Installation; Using The Amplifier With Other Preamplifiers - Heath Heathkit W4-AM Assembling And Using

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
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