Troubleshooting - Casio QT-7300 Service Manual

7. TROUBLESHOOTING

This portion of the service manual lists all possible malfunctions that may occur when operating the QT-7300
system. To assist you in fully analyzing the problem, the following table also includes an up-to-date list of
symptoms and probable cause(s). In case you encounter problems or discover causes not included in this
section, we highly recommend you to consult CASIO engineers.
Symptoms
The power LED
indicator on the front
panel does not light
up.
Abnormal VGA screen
display
Abnormal LCD screen
display
COM Port is not
functioning
– Loose power cable connection at the bottom of the front panel
Turn OFF system power then disconnect the power cord. Insert the
power cord back into the inlet connector then turn ON the system power.
– The connection of female jacks to the power supply inlet connector is
loose.
Remove the back cover of the system and check each connection to the
power supply inlet connector.
– Loose connection on the bronze and blue copper wires of the power switch
Check each connection.
– Power supply unit is out-of-order,
Replace the power supply unit.
– Monitor cable is not properly installed to connector VGA of the system.
– Loose connection between the multi-I/O (VGA) expansion card and the
CPU card.
Pull out the multi-I/O expansion card from the CPU card then re-install
it back. If symptoms persist, replace the multi-I/O expansion card.
– Defective CPU card
Replace the CPU card of the System.
– The brightness control is not properly adjusted.
Adjust the brightness control to a satisfactory level.
– Inverted connection (from LCD converter board to CPU card) of the 44-pin
LCD converter cable
Adjust and install the LCD converter cable properly.
– Loose connection between the LCD converter board and the LCD panel
Pull out the LCD converter board from the LCD panel then re-install it
back.
If symptoms still persist at this stage, replace the LCD converter board
and/or the LCD converter cable
– Defective LCD panel and/or inverter
Replace the LCD panel and/or inverter.
– Defective CPU card
Replace the CPU card of the system.
– Incorrect BIOS version
Upgrade the BIOS version. Consult CASIO engineers for the latest
version.
– Loose connection between the multi-I/O (COMx) expansion card and the
CPU card.
Pull out the multi-I/O expansion card from the CPU card then re-install it
back. If symptoms persist, replace the multi-I/O expansion card.
– Defective CPU card
Replace the CPU card of the System.
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Probable Causes