Power Supply Block; Troubleshooting - Sony KV-32FV16 Training Manual

Power Supply Block

Overview
The power supply in the AA2U chassis is located on the G board. It is
nearly identical to the power supply in the AA2W chassis. AC from the
outlet is applied to a series of line filters and protection devices and is
eventually applied to the standby supply, AC rectifier and degauss cir-
cuits. The Standby supply is a switching supply whose output is applied
to a 5-volt regulator. The output from the regulator exits the G board at
CN641/10. It is applied to various components in the set that need to be
powered when the set is OFF. These include the Micon, remote sensor
and S Link circuitry if applicable.
When the set is turned ON using the power button, remote control or S
Link, 5 volts is applied to CN641/11. This 5 volts is used to turn RY600
Power Relay ON. When the relay closes, a click is heard. Closing the
relay allows the AC voltage to be rectified and applied to the converter
circuit. The converter begins operation when this voltage is applied. The
power ON line is also applied to the soft start circuit. The soft start circuit
holds the B+ voltage low while the power supply capacitors charge by
controlling the voltage present across the control winding. The control
winding determines the switching frequency of the converter. After soft
start operation is complete, the regulation circuit takes over operation of
the control winding. The regulation circuit produces an error voltage by
monitoring the +135 volt line. This allows the converter's output to be
coupled through T605 to the secondary supplies. These secondary sup-
plies power the rest of the set.
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Shortly after the click of the power relay at turn ON, another click is heard.
This click is RY601 Degauss Relay closing. This may be accompanied by
a hum sound that indicates the operation of the degaussing coils. There
is a third click that occurs about 8-10 seconds after the unit is turned ON.
During operation of the set the +135 volt line is monitored for DC protec-
tion. This protection circuit is used in conjunction with the latch to switch
the Power ON line LOW if a failure should occur. This will turn RY600
Power Relay OFF and turn the power supply OFF. In addition, a foldback
circuit can also shut down the power supply. The foldback circuit com-
pares the secondary's +12 volt output to a voltage on the primary side. If
there is a problem with either one of these circuits, the set will be forced
into soft start mode. This will cause the set to shut down.

Troubleshooting

Use this drawing to quickly check voltages on the G board connectors.
These connectors can be accessed by pulling the three boards at the
bottom of the chassis towards the rear about 3 or 4 inches.
CN641
pin 1
CN642
pin 1