[2]
In addition to the Standby and Main power supplies, there is a Low B supply too. The Low B audio Out module shown below generates another four sources.
The Audio Output IC [Q610] is mounted on a heat sink on the upper left side of the PCB assembly. The Low B power supply areas consisting of {Q820, Q829, Q835 & Q870} occupy the reminder of the PCB.
Q835 & Q870 are switching regulators, and should be treated as such if servicing them and their associated circuitry.
The 5V Standby source from the Power Supply Board is used to enable the TV microprocessor and other sections of the signal board, when the unit is OFF. Next is a junction of two protection inputs. Pin-13 of P807 is directly connected to Pin-7 of P808 on the Power Supply. This protect input is from the Power Supply microprocessor and the other is from circuits monitoring the voltages generated on the Low B board.
The Power Supply microprocessor monitors the voltage generated by the Main Power Supply and if they are abnormal the protect line originating at the Power Supply Microprocessor will go High, causing shut down and an error code. {Power :LED Flashes in (0.5) seconds intervals.}
If a voltage generated on the Low B audio board should become excessive, the protect line originating on the board itself will rise, causing shut down and an error code. {Power LED Flashes in 0.5 seconds intervals}.
To effect shut down when one of these lines rise, they are both coupled to the Gate of an SCR [D819] as a protect line. A High on this line causes the SCR to couduct, Pulling the Power On line from the TV microprocessor Low, and placing the unit to latching shut down state.
When the Power On line is pulled Low, except for Standby 5V sources, the power supply microprocessor will shut the sources generated by the main Power Supply down in the proper sequence.
Contd:
In addition to the Standby and Main power supplies, there is a Low B supply too. The Low B audio Out module shown below generates another four sources.
The Audio Output IC [Q610] is mounted on a heat sink on the upper left side of the PCB assembly. The Low B power supply areas consisting of {Q820, Q829, Q835 & Q870} occupy the reminder of the PCB.
The 5V Standby source from the Power Supply Board is used to enable the TV microprocessor and other sections of the signal board, when the unit is OFF. Next is a junction of two protection inputs. Pin-13 of P807 is directly connected to Pin-7 of P808 on the Power Supply. This protect input is from the Power Supply microprocessor and the other is from circuits monitoring the voltages generated on the Low B board.
The Power Supply microprocessor monitors the voltage generated by the Main Power Supply and if they are abnormal the protect line originating at the Power Supply Microprocessor will go High, causing shut down and an error code. {Power :LED Flashes in (0.5) seconds intervals.}
If a voltage generated on the Low B audio board should become excessive, the protect line originating on the board itself will rise, causing shut down and an error code. {Power LED Flashes in 0.5 seconds intervals}.
To effect shut down when one of these lines rise, they are both coupled to the Gate of an SCR [D819] as a protect line. A High on this line causes the SCR to couduct, Pulling the Power On line from the TV microprocessor Low, and placing the unit to latching shut down state.
Contd:
