Philips Colour Television Service Manual page 82

EN 82 9. DPTV585 AA
9.2.2 AC Input Board
The AC Input circuit is located on the AC Input panel. AC power
is connected to the AC Input panel via connector 1505. A 6.3
Amp Fuse, 1506 provides overcurrent protection. The Neutral
side of the AC line is connected to a series of Spark Gaps,
1529, 1530, and 1531 to the Tuner Ground to protect the set
from voltage surges. AC voltage is fed to Bridge rectifiers 6500
9.2.3 Standby Power Supply
When power is applied to the set, Capacitor 2533 begins
charging via startup Resistor 3527. When the voltage on Pin 4
of 7510 reaches approximately 19 volts, the IC begins
switching Pin 1 of 7510. When Pin 1 goes Low, current flows
through the windings of 5501 via Pins 8 and 6. Energy is
coupled to the secondary windings. Operating voltage for the
Standby supply after startup is supplied by windings connected
to Pins 2 and 3. The +5STDBY is the reference supply for the
regulation circuit. The +5STDBY supply is fed to the input of
Shunt Regulator 7516 which drives Optoisolator 7511. If the 5-
volt supply
Circuit Descriptions, List of Abbreviations, and IC Data Sheets
Figure 9-2 AC input board
Figure 9-3 Standby power supply circuit
and 6402. Bridge 6500 provides the RAW B+ to the Main
Power supply located on the LSB. The Neutral side of the AC
line is also connected to the STARTUP for the Main supply.
This provides the Startup voltage for the Main supply.Bridge
6502 provides the Raw DC for the Standby supply.
increases, 7511 will turn on harder, reducing the feedback
voltage on Pin 6 of 7510. If the 5 volt supply decreases, the
voltage on Pin 6 will increase, causing the internal switch of
7510 to stay on longer.
Over voltage protection is accomplished by monitoring the
voltage on Pin 5 of 7510. Voltage from Pin 2 of 5501 is rectified
by Diode 6511 and is fed to Pin 5 via diode 6514. If this voltage
goes above a certain level, 7510 will turn Off. If the DC voltage
feeding 7510 decreases, the Feedback voltage on Pin 6 will
increase. To prevent the IC from being overdriven, the voltage
on Pin 6 is limited to 5 volts. In normal operation, DC from the
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