Troubleshooting - Sherwood RX-4109 Service Manual

Symptom
Power On Failure.
1. FLT does not light up.
2. ST-BY LED does not light up.
Fuse Disconnection.
(Power On)
Key Disorder.
Power Off in 2~3 sec.
after Power On.
Bump Sound.
( During Input-Select Switch's change. )
Sounds from Speaker.
when Headphone's connected .
Bass Control Failure.
Treble Control Failure.
AMP Sound dead.
1. L / R Channel dead.
2. LEFT Channel dead.

TROUBLESHOOTING

Cause and Remedy
A) AC-Cord check.
B) Power Trans ( Main/ST-BY ) check.
C) Fuse's disconnection check.
D) Connector's disconnection or disjuction.
Change or close insertion of the connector.
E) Inferior Stany-By switch.
F) µ-COM I.C & Resonator check.
1. µ-COM IC B+( 5 )V check.
2. µ-COM clock pulse check.
A) Inferior transformer.
B) AMP Drive Transistor out ( POWER TR )
C) AMP Drive I.C out ( POWER TR )
A) KEY's being pushed check.
B) KEY Signal input components inferior.
C) KEY data check.
D) µ-COM I.C or Resonator inferior.
1. µ-COM IC B+( 5.5 )V check
2. µ-COM clock pulse check.
A) Drive I.C out ( POWER TR )
B) Drive Transistor out ( POWER TR )
C) Protection circuit check.
1. Output DC check.
2. µ-COM I.C protection terminal check.
D) Posistor's connector disconnectoin.
A) POWER MUTE transistor's out and inferior.
µ-Com Front Mute Control PORT check.
A) HEADPHONE JACK connection inferior.
B) µ-Com I.C inferior.
1. µ-Com H/P IN/OUT control "PORT"check.
A) TONE VOLUME IC check.
1. Signal IN/OUT terminal.
2. IC voltage check ( +10 )V
3. IC control data check.
A) Signal Mute TR's inferior.
B) Connector disconnection & disjunction.
Changer or close insertion of the connector.
Ref NO.
FUSE ( 501 )
CP ( 503 )
SW ( SW401 )
I.C Pin No. ( 72 )
X-TAL( 401 )
Q ( 306L/R, 307L/R )
Q ( 305L/R )
SW ( 401 ~ 410 )
R ( 427 )
I.C Pin No.( 35, 36 )
I.C No. ( 401 )
I.C Pin No. ( 89 )
X-TAL ( 40 )
Q ( 306L/R, 307L/R )
Q ( 305L/R )
R ( 537, 532 )
I.C Pin No. ( 24 )
CP ( 210 )
Q ( 315, 314L/R )
I.C Pin No. ( 31 )
JACK ( 1 )
I.C Pin No. ( 25 )
I.C Pin No. ( 7, 31 )
I.C Pin No. ( 35 )
I.C Pin No. ( 1, 2, 36 )
Q ( 319, 314L/R )
CP ( 401 )