Sony KDP-57XBR2 Training Manual page 94

3. If a problem exists that warrants protection, a third relay click will be heard. This is actually RY6002 and
RY6003 releasing simultaneously and will occur from one to several seconds later. Refer to Chapter 23
for troubleshooting the protect circuits.
Assuming two rapid clicks are not occurring and little or no AC current is being drawn, the main supply must now
be checked. Place a jumper across RY6002. This will provide start and sense voltages to IC6003. Unplug the
C boards from the tubes while performing this. Verify 340VDC at Q6006-D. If it is missing, R6064 has opened
or the unregulated B+ line is faulty. If unregulated B+ is present, check pin 18 of IC6003 for start voltage. At
120VAC input, the normal voltage at this pin is approximately 340VDC. Check for 2.8VDC at V Sense pin 1.
Verify zero volts at OCP pin 9. If any DC is read, R6086 and R6080 have opened. The oscillator inside IC6003
will run if both voltages are correct and OCP is zero. Check for drive pulses at pins 12 and 16 of IC6003. If none
are present, IC6003 is probably defective. If they are present at the output pins but not at the FET gates, one or
more of the protection diodes are leaking or shorted. The gates of Q6005 and Q6006 may be shorted but this is
rare.
B+ Regulation Problems: The regulation loop is relatively easy to troubleshoot. IC501 monitors the 135V line via
R5032. Any rise in the voltage at pin 1 of IC501 will cause the output at pin 4 to go lower. The resulting pull-down
at PH6001 pin 2 causes the LED to increase in brightness. Pin 4 of PH6001 will pull down the voltage at pin 2
(FB) of IC6003 and the oscillator frequency will rise to reduce the output voltages at the secondary lines. The
opposite chain of events will occur if the 135V line should drop in voltage. The use of variable DC voltages in the
regulation loop allows for simple troubleshooting methods.
Excessive B+: The unit will shut down and the timer LED will blink in sequences of three. The ideal
method of troubleshooting is to isolate entire sections of a circuit at one time. Monitor the 135V line with
a DVM while testing this circuit to verify a legitimate regulation problem. If the 135V line is not going
above 139V, the OVP circuit is malfunctioning. This will be covered in Chapter 23. By shorting pin 4 of
IC501 to ground, the result on a normally functioning supply would be a significant drop in secondary
voltages. If the unit still goes into protect with pin 4 of IC501 shorted, the failure has been isolated to
PH6001 and its associated components or even IC6003 itself. If the unit stops going into protect, the
failure lies between IC501 and the sample taken from the 135V line. IC501 is known to be extremely
reliable and an increase in value of R5032 is likely.
Low B+: Read the voltage across PH6001 pins 1 and 2. Zero volts present indicates IC501 is reacting to
the low B+ correctly and turning off the LED. Measure the DC voltage at pin 2 of IC6003. If it is lower than
2VDC, PH6001 is the cause. If more than 2V is present, check pin 6 of IC6003. The capacitor to ground
(C6021) controls the soft start duration at turn-on by charging. If C6021 shorts or has leakage, the
oscillator will remain in high frequency and generate low output voltages.
22. RA-6 Power Supply Troubleshooting
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