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TROUBLE
SHOOTING
CHART
SYMPTOM
CAUSE
REMEDY
Amplifier causes
power
line
fuse to
blow.
Line cord, J8, J9, primary
or
high voltage
secondary windings
of Tl, Incorrectly wired.
Prt./h.v.
sec.
windings of
Tl shorted.
(If
the amplifier causes the
line
fuse to
blow
again
when
connected
to
the
line
with
5U4
GB
rectifier
V7
removed, one
or the other of the
above
causes must
be
the reason.)
V7
shorted
replace
after
checking
C26
V7
filament not
lit.
Incorrect
wiring
of
fll.
leads
to
V7
socket.
repair
5V
fll.
winding
of
Tl
open.
replace
Tl
Any
or
all
other tube filament
Open
lead from
6.3
V
winding
of
Tl
.
repair
not
lit.
6.3
V
winding
of
Tl
open.
replace
Tl
DC
voltage
at
V7
cathode
(pin 8)
Is
Incorrect as specified
below.
*
*
a)
No
voltage
Defective
V7
replace
C26
A
shorted Internally or externally.
replace or
repair
b)
High Voltage
Connection
to
C26
A
from pin
8
of
V7
broken.
i
repair
Connection
to
center tap of
h. v. sec.
winding
of
Tl
open.
repair
Output
tubes
V5
&
V6
over-biased or not
draw
-
Ing current.
see trouble-shooting
typical
i
c)
Low
voltage
Excessive current drain
In
amplifier.
see
trouble-shooting typical
j
Defective
V7.
replace
Connect a phonograph and
speaker
to
the amplifier as described
In "Electrical
Connections"
and
set controls for
phono
list-
ening.
Play a
known
high quality
LP
recording
on
the
phonograph.
If
there
Is
no
output
to
the speaker
or
If
the output
Is
low
or
audibly
distorted,
procede
to
the
checks
for
those
symptoms.
If
there
Is
excessive
hum
In
the output, disconnect the
phono
Input
cable from
the amplifier
and
short the
phono
Input |ack
to chassis.
If
the
hum
disappears the trouble
Is
not
In
the amplifier but
In
the
phonograph
or
In
the
connection
to
the amplifier.
The
cause of phonograph
hum may
be
a metal pick-up arm
not
grounded
to
the
cable
shield
(try
a good
single
ground con-
nection
to
the
cable
shield
from
turntable
frame, pick-up arm,
and
cartridge case), direct
hum
pick-up by
the
magnetic
car-
tridge
from the record player motor
(try
using
a
rubber
mat
on
the turntable
to
Increase the separation of the
pick-up
from
the motor), or
pick-up
from
a power
transformer or other
magnetic
field In
the vicinity
(try
moving phonograph
away
from
suspected
source)*
Check
also that the
phono
Input
cable
shielding
Is
grounded
to
the amplifier
chassis at
one
point
only
through the
skirt
of the Input connector
where
It
plugs
Into
the amplifier.
Finally,
try
a
good
building
ground such
as
a
connection^ from
a
cold
water ptpo
terminated under speaker
terminal
"G"
on
the amplifier.
Do
not
connect
such a ground
wire
to
other
components
In
the system.
Excessive
hum
on
other
Inputs
may
be checked
In
a
similar
manner.
Disconnect
the Input
cable
In
question
and
short the
pwtlcular
Input fack
to
the
chassis.
If
the
hum
disappears, the trouble
Is
external
to
the amplifier.
Note
that
on
all
Inputs,
the
braid of
the Input
cable should connect
to
the amplifier only through the
skirt
of the Input connector.
The
cause
and
remedies
for
the following
symptoms
are then based
on
the assumption that
checks
made
In
the
manner
described
above have
eliminated the
possibility
of the trouble
being
external
to
the amplifier.
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