Protection - LG GC260W Service Manual

PROPOSAL FOR APPLYING SHORT PROTECTION
• The Contents of Examination
As all the IC that is applied to VCR is controlled by IIC, mutual communication, if Vcc of IC is short or open
with detecting 'Acknowledge' data of the specific IC according to each power(5V, 5VT) µ-COM gets unable to
detect 'ACK' data.
µ-COM regards this case as abnormal one and if it can't detect 'ACK' data for a certain time(3.5 sec) the sig-
nal of 'Power Control' and 'Timer Control' are switched to 'Low'. As a result POWER Switching TR is kept from
generating heat and fire.
Conception
BLOCK Diagram
SLAVE with 5V
SLAVE with 5V
• POWER for each IC
5.2V
5.3VA
• IC to detect 'ACK' data is selected as below because IC is different in accordance to region and option
S/ 5V POWER
Series 5VT POWER
P/Y/I 5V POWER
Series 5VT POWER
5VT SW
5VT SW
Modulator
Hi-Fi IC
NICAM IC
SECAM IC
Power Control
SECAM IC
AVCP IC
*Short protection off mode : DJ01 Diode in
Modulator
AVCP IC
CONTROL
IIC BUS
CONTROL
5.2VT
5.3VA
1-4
TIMER
MASTER
POWER
AVCP IC
TUNER
Timer Control