Philips 7629, Service Manual

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will trigger the power supply to shut down. However, this is a high beam-current
situation, the TV screen will be bright white before the set is shut down.
•
E/W protection , two protection mechanisms are built in, over-current and over-
voltage.
§
In case of over-current due to defective parts in the line deflection output
stage, a high current will flow through resistors 3405//3406.If this current is
large enough to create a voltage drop of 0.7V across 3405//3406,
transistor Q7606 (in A7 diagram) will conduct and pin 80 of the UOC will
be pulled down. Thereafter, the UOC will shut down the power supply. In
case of further current increase, the fused resistor 3411 is built-in for
double protection.
§
In case of a high voltage appearing across capacitor 2401(dependent of
the tube size), which is high enough to trigger zener diode 6401 into
conduction, transistor Q7606 (in A7 diagram) will conduct and UOC is
triggered to shut down the power supply.
•
I
2
C protection , to check whether all I
2
C ICs are functioning.
In case one of these protections is activated, the set will go into ‘standby’.
The ‘on’ and ‘standby’ LEDs are controlled via the UOC.