76FW-53H (serv.man13). DA100 and DW100 training course notes - Sharp TV Service Manual (repair manual). Page 22

Colour Television – DA100/DW100 Chassis

Sharp Electronics (UK) Ltd

Technical Support

September 99

Page 19

The outputs from all of the audio output stages are fed to the base of Q303 and Q304. C377 and
R361 form an averaging circuit. Since the audio signals are basically sine waves the d.c. voltage at
the base of these transistors
should be zero. If this base
voltage was to increase in a
positive direction Q303 will turn
on, removing the biased from
IC1001 pin 95, and the CTV will
switch to standby.

The same is true if the base
voltage increase negatively, this
time Q304 will turn on, turning
on Q302 causing IC1001 pin 95
to fall and the CTV will again
switch two standby.

If the beam current increase D622 will conduct, turning on Q606 which removes the bias from IC1001
pin 95. The CTV will switch to standby

During the boot sequence the horizontal drive is inhibited by the HOUT signal from the
microprocessor (IC1001 pin 57).

Its function is to remove the line drive by turning on Q607, thus placing short between the horizontal
drive signal and ground, at the same time this HOUT pulse will cause the audio mute circuits to
activate, preventing any noise from the speakers.

Additionally HOUT signal will occur when the microprocessor can not communicate with the other
devices connected to the I²C buses

Protection
IC1001 pin 95

-16v

Audio

+5v

Q303

R1021
4k7

Q302

Q304

D301

R361
10k

C377
10

R360
10k

Q606

D622
27v

R615
5k6

C644
2200

ABL
(T601 pin 8)

1

2

3

100nF

5v

C1028

IC1005

Main
Reset

HOUT
IC1001 pin 57

3v3

Mute

Q1004

R1047
10k

R1049
10k

R1044
10k

R1005
4k7

C1033
68nF

3v3

D1009

R626
4k7

Q602

Line Drive