Sharp LC-37XD1E, Service Manual

Page: 53 / 198

LC-37XD1E/RU
4 – 22
Backlight failure to light up
Do all the fluorescent tubes light up? NO Check the individual fluorescent
tubes for light-up failure. YES Replace any defective fluorescent
tube (s) with new one (s).
YES
Is the power supplied to CN1 and
CN2 on the inverter unit? NO Check the connection between power
unit and inverter unit.
YES
Iis the Fuse (F201, F401, F251 or
F451) fuse in the inverter unit circuit
functioning? NO Replace the blown-out Fuse (F201,
F401, F251 or F451) fuse on the
inverter unit. Turn on the power again.
If the fuse gets blown out again,
check the short-circuited spot. YES Check T201, T403, T251 and T453
and their peripheral circuits as
IC7502B and their peripheral cir-
cuits.
YES
Is the VCC power supplied to the
control IC (U4) on the inverter unit? NO Check the circuit connected with the
VCC terminal on the inverter control
IC (U4).
YES
Has each control signal come to
CN1?
(INV-ON, INV-BRT and PWM-SEL) NO Have INV-ON, INV-BRT and PWM-
SEL signal come to SC1702(PB) in
the MAIN substrate? NO Check pins (89) and (19) of IC1710
(main PWB) .
YES
Is the specified control signal input-
ted at IC (U4) (INV-CTL) on the
inverter unit. NO Check the line between CN1 and IC
(U4).
YES
Are the Q23 ,Q25, Q24 and Q26
transisters at the primary side of
T201 functioning? NO Check the power line of IC (U4), its
peripheral circuits or replace IC (U4).
YES
Is the secondary circuit of T201 func-
tioning. NO Replace T201 or the T*** transformer
for the fluorescent tubes, or check
their peripheral circuits.