Self Diagnostic Circuit - Sony KV-32XBR400 Training Manual

Self Diagnostic Circuit

When the TV shuts down and the standby LED blinks, the Main uCom
IC701 knows which failure activated the shutdown. The number of times
the Standby LED blinks indicates the problem board or section.
Shutdown - Standby light does not blink
Circuit - The current on the +200 volt line is monitored by R8043 and
Q8009. This 200-volt line supplies the High Voltage Converter stage,
which feeds the flyback. A short in the flyback or excessive high voltage
will demand sufficient current to shut down the TV. Since there is no
connection to the Main uCom IC701, the standby LED will not indicate
this failure.
Unstable standby voltage or a defect in the basic latch circuit (Q6530 and
Q6532) will also cause the TV to shut down without the standby light
blinking. This last problem is rare.
Testing - To determine if the +200V line to the HV Converter stage is
causing shutdown, monitor the voltage at Q8009/Collector at power ON.
The voltage should not rise above 0.2Vdc at power ON. A higher voltage
means the problem is on the D board in the Converter.
Shutdown - Standby light blinks two times
There are two +135V OCP monitoring circuits. The first circuit will cause
the Standby light to blink two times and the second will cause the light to
blink seven times. Both sensing and output circuits are on the D board
but the indicating circuit is on the A board.
Circuit - R6598, R6591, Q6520, Q6521, and Q6524 monitor the current
on the +135V line from the Secondary Power Supply. The +135 volt line
supplies:
♦ Velocity modulation (V) board
♦ Horiz Output (Q5030) and PWM (Q5003) stage (D board)
♦ The HOT supplies +200V to the RGB Output ICs (C board).
Testing - The blinking LED indicates the failure, but the problem could be
in one of three locations: The H. Output/PWM stage, the sensing circuit
on the D board, or the sensing circuit on this A board. Verify this problem
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by monitoring CN6506/pin 8 as you power ON. If the voltage does not
rise above 0v at power ON, the problem is not on the +135V line. If the
voltage reaches 1.2V, disconnect the V board and try again. If the CN6506/
pin 8 voltage still rises to 1.2V, test the H Output and PWM transistors or
replace the entire D board.
Shutdown - Standby light blinks three times
Circuit - There are two possible causes for this LED indication caused by
excessive voltage. Two power supply voltages are monitored, +135V on
the D board and Unreg. 7V on the A board. On the D board, the maxi-
mum voltage on the +135V line is +140V. This is monitored by IC6505
and Q6522. On the A board, the maximum voltage on the unregulated 7V
line is 8.2V. This is monitored by D6014.
Testing - The problem can be on either the A or the D board. Locate
D6017/Cathode or D6014/Anode and monitor this voltage as you power
the TV. If the voltage rises above 1V, the problem is in the A board's
power supply (regulation). To test the power supply on the D board, monitor
CN6506/pin 7. If this voltage rises above 0.6Vdc, the problem is on the D
board.
Shutdown - Standby light blinks four times
Circuit - A vertical failure because of the output IC or power supply (both
on the D board) will cause the Y/C, CRT Drive IC201 to send emergency
data to Main uCom IC701. IC701 turns the TV by opening the AC relay
(IC701/pin 69 goes LOW).
Testing - Measure the +15v and -15V to the vertical output IC5004/pins 2
and 4 before you suspect the IC5004 itself.
Blanking - Standby light blinks five times
Circuit - The Ik signals are measured by Y/C, CRT Drive IC201 and are
used to adjust the RGB gain to maintain color balance. As the picture
tube ages, the Ik signals may fall below the threshold for automatic bal-
ance and mute/blank the picture.
Testing - Increase the G2 control on the CRT's C board. If that does not
return cathode current to within operating range so the picture will ap-
pear, examine each filament to see if it is lit.