Sony KDP-57XBR2 Training Manual page 95

Chapter 23 - RA-6 Protect Circuit Troubleshooting
General Description
As illustrated in Figure 23-1, several circuits are monitored for protection. Some lines are monitored by the self-
diagnostics feature while others are not. The self-diagnostics feature can assist in isolating a particular circuit.
Below is an example of the diagnostics page which is entered by pressing "DISPLAY", "5", "VOL –", and "POWER":
Self Check:
2: +B OCP
3: +B OVP
4: V Stop
5: AKB
6: Low B
7. H STOP
8. HV
9. AUDIO
101: WDT
The numbers on the left indicate how many times the timer LED flashed, which designates the probable cause of
the shutdown. The flashes on the LED will occur at one second intervals, followed by a three second separation
period and repeat again. The numbers at the extreme right indicate how many times the problem occurred up to
99 events. You can see why this is beneficial for intermittent troubleshooting. It is always a good idea to clear the
events before exiting and that can be done by pressing "8" "enter" on the remote. This is not the same as
pressing these buttons in the service mode. It will only clear the events and not reset customer defaults. Beware
that the service manual instructs you to enter the service mode to clear these and that is a mistake. You can do
it right from this screen.
+B OCP: Excessive current on the 135V line. This is usually caused by flyback problems or secondary loads on
the line. The circuit could also be tripping for no reason. This is why you should always monitor AC current while
the unit is shutting down. It will help to know if you are really dealing with an over-current condition and a more
cautious approach can be taken while troubleshooting.
+B OVP: The 135V line has exceeded 139 volts. Refer to Chapter 22 on troubleshooting regulator problems.
V Stop: The vertical deflection circuit has stopped operating. Loads on the I
the source of this problem.
AKB: One or more CRT cathodes are unable to generate sufficient current to return a good feedback pulse. The
AKB detect circuit may also have failed. It is common to see multiple events in this diagnostic feature along with
registered HV failures. See the special section in Chapter 27 on AKB at the end of this manual.
Low B: The 5V source from the main power supply is monitored for low voltage by Q714 on the A board.
Problems on the +/- 15V, +/- 19V and the +/- 22V lines can also generate a diagnostic indication here.
H Stop: Horizontal deflection has failed. Since the unit has a separate high voltage circuit, the set will shut down
to protect the CRTs. This will be covered in Chapter 23.
HV: High voltage has exceeded specified limits or there is excessive current in the flyback transformer.
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23. RA-6 Protect Circuit Troubleshooting
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C data and clock bus can also be