Troubleshooting - Sherwood R-725/RDS Service Manual

TROUBLESHOOTING
Symptom Cause and Remedy
Receiver inoperative. A) Faulty AC power cord.
(FL indicator does not light.) Replace.
B) Defective the power switch.
Replace.
C) Broken wire in the power transformer.
Replace.
D) Blown fuse.
Replace the fuse.
A) Defective power transformer.
Replace.
B) Short on the primary or secondary of the transformer circuitry.
Repair the short.
C) Damaged rectifier D105-D112 or damaged transistor
Q215L/R/C/SL, Q216L/R/C/SL.
D) Short circuit in the amplifier circuit.
Repair the shorted component(s) in the amplifier circuit.
A) Defective in transistor Q215L/R, Q216L/R on the AMP302 Biard.
B) Pulled out of correct speaker swithch.
Fuse blows when power is turned on.
Power indicator lights but no sound from
both channels.
One channel does not work when volume
is at maximum with a test signal applied to
the center terminal of volume control of the
dead channe.
A) Defective in transistor Q215L/R or Q216L/R on the AMP302 Board.
Replace the defect.
B) Break in copper foil of printed circuit board.
Repair the defect.
C) Short in speaker output terminal.
Repair or replace.
A) Headphone plug does not match with jack.
Replace the jack.
B) Defective resistor R701U/R.
Replace.
A) Defective front-end (FE).
Replace.
B) Defective FM switch.
Replace the switch.
C) Defective transistor Q3 and ICS (IC2,IC3).
Replace the defective transistor or IC(s).
D) Defective coil T4, T5.
Replace the coil(s).
E) Defective lead-in.
Repair or replace the lead-in.
F) Ceramic filters CF 1, CF3 defective.
Replace the defective ceramic filter(s).
A) Improper adjustment.
Readjust VR3.
B) iC3 defective.
Replace.
C) Variable resistor VR3 defective.
Replace the variable resistor.
A) If volume from both L and R channels is not loud enough :
Front end section defective.
Faulty |C2, Coil T4 or T5.
If sound of one channel is not loud enough : Defective VR3.
Speaker works normally but headphones
inoperative.
FM inpoerative
Poor multiplex separation.
FM volume is insufficient.
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