Read Sharp 32JF-74H (serv.man2) Service Manual online
50Hz Widescreen Colour Television – GA20 Chassis
Sharp Electronics (UK) Ltd
Technical Support
Issued June 02
Page 14
M
UTE
Power On
During start-up IC1001 pin 59 is high, which turns on Q1305 removing 5v from IC1301 and IC1302
(audio outputs) pin 12. Once the start-up is complete Q1305 turns off allowing the voltage at pin 12 of
IC1301 and IC1302 to rise to 5v.
During start-up IC1001 pin 59 is high, which turns on Q1305 removing 5v from IC1301 and IC1302
(audio outputs) pin 12. Once the start-up is complete Q1305 turns off allowing the voltage at pin 12 of
IC1301 and IC1302 to rise to 5v.
R1074
39k
D1016
R1082
12k
R1083
12k
R1307
27k
D1019
R1304
100R
Q1305
R1317
22k
R1081
1k8
D1017
R354
4k7
R355
4k7
R312
4k7
R314
4k7
D1018
D1303
R1322
1k
Q1301
D1302
C1314
330µF
R1308
10k
IC1001
Pin 85
LED
5v
Standby
5v
Standby
5v
LED
5v
R1316
27k
IC1301
Pin 12
IC1302
Pin 12
IC1001
Pin 95
5v
Q303
Q304
Q305
Q306
SC2 Out
Right
SC2 Out
Left
SC1 Out
Left
SC1 Out
Right
R1318
22k
IC1001
Pin 59
Q1012
Power Off
To ensure that no noise can be heard from either the loudspeakers or the auxiliary outputs there are
three power off mutes. When the green section of the LED is turned off D1016 is forward biased
reducing the the base voltage of Q1012, allowing Q1012 to turn on.
To ensure that no noise can be heard from either the loudspeakers or the auxiliary outputs there are
three power off mutes. When the green section of the LED is turned off D1016 is forward biased
reducing the the base voltage of Q1012, allowing Q1012 to turn on.
Off-Mute1
Q1012 turns on and forward biases D1017 which will take IC1001 pin 95 high. This ensures that the
line oscillator is turned off, therefore, there will no possibility of any supplies from the line stage that
could possibly cause noise.
line oscillator is turned off, therefore, there will no possibility of any supplies from the line stage that
could possibly cause noise.
Off-Mute 2
Q1012 turns on and forward bias D1018 which in-turn will turn on Q303, Q304, Q305 and Q306. each
of these transistors are connected between one of the auxiliary outputs and ground, therefore no
signal or noise can pass.
of these transistors are connected between one of the auxiliary outputs and ground, therefore no
signal or noise can pass.
Off-Mute 3
This is similar to the power on mute with exception that it is triggered via Q1012 instead of IC1001
pin59
pin59
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