Read Sharp LC-42SD1E (serv.man4) Service Manual online
LC-42SD1E/RU
4 – 24
Backlight failure to light up
Do all the fluorescent tubes light up?
NO
Check the individual fluorescent
tubes for light-up failure
tubes for light-up failure
YES
Replace any defective fluorescent
tubes with new ones.
tubes with new ones.
YES
Is the power supplied to the inverter
unit? (24V) (CN101)
unit? (24V) (CN101)
NO
Check the connection between
power unit and inverter unit.
power unit and inverter unit.
YES
Is the fuse in the inverter unit circuit
functioning? (F1, F2, F6)
functioning? (F1, F2, F6)
NO
Replace the blown-out fuse on the
inverter unit.
Turn on the power again.
If the fuse gets blown out again,
check the short-circuited.
inverter unit.
Turn on the power again.
If the fuse gets blown out again,
check the short-circuited.
YES
Check drive trans and their peripheral
circuits as well as drive FET and their
peripheral circuits.
circuits as well as drive FET and their
peripheral circuits.
YES
Is the VCC power supplied to the
inverter control IC on the inverter
unit?
inverter control IC on the inverter
unit?
NO
Check the circuit connected with the
VCC terminal on the inverter control
IC.
VCC terminal on the inverter control
IC.
YES
Are there control signals (INV-ON,
INV-BRT, PWM-SEL) at LA (CN101)
on the
inverter unit?
INV-BRT, PWM-SEL) at LA (CN101)
on the
inverter unit?
NO
Are there the INV-ON and INV-BRT
signals at LA and LB on the power
unit, and the (INV-ON and INV-BRT)
signals at SC1702 on the main PWB?
signals at LA and LB on the power
unit, and the (INV-ON and INV-BRT)
signals at SC1702 on the main PWB?
NO
Check pins (5) and (7) of IC1710
(main PWB).
(main PWB).
YES
Is the specified control signal inputted
at INV-CTL-IC (U201) on the inverter
unit?
at INV-CTL-IC (U201) on the inverter
unit?
NO
Check the line between LA (CN101)
and INV-CTL-IC (U201).
and INV-CTL-IC (U201).
YES
Are the DRIVE-FET at the primary
side of DRIVE-TRANS functioning?
(U101/U102)
side of DRIVE-TRANS functioning?
(U101/U102)
NO
Replace INV-CTL-IC (U201) or check
its peripheral circuits.
its peripheral circuits.
YES
Is the secondary circuit of DRIVE-
TRANS functioning?
(T1/T2/
TRANS functioning?
(T1/T2/
••• T10)
NO
Replace the DRIVE-TRANS for
the fluorescent tubes, or check their
peripheral circuits.
the fluorescent tubes, or check their
peripheral circuits.
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