the size of the hardware is not specified, use the
size. The smallest size is
the screw from the outside of the chassis.

It will simplify matters if you first separate the
#6

nuts, which have the same outside dimensions. A #4 screw

will pass through a

2

L

Select the four rubber feet, four sets of #6 hardware, and

the chassis. Insert each screw through a foot so that the
head is recessed, and install the feet on the outside at
each corner hole.

3

1

Select th

sequence shown below, in the two center holes LR and
RR marked
tighten the first nut, unscrew the cap to expose the hole
drilled through the threaded shaft. Connection of loud­speaker wires will be easier if these holes are positioned
vertically. A nail through the hole will keep it positioned
while the hardware is tightened. Each connecting lug
should point downward before the last nut is secured. Be
sure both nuts on each terminal are
ficult to reach when the amplifier is completed.

e wo red output terminals. Install them in the

t

#4

and

#lO

the largest. Always insert

#4

nuts from the

#6

nut, aiding identification.

'

+’

at the rear of the chassis. Before you fully

tight,

as they are dif-

#6

All of the active circuitry is contained on the PC-19 board,

which has been carefully tested to assure that it meets every

specification. Only the interconnection of power supply

elements is left to the builder. Take the time to be accurate and
neat, and you can be sure that your completed amplifier will
meet the performance of a factory assembled unit, and can con­tinue to perform properly for years to come. Check your work,
and make sure the entire step has been completed before plac­ing a check mark in the space provided, and continuing on to
the next step.

KEP nuts have been supplied as a convenience. These have
lockwashers attached, and the lockwasher always goes onto the
screw first. If the sheet metal screws have hex heads, you may

4 Select the two black output terminals and install them or

either side of the red ones, at LB and RR. Be sure the
shaft holes are vertical, the lugs point downward. and
each nut is tight.

6

5 n Select the two round fuse holders, and two each

1/2”

rub­ber washers, lockwashers and nuts. First install the rub­ber washer on the holder, so it will be outside the chassis,
and then fasten the fuse holders at LF and RF, with the
tip lugs pointing towards each other, toward the center
of the chassis.

6

U Select the two input sockets and 4 sets of #4 hardware.

Install the sockets

inside

the chassis at LS and RS so that
the short lug of each socket is near the hole between the
two sockets.

7

0

Select the single ground lug (with lockwasher teeth) and

one set of #4 hardware. Install it between the input
sockets, pointing toward the bottom. Bend it out for ac­cess, and twist it
Be sure this lug is

90°

for easier insertion of a wire later.

tight,

as the locking teeth must cut

through the chassis paint for a good ground connection.

8

ri

Select the four-lug diode block DB, the long #6 screw,

and a nut. Install the rectifier in the center hole near the
rear of the chassis, with the plus

(+)

terminal located
over the tiny indexing hole at position four. Correct
orientation of this rectifier is

essential

for proper wir-

ing.

9 n Select the single fuse clip, and one set of #4 hardware. In-

stall the clip in the right front chassis hole FC, closest to
the foot.

10

0

Select the two dual fuse clips and four sets of #4 hard-

ware. Install these in the pairs of holes FL and FR on
either side of the center of the chassis.

Connect the shorter lead to FC lug
longer lead to the

lower

hole of TS lug

#l.

(S). Connect the

#2.

(S). Note that
lug 2 is the second protruding lug on the terminal strip. It
is

not

the mounting bracket for the terminal strip.
Soldering this lead to the lower hole now will make later
connections to the top portion of the lug easier. Be sure
no stray strands of either line cord conductor are left
unsoldered.

Prepare a

14

clip FL lug
clip FR lug

Prepare a

15

Connect the other end to FL lug

Prepare two 7” white wires. Start with one wire project-

16

ing

6 1/2"

green wire. Connect one end to dual fuse

#l.

Connect the other end to the other dual

#l.

(S).

6 1/2"

white wire, Connect one end to FR lug

#3.

(S).

3/4"

beyond the other, and twist them uniformly

together throughout their length. Connect the project-

ing end to RF lug

of the other wire to

#l.

(S). Connect the corresponding end

RFlug #2.

(S). Place this pair over the

right edge of the chassis.

Prepare two more 7” white wires. Start as before with

170

one wire

3/4"

longer, and twist them together. Connect
the longer end to LF lug #2 (S). Connect the other wire to
LF lug

#l.

(S). Place these wires off to the left.

Prepare an 8” green wire and a 10” white wire. Start

18

0

with the white wire

3/4”

longer than the green wire, and
twist them uniformly together. Connect one end of the
green wire to the lug on black output terminal LB. Con­nect the corresponding end of the white wire to red
terminal LR. (S). Place these wires off to the left.

#3.

11 0

Select the

5-lug

terminal strip and two sets of #4 hard­ware. Install it in the front holes TS, next to the single
fuse clip. Note the position of the mounting lugs (to the
right) in the pictorial diagram.

NOTE: Kits provided with the multiple voltage power transformer

for use in locations outside the United States having a line (mains)
voltage other than 120 VAC are also supplied with an additional two­lug terminal strip which is to be installed using an additional set of
hardware on the other side of the chassis, below the dual fuse clip FL.

#4

12 0 Select the power switch. Install it with the red window to

your right as viewed from the front. The switch snaps
into chassis hole PS from the outside.

13

q

Select the AC line cord and the plastic strain relief.
Separate the two conductors for 2”. Cut 1” off one of the
two leads, and strip

1/4"

of insulation from each lead.
Twist the strands tightly, and tin each end. Make a sharp
'V'

in the cord

8 1/2"

from the longest cut end by bending it
back on itself. Install the relief with the small end nearest
the cut end of the cord. Crimp the two halves of the relief
around the wire at the

'V'

with heavy pliers, to partially
form it before insertion into back panel hole AC. Then
grip the larger diameter with the plier tips, squeeze it
tightly, and insert the cord and the relief from the out-

side. A flat side of the relief mates with the hole shape,

and it snaps into position when fully inserted.