Main Ic's Key Test Point (Reset Circuit) - THOMSON 50M14DP Service Manual

3.19 Main IC's key test point (Reset circuit)
12V will charge to C957 (Capacitance is short circuit in the period of charge) when
system is power on.Q905's B and E is in same level. Dynatron is cut‐off. C pole is in
low level. When C957 is full (Capacitance is same to open circuit), Q805's B is 0.7v or
more small than E's level. Dynatron is break‐over. C pole will output high voltage level.
Main IC request the RESET time is more than 10S. Q906 is designed to prevent
system reset in standby. If there has no Q906 (RESET signal will be plugged to high
level in normal work or even in standby), 24V will drop in standby and Q905's C will
follow it, so the system will reset.
RESET signal
Power on reset Power off reset
The C pole of Q905 is
RESET test point.
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