Sherwood RX-772 User Manual download pdf (Page 13)

Ref No.

Power On Failure A) AC-Cord check.

1. FLT does not light up. B) Power Trans (Main/ST-BY) check.

2. ST-BY LED does not light up. C) Fuse's disconnection check. F 501

D) Connector's disconnection or disjunction. CP(500, 503)

Change or close insertion of the connector. FPC101

E) Inferior ST-By switch. SW501

Fuse Disconnection. A) Inferior transformer.

(Power On) B) AMP drive transistor out. (POWER TR) Q306(L, R), Q307 ( L, R )

C) voltage check.

1. B+ ( 55 )V, B- ( 55 ) V

Key Disorder. A) Key's being pushed check.

B) Key signal input components inferior.

C) Key data check. I.C201 Pin No. ( 49 )

D) μ-COM I.C201 or Resonator inferior.

1. μ-COM IC B+( 5 )V check.

I.C Pin No. ( 15, 16 )

2. μ-COM clock pulse check.

I.C Pin No. ( 10, 11 )

Power Off in 2~3 sec. A) Regulator I.C out.

after Power On. 1. Signal IN/OUT check.

B) Drive transistor out. ( POWER TR ) Q306 ( L, R ), Q307(L, R)

C) Protection circuit check.

1. Output DC check. Q512

2. μ-COM I.C protection terminal check.

u-COM IC201 Pin No. ( 1 )

3. Posistor's disconnection check. CP507

D) Connector's disconnection or disjunction CP502

E) SLEEP MODE cancellation.

Bump Sound A) SPK Mute transistor's out and inferior. Q ( 316L, 316R , 318L, 318R)

(During input-select switch's change.)

μ-Com front mute control PORT check.

IC201 Pin No. ( 28 )

Sounds from Speaker when A) HEADPHONE JACK connection inferior. JK302

Headphone's connected. B) IC 201(µ-Com) inferior.

1. IC201 H/P RLY control "PORT" check. Pin No. (5)

Bass / Treble Control Failure. A) VOLUME I.C check.

1. Capacitor correction figure check. C(135L, 135R, 154L, 154R)

C(136L, 136R)

2. Signal IN/OUT terminal check.

3. I.C104 voltage check. ( +6.8 )V, ( -6.8 )V I.C PIN No. ( 37, 38 )

4. I.C104 CLK/DATA I.C PIN No. ( 15, 14 )

TROUBLESHOOTING

Cause and RemedySymptom

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Sherwood RX-772 User Manual Page 13

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