Sherwood R-772 Service Manual page 25

Symptom
FM Failure.
AM Failure.
Stereo Effect Failure.
Stereo does not light up.
Tuner Sound Dead.
1. "L / R" Channel dead.
2. "LEFT" Channel dead.
3. "RIGHT" Channel dead.
Cause and Remedy
A) FM MUTE adjustment inferior.
B) FRONT-END inferior.
C) FM DET COIL inferior.
D) PLL IC check.
1. PLL I.C B+( 5 )V check.
2. PLL control data check. (Data/CE/Clock)
E) TUNER B+ voltage inferior.
F) µ-COM I.C & Resonator inferior.
1. µ-COM I.C B+( 5 )V check.
2. Micom control data check.
A) AM V.T voltage inferior.
B) PLL I.C check.
1. PLL I.C B+( 5 )V check.
2. PLL control data check (Data/CE/Clock)
C) TUNER B+ voltage inferior.
D) AM OSC COIL inferior.
E) µ-COM I.C & Resonator inferior.
1. µ-COM I.C B+( 5)V check.
2. Micom control data check.
A) FM DET COIL Inferior.
B) MPX IC inferior.
1. MPX I.C B+( 14 )V check.
2. MPX control data check.
C) STEREO adjustment inferior.
D) FM MUTE adjustment inferior.
E) µ-COM I.C & Resonator inferior.
1. µ-COM IC B+( 5 )V check
2. Micom control data check.
A) MUTE TR inferior.
B) Connector's disconnection or disjunction.
Change or Close insertion of the connector.
C) AM/FM IF I.C check .
1. Signal IN/OUT terminal.
2. I.C driving voltage check. ( +12V )
D) FM DET COIL inferior.
E) AM IFT COIL inferior.
F) MPX I.C check.
1. Signal IN/OUT terminal.
2. I.C driving voltage check. ( +14V )
24
Ref No.
I.C No. ( 501 )
I.C Pin No. ( 9,10.12,14,15)
I.C No. ( 501 )
I.C Pin No. ( 9,10.12,14,15)
I.C No. ( 501 )
I.C Pin No. (23 )
I.C Pin No. ( 10 )