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Trouble
shooting for usual failures:
Unable to burn and record
The 12V power
provided to the AD board by the power supply board is normal, and the
connection of the VGA signal wire is good, but the program cannot be burnt and
recorded. Check as the following steps:
* Firstly check whether the power supply system
on the main board is normal or not. Whether the U4 output is 3.3V?
* After the power supply is normal, firstly
measure whether the crystal vibrator X2 starts to vibrate or not, and use the
oscillograph to measure whether Y2 exports the pulse wave? (If no oscillograph,
use the multimeter to measure the voltage on both sides of Y1)
* After the vibrator normally works, check
whether there are signals being transmitted on Pins 1, 2, 5 and 6 on U8 (PM25LV512)
White screen
Firstly we
should know what the white screen is? Why there will be a white screen? The
phenomenon of the white screen is that the panel emits the white light, but has
no any picture. The reason is the crystal screen does not work normally: The back-light source (Tube) of the screen is working normally, but the crystal screen does not work. Although the screen emits light, that is just that the
tube is on.
* Check whether the 3.3V power supply around
the main IC is normal or not.
* Measure whether X1 starts vibrating? (If the
button switch is ok, this check can be omitted)
* Measure the
input and the output on the U4 of the MOS tube that supplies power to the
screen. In most cases, the reason of the
white screen is the abnormal power supply for the screen, so after finding out
where cannot supply power to the screen, you can easily solve the problem of
the white screen.
Disorderly
screen
Disorderly
screen is that the control buttons for OSD are all OK, and the screen is on, but the picture is abnormal, having the phenomena of coarse pictures, grains
and disorderly picture, etc. Due to the
OSD controls are OK, it means the main IC works normally, the key point should
be on the input & output sides of the signals.
* Start up the
aging signals, to check whether the black, white, R, G and B outputs are OK or
not, to find out whether there is a problem in the front input or the back input, and then check whether the input or output circuit has the short circuit
or the bad component accordingly.
* If there is no problem in the fore said
positions, the main chip can be replaced.
No signal
It works
normally when using the aging signals, but when inserting the signals, it
display No Signal (No signal input). The normal work of the aging signals means
the MCU is working normally, and the signal output circuit is normal. At this
moment, it only needs to check whether the signal input circuit is OK or not,
and at last, consider replacing the main chip.
Black screen
Black screen
here means the crystal screen is not on at all, but the button board can
control switches. In most cases, the reason of the black screen is that the
tube does not work, so the focus should be to check whether there is voltage on
On/Off that controls the work of the inverter on the power supply board.
* Firstly, press the power button to start,
measure whether it is in the high voltage level (3.3V) of the inverter on Pin 3
of CON3? If not, check whether the input & output voltage on Q2 is normal
or not, and whether the PANEL_LIGHT/ON output extending to the main IC is in
the low voltage level (0V) or not?
* If the voltage on the PANEL_LIGHT/ON is
normal, then you can determine the inverter on the power supply board has the
problem.
Color
deflection
The picture
display is normal, but the color is not pure, deflecting to red, green and
blue. For color deflection, it is important to determine whether it is caused
by input or output.
* Firstly, make judgment. Start up the aging
signals, and observe whether the outputs of black, white, R, G and B are OK or
not, and if the color is normal, it means there is no problem on the signal
output circuit, and the input circuit of the front signal is broken, otherwise,
it means the input circuit for the back signals has the problem.
For the input circuit of the front signal,
check whether it has the problems of short circuit or holiday in focus, and
then check whether the resistance values of various components are correct or
not.
For the output circuit of the back signals,
it only needs to check whether it has the problems of short circuit or the
holiday and whether the circuit is open.
DDC cannot be burnt and recorded
DDC is saved
in PM25L512, which is burnt and recorded into the MCU through two pins of DAT_DDC_VGA
and CLK_DDC_VGA on the VGA signal wire, and then saved in U8, so it only needs
to check whether the power supply to U8 and the communication between the main
IC and the U8 are OK or not, and at last, you can consider replacing the U8.
Sound source
inspection
When there is
no sound, firstly check whether the power supply is normal or not, AUDIO_MUT
(Whether the mute signal is normal or not) and whether there are signal inputs
in the sound-source input part, and finally, check the signal output part.
After all are normal, and then confirm IC
NC
If it cannot be adjusted, check whether the
VOL signals are normal or not.