Sharp LC-37AD1E Service Manual page 52

LC-37AD1E
The backlight does not go on.
Is any of the fuses of
F7501-F7504,
F7551-F7553,
F7611-F7614 and
F7641-F7643 blown?
YES
Check the inverter
circuit downstream
from the blown fuse.
No sound comes out. (Checking with the AVC
System connected)
Is power supplied to each IC
on the AUDIO PWB?
YES
Is the audio signal applied to
pin (7) (L-IN) and pin (9) (R-
IN) of P3804?
YES
Is the audio signal applied
to pin (13) and pin (15) of
P3803?
YES
Is the output signal from the
1-bit amplifier applied to
P3903?
YES
Check if the internal/external
switching relay (RY3901)
functions correctly.
Is the control signal applied to
No
pin (2) (OFL1) and pin (3)
(OFL2) of P7506 and P7616?
YES
Is power supplied to each
Inverter PWB?
YES
Check the wire connecting the Inverter-1 and -3 PWBs, the
wire connecting the Inverter-2 and -4 PWBs, the board-to-
board between the Inverter-1 and -2, and the board-to-
board between the Inverter-3 and -4.
Check the counterpart
inverter circuit on the
opposite side.
No Check if 5V is supplied to the power
regulator circuit (IC3812 and IC3816)
and pin (2) of P3804.
Is the audio signal applied to
No
pin (13) and pin (20) of
SC2202 on the Monitor PWB?
YES
Perform checking around Q2012 and
Q2014 and check the wire between
Monitor PWB and Audio PWB.
Are the MUTE circuits
No
(Q3804 and Q3805)
operating?
Perform checking around
No
IC2004, IC3804 and the 1-
bit amplifier.
Is the harness connected correctly
No
between the Monitor PWB and
Inverter-1 and -3 PWBs?
YES
Check the peripheral circuitry of
IC4501 of the Monitor PWB and
check the operation of Q7704
and Q7705.
No
Check the 15V output on the
Power PWB.
Check the connection of the high-voltage
(pin (2)) wire on the side of the blown
fuse and check that of the counterpart
high-voltage (pin (2)) wire of the
fluorescent lamp on the opposite side.
No
No
52
Check for the AVC
System side for output.
Perform checking
around IC3803 and
IC3808.