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STOP
TROUBLE-SHOOTING CHART
PAGE
13
SYMPTOM
CAUSE
REMEDY
Amplifier causes
power
line fuse
to
blow.
Power
line
fuse
blows
again with
VI
1
out of
its
socket.
Line cord, J16, primary or high voltage
secondary windings
of
T3
shorted Infern-
ally or externally
(wiring).
Replace
or repair.
Amplifier causes
power
line fuse
to
blow.
Power
line fuse
does
not
blow again with
V
1
1
out of
Its
socket.
Defective
Vll, C35,
V7/V8,
V9, V10;
T1
or
T2
primary shorted
internally or
externally.
Replace
or
repair.
Any
or half
of tube filaments not
lit.
Open
tube
filament.
Open
lead from
one
of the
6.
3V
windings
of T3.
One
6.
3V
winding
of
T3 open.
Replace
or
repair.
^Output
tube bias too high
(resulting In distorted
output
waveform).
""
M
°
Open
R73, R74.
Replace or
repair.
DC
voltage
at
VU,
cathode
(pin
8)
Is
Incorrect as specified
below.
a)
No
voltage.
Defective
VI
1.
C35
shorted Internally or externally.
Replace
Replace
or repair.
b)
High
voltage.
Connection
from
C35
to
pin
8
of
V
11
Is
broken.
Connection
to
center
tap of
h.v.
secondary winding
of
T3
open.
Output
tubes,
V7,V8,V9, VI 0
over-biased
or not
drawing
current.
May
result
from
open
R73, R74,
Repair
Check
possible
causes
and
replace
or repair.
Check
possible
causes
and
repair.
c)
Low
voltage.
Excessive current drain
In
amplifier.
Defective
VI
1
See
trouble-shooting typical
stage.
Replace
Excessive
hum
on mag.
phono
tape
head
or mic.
VI
or
V2
defective
FIl.
leads dressed too close
to grid
lead.
Tube
shield
not
making
electrical
contact
to
base
or
base not
making
electrical
contact
to chassis.
Shielding
and grounding
of wiring
to
Input
Jacks not
exactly
as Instructed
and shown
in
drawings.
Replace
Dress
fil.
leads
away
from
grid lead.
Check
and
correct.
Correct.
Excessive noise
on mag.
phono
or
tape
head.
VI
and
V2
and
contacts
dirty.
Clean
thoroughly with carbon
tetrachloride.
Sustained
oscillations.
Poor
dress
of output transformer T1 or
T2
leads.
Dress
all
input leads
and
Tl,
T2
leads
away
from
each
other.
Keep
Tl,
T2
leads
away
from Input
jacks.
Sustained
microphonics
on mag.
phono, tape
head
or mic.
VI
or
V2
defective.
'
Replace
Hum
on
all
Inputs
V3
or
V4
defective, not properly shielded,
or
dirty sockets
and
contacts.
Dress of
power
transformer
T3
leads.
Replace,
correct,
or clean.
Correct
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