Harman Kardon HK20 User manual

MODEL HK20
POWER AMPLIFIER
INSTRUCTION MANUAL
It
is
essential
you
read
this
instruction
booklet
carefully
before
installing
your
high
fidelity
system.
You
have
invested
in
an
extremely
fine
electronic
instrument
into
which
many
excellent
engineering
developments
have
been
incorporated,
and
each
is
important
for
the
proper
operation
of
your
system.
This
booklet
has
been
written
in
simple
non-technical
language
and
if
you
will
take
time
to
read
it
first
before
doing
anything
else,
you
will
find
it
simple
to
obtain
optimum
performance
from
your
Harman-Kardon
Amplifier.
Be
sure
to
keep
this
booklet
available
at
all
times.
It
contains
indispensable
technical
and
service
information.
UNPACKING
After
unpacking
the
HK20,
inspect
it
carefully
for
signs
of
transit
damage.
The
unit
was
subjected
to
many
inspections
and
tests
prior
to
final
packing,
and
it
therefore
should
be
in
perfect
condition.
If
damage
is
visible,
notify
your
dealer
at
once.
If
the
unit
was
shipped
to
you,
notify
the
transportation
company
without
delay.
Check
the
contents
of
the
carton
thoroughly
and
inspect
the
folds
of
the
packing
material
before
discarding
it.
Your
package
should
contain
the
following
items:
1
Model
HK20
Basic
Power
Amplifier.
1
Instruction
Booklet.
1
Warranty
Card.
WARRANTY POLICY
We
urge
you
to
completely
fill
in
your
warranty
card
and
mail
it
to
the
fac-
tory
without
delay
to
protect
your
rights
under
warranty.
The
warranty
cards
-are
carefully
filed
for
reference
and
should
you
require
information
on
the
use
of
this
high
fidelity
unit,
or
repair
service,
we
will
be
able
to
immediately
identify
your
set
and
reply
quickly.
NOTE:
It
is
necessary
to
receive
factory
authorization
before
returning
a
set
for
warranty
repair
either
to
the
factory
or
to
an
authorized
station.
Repairs
are
to
be
returned
on
an
Express
Prepaid
basis.
A
letter
describing
the
exact
diffi-
culty
must
be
enclosed
with
the
unit.

WARRANTY
We
warrant
each
Model
HK20
to
be
free
from
defects
in
material
and
workmanship
under
normal
use
and
service,
and
in
accordance
with
the
condi-
tions
herein
below
set
forth,
for
a
period
of
1
year
from
date
of
delivery
to
the
original
purchaser,
and
agree
to
replace
or
repair
any
part
or
parts,
with
the
exception
of
tubes
which
are
under
the
manufacturer's
90
day
warranty,
returned
to
us
within
said
1
year,
with
transportation
prepaid
and
which
our
examination
shall
disclose
to
our
satisfaction
to
have
been
thus
defective.
This
warranty
does
not
include
free
labor,
nor
is
it
applicable
to
any
instrument
which
shall
have
been
repaired
or
altered
in
any
way
so
as
in
our
judgment
to
affect
its
stability
or
reliability
nor
which
has
been
subject
to
neglect,
misuse,
abuse,
negligence
or
accident
nor
which
has
had
the
serial
number
altered,
effaced,
or
removed.
Neither
shall
this
warranty
apply
to
any
instrument
which
has
been
connected
otherwise
than
in
accordance
with
instructions
furnished
by
us.
This
warranty
is
expressly
in
lieu
of
all
other
warranties,
express
or
implied,
and
of
all
other
obligations
or
liability
on
our
part,
and
we
neither
assume
nor
authorize
any
representative
or
other
person
to
assume
for
us
any
other
liability
in
connection
with
the
sale
of
this
instrument.
USING THE HK20 POWER AMPLIFIER
INSTALLATION PROCEDURE
Ventilation:
The
unit
is
well
ventilated
in
itself,
but
sufficient
space
must
be
allowed
around
it
to
permit
proper
air
flow.
Install
the
amplifier
in
a
manner
to
allow
for
unrestricted
circulation.
Do
not
place
books
or
other
objects
on
the
cage
or
in
the
immediate
vicinity
of
the
instrument.
Reducing
the
air
flow
will
result
in
sharply
reduced
component
and
tube
life.
Power Requirements:
Plug
the
AC
cord
into
any
outlet
furnishing
117
volts
50
or
60
cycle
AC
cur-
rent.
The
voltage
may
vary
between
105
and
125
volts.
REAR PANEL CONNECTIONS
SPEAKER
(I7VAC-60% ~ 16
Liles
INPUT
com
8
16
) LEVEL
s
(@)
CONTROL
G)
QZ
Q
(
| ‘y A. 3AG
REAR PANEL MODEL HK20
Connecting Your Speaker:
The SPEAKER OUTPUT terminal strip is located on the rear of the chassis.
lf you are using an 8 ohm speaker connect one speaker lead to the 8 ohm termi-
nal and the other lead to COM. For a 16 ohm speaker connect one speaker lead
to the 16 ohm terminal and the other lead to COM.

Input Connection:
To
connect
your
HK20
to
a
monaural
preamplifier
attach
the
shielded
cable
supplied
with
the
amplifier
between
the
INPUT
jack
on
the
HK20
and
the
out-
put
jack
on
the
preamplifier.
If
you
are
connecting
the
HK20
to
the
AX20
con-
verter
connect
the
shielded
lead
between
the
HK20
INPUT
jack
and
the
LEFT
PREAMP
OUT
jack
on
the
AX20.
Input Level Control:
This
control
adjusts
the
gain
of
the
HK20
power
amplifier.
For
monaural
application
it
should
be
set
to
maximum.
For
stereo
use
it
is
set
to
balance
your
other
amplifier.
When
used
in
conjunction
with
the
Harman-Kardon
AX20,
the
INPUT
LEVEL
control
should
be
used
in
the
following
manner.
1.
Turn
the
INPUT
LEVEL
control
on
the
HK20
to
zero.
9.
Turn
the
volume
control
on
your
AX20
to
normal
listening
level,
and
set
the
balance
control
to
the
mid-position.
3.
Play
a
stereo
record
or
tape.
The
left
channel
should
be
completely
in-
operative
since
the
INPUT
LEVEL
control
on
the
HK20
is
set
at
zero.
4.
Slowly
rotate
the
HK20
INPUT
LEVEL
control
until
the
left
channel
perfectly
balances
the
right.
5
Allow
the
INPUT
LEVEL
control
to
remain
set
in
this
position.
Further
adjustment
should
not
be
necessary.
All
additional
channel
balancing
should
be
made
with
the
balance
control
on
the
AX20
converter.
ADJUSTMENTS
Hum Adjust Control:
This
control
is
accessible
from
the
underside
of
the
chassis
with
the
bottom
plate
removed
and
from
the
top
of
the
unit
with
the
cage
removed.
It
is
physi-
cally
located
between
the
EZ81
rectifier
tube
and
the
6CG7.
To
adjust,
allow
the
amplifier
to
thoroughly
warm
up.
Disconnect
the
input
from
the
preamplifier
stage
and
turn
the
INPUT
LEVEL
control
to
maximum.
While
listening
to
the
hum
level
in
your
speaker,
turn
the
HUM
ADJUST
con-
trol
for
minimum
hum.
Output Tube Balance Control:
The
BALANCE
control
is
accessible
from
the
underside
of
the
chassis
with
the
bottom
plate
removed
and
from
the
top
of
the
unit
with
the
cage
re-
moved,
it
is
physically
located
between
the
EL84
output
tubes.
This
control
is
preset
at
the
factory
and
should
not
be
touched
unless
the
output
tubes
are
changed
or
a
periodic
yearly
check
is
required.
When
adjustment
is
necessary
follow
the
outlined
procedure.
1.
Turn
the
INPUT
LEVEL
control
on
the
HK20
to
minimum.
2,
Remove
the
shielded
connecting
cable
from
the
INPUT
jack.
3.
Slowly
rotate
the
OUTPUT
TUBE
BALANCE
control
for
minimum
hum
in
your
speaker.
4.
If
the
hum
level
is
inaudible,
set
the
OUTPUT
TUBE
BALANCE
con-
trol
to
the
exact
center
position.
5,
For
those
who
demand
supercritical
adjustment
of
this
control,
the
adjustment
should
be
made
with
an
IM
analyzer.

6CG7
V1
.05/400V
SOOK
LEVEL
CONTROL
RV2472952
220K
R7
1.5K "
= =
% RESISTANCE CHART
tee fae dos es |e eee
~iom| o_[rse [iso [180 tw wf aan |
470K 150 | 150_| 150 >500K
iwecer_[ avon] iso [iso igo_| cog) Sw
veezei [es | | >mliso jo] | es | |_|
*% LEVEL CONTROL MIN. GAIN
NOTE:
UNLESS OTHERWISE SHOWN
ALL RESISTORS 1/2 WATT 410%
ALL CAPACITOR VALUES WITH DECIMAL TO BE PAPER iN MFD
ALL CAPACITOR VALUES WITHOUT DECIMAL TO BE GENERAL
PURPOSE CERAMICS SOOWVDC IN MMF
ALL VOLTAGES ARE DC
ALL RESISTANCES ARE IN OHMS
$247
S$ 24730184
|
| [C40 |
JE220297
C4a=40MF
C4b=40MF
C4c=100MI
Rel
100
HUM
ADJ.
RVCOM2E

R13
68K
.05/600V ewes
=
340V
5
50-20%
oF
c2 Rg Ris
470K
FT2202785
20%
BLU/WH icaey eee
RIO
BALANCE
ae
RVCOM2569
REO/BLU
aa
== !00 270-1W
G
RII
470K
0%
RIS
.05/600V
— 220-20%
: | Jz [HOW YY
. EL84 \ co S75V
. 6BQ5
RI2 R20 >39-Iw
R22
ae sear ee al
| JE2202842 |
4b
Cac
C5a:40MFD.-450V.1
|[C5b
C50}
|;
op cent C5b=50MFD ~—350v, LL — =e |
} oh —
= 300V.
-300V.
D.-25V.
BROWN T2
|| FT2202784
BROWN/WH ©
1 1/2 A-3 AG
39
BLK/WH
BLK
H7VAC-60%

Audio
Circuits:
Output Level:
Peak Power Output:
Output Impedance:
Frequency Response:
Damping Factor:
Hum:
Sensitivity:
Fuse:
Tube Complement:
Dimensions:
Power Consumption:
Shipping Weight:
SPECIFICATIONS
2 - EL84’s self biased, pentode connected in push-pull.
20 watts at less than 1% harmonic distortion.
17 watts at less than 0.5% harmonic distortion.
5 watts at less than 0.2% harmonic distortion.
17 watts at less than 2% intermodulation distortion.
Harmonic distortion readings at 1000 c.p.s.; Inter-
modulation distortion readings at 60/6000 c.p.s.; 4:1;
All at 16 ohm load—120 volts
40 watts.
8 and 16 ohms,
+ 0.5 db 15-30,000 c.p.s. at 1 watt.
+ J.0 db 20-20,000 c.p.s. at 15 watts.
Ol
90 db below 20 watts.
0.5 volts
Externally accessible
(Total 4) 1-EZ81, 2-EL84, 1-6CG7
107 wd" h, x4" d.
60 watts
14 Ibs.

MAINTENANCE AND REPAIRS
Fuse:
In
the
event
of
a
potentially
damaging
failure
of
tubes
or
components,
the
Model
HK20
is
protected
by
a
1%
ampere,
type
3AG
fuse,
located
on
the
rear
of
the
unit.
If
this
fuse
is
blown,
it
should
be
replaced
only
with
one
of
the
same
rating.
Replacing
with
a
fuse
of
higher
rating
will
not
protect
the
amplifier,
and
may
result
in
severe
damage,
which
will
not
be
covered
by
the
factory
warranty.
Routine Maintenance:
Due
to
the
conservative
design
and
high
quality
componets
of
the
Model
HK20,
no
routine
maintenance
other
than
yearly
tube
checking
is
advised.
Oc-
casional
resetting
of
the
hum
and
output
balance
adjustments,
following
the
procedure
described
above,
will
keep
the
unit
operating
at
peak
efficiency.
These
adjustments
should
certainly
be
made
after
any
tube
replacement.
Repair:
Only the most qualified service technician should be employed, as special
equipment and training is required to properly service a high fidelity amplifier.
This manual contains information of great value to the repairman, and should
be kept available.
Factory Warranty Stations are maintained in most major cities. For the ad-
dress of the nearest one, or for any other information relating to your Harman-
Kardon products, write to the attention of the Customer Service Department,
Harman-Kardon, Inc., 520 Main St., Westbury, N.Y. Be sure to include the model
and serial number of the set in question. A short description of your complete
installation is often of help in answering your questions.
LIST OF REPLACEABLE PARTS
Part No. Description List Price
ZCOM2953 Fuse 10
RVCOM2569 | Balance Control | 60
RV2472952 Level Control .90
JE2202842 Electrolytic 3.00
JE2202974 Electrolytic 3.00
FT 2202784 Power Transformer 14.75
FT 2202785 Output Transformer 15.00