76FW-53H (serv.man13). DA100 and DW100 training course notes - Sharp TV Service Manual (repair manual). Page 7

Colour Television – DA100/DW100 Chassis

Sharp Electronics (UK) Ltd

Technical Support

September 99

Page 4

N

L

T702

IC708

R763
100

POR701

Q714

From IC702
pin 14

From T701
pin15

D727

R762
220

R768
220

C702
10nF

Degause
Coils

D728
4v7

This circuit is configured to ensure that the degauss circuit will not operated unless the switch mode
power supply is operating and IC702 pin 14 = low.

A positive bias is applied to the emitter of Q714 from T701 pin 15 (rectified by D727 and limited by
D728). Via the opto-coupler; IC708. Since Q714 is a pnp device once the base is taken low compared
to the emitter, Q714 will turn on allowing current to flow through IC708 (LED Section), turning on the
triac T702, allowing current to flow through the degauss coils.

Current will continue to flow through the degauss coils until either the PTC (POR701) has increased in
value sufficiently to cut off the current flow, or IC702 pin 14 goes high, turning of Q714, preventing
current flow through IC708, turning the triac T702 off.

Since the default condition for IC702 = low, it can be seen that the degauss circuit should now operate
each time the CTV is turned on from the main on/off switch or switched from standby to normal
operation. Whether the main processor has set up communication with the slave processor or not.