Eico ST 40 - Troubleshooting Chart

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