Realistic STA-115 - Troubleshooting

SYMPTOM
CAUSE AND REMEDY
1
)
No output
Faulty AC
power
cord:
Replace.
Defective
POWE
R
switch
:
Re
pl
ace.
Broken wire in the
power
transformer:
Replace.
Blown
primary
fuse:
Replace.
Defective D701
or diodes,
translstor(s)
in
power
supply
circuit
on
TUNER AUDIO P.C.B.:
Replace
the
defective
part(s).
Main amp
or
temperature
protector
circuit
activated
or
defective:
Deactivate
or
repair.
(1)
12\
(3)
(4)
(5)
(6)
2)
Fuse
blows
(1
)
Defective rectif ier D701 :
Replace.
(2)
Short-circuit in the rectifier circuit:
Remove
the short.
(3)
Short-circuit
in
power
transistor
circuitry TR505
-
512'.
Repair
circuit and/or replace the defective transistor(s).
(4)
Defective
power
transformer:
Replace.
3) A Speakers
do not work.
Speaker selector
switch defective
:
Replace.
Poor
contact in
speaker
output terminals:
Repair
or replace.
Poor
contact in
speaker selector switch:
Repair
or replace.
(1)
(2\
(3)
4) B
Speakers
do
not
work.
(1)
Speaker selector
switch defective:
Replace.
(2)
Poor
contact in speaker selector
switch:
Repair
or
replace"
(3)
Poor
contact in
speaker output terminals
Repair or
replace.
5)
No
output
on one channel with VO-
LUME at maximum and BALANCE at
center, when
a
test
signal
is applled to
the BALANCE control
(VR402)
termi-
nal
of
the non-operating channel.
(1)
Defective
TR401, TR403,
TR601.
TR501 left
channel
(equiv.
Rt.
ch.).
Also
SCR601 and 1C601
:
Replace
the defective
part(s).
(2)
Defective resistor
or
capacitor
of TONE
and
MAIN AMP
circuit
Replace
the
defective
part(s).
6)
No output when a test signal
is
applied
to the
input
terminals.
(1
)
Defective MONO
switch or TAPE MONitor
switch:
Repair
or
replace.
(2)
Defective
SELECTOR switch:
Replace.
7)
No
output when
a
test
signal is applied
to the
PHONO
input
terminals
(1
)
Defective
transistor,
resistor or capacitor
of
PREAMP
circuit:
Replace the
part(s).
(2)
Defective MONO-Stereo
or TAPE
Monitor
switch:
Repair
or
replace.
(3)
Defective
SELECTOR
switch:
Replace.
(4)
Defective
1C301 :
Replace.
8)
DC not
balanced within
l50mV
at
output
of
L/R
channel
(i
)
Defective
TR501, TR503, TR505(L) or TR502,TR504, TR506
(R)
Replace
the defective transistor(s).
(2)
lmproper
value for R503, R511
(L)
or
R504.
R512
(R):
Select suitable
value
resistor.
TROU BLESHOOTING
-33-