Realistic STA-78 - Troubleshooting

7.
TROUBLESHOOTING
SYMPTOM
CAUSE,/
REMEDY
1
)
No output
1)
Faulty
AC
power
cord
Replace
the cord.
2)
Defective
POWER
switch
Replace
the switch.
3)
Broken wire in the
Power
Transformer
Replace
the
Transformer.
4) Blown
primary
switch
Replace the
Fuse.
2)
Pilot
Lamp does
not light.
1)
Broken Lamp
Replace the Lamp.
2)
Open
in
the
Power Transformer tertiary winding
Replace
the
Transformer.
3)
Pilot
Lamp
lights but
no
Speaker
output.
1
)
Defective capacitor C802
or
803
Replace
the
defective capacitor(s).
2)
Defective
Rectifier D703
Replace
the
defective
Rectifier.
3)
Defect in the
Power Transformer secondary
winding
Replace
the
Power
Transformer.
4) Blows
Fuse 1)
Defective
Rectifier D703
Replace
the
defective
Rectifier.
2) Short-circuit
in the rectifier circuit
Remove
the
short.
3) Short-circuit
in
Power
Transistor CircLitry
TR611-614
Repair
circuit and/or
replace
the defective
Transistor(s).
5l
"
A"
Speakers
does
not work. 1)
Speaker
Selector
Switch
defective
Replace
the switch.
2l
Poor contact in
Speaker
Output Terminals
Replace
or repair
it.
3)
Poor
contact
in
Speaker Selector Switch
Repair
or replace
it.
6)
"B"
Speakers
does
not work. 1) Speaker
Selector Switch defective
Replace
the switch.
2)
Poor
contact
in
Speaker Selector Switch
Repair
or replace
it.
3)
Poor
contact
in
Speaker
Output
Terminals
Repair
or
replace it.
7)
No
output one
channel with VOLUME
at
maximum
and
BALANCE at
center,
when
a
test signal
is
applied to
the
terminal of non-operating
channel of
the
BALANCE control
VR502.
1)
Defective
Transistor TR501-503
or
TR601-618
Replace the defective
Transistor(s).
2)
Defective resistor or capacitor of
TONE
and
MAIN AMP circuit
Replace the defective
part(s).
8)
No
output when a test signal
is applied to
the
input
terminals,
except
PHONO
input.
1)
Defective MONO-Stereo or
TAPE
MONitor
Switch
Repair
or
replace the
Switch.
2)
Defective
SELECTOR
Switch
Replace the
Switch.
9)
No
output
when
a test
signal is applied to
the
PHONO
input
terminals.
1)
Defective
transistor,
resistor
or
capacitor of
PRE
EO AMP circuit
Replace
the
part(s).
2)
Defective MONO-Stereo or
TAPE
switch
Repair
or
replace
the switch.
3)
Defective
SELECTOR
Switch
Replace
the SELECTOR
Switch.
-13-