LC-37XD1E (serv.man4). Troubleshooting Table - Sharp TV Service Manual (repair manual). Page 22

     LC-37XD1E/RU

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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 CN7501 on 
the inverter unit?   

NO

Check the connection between power 
unit and inverter unit.      

YES

Is the Fuse (F7501 or F7701) fuse in 
the inverter unit circuit functioning?

NO

Replace the blown-out Fuse (F7501 
or F7701) fuse on the inverter unit. 
Turn on the power again. 
If the fuse gets blown out again, 
check the short-circuited spot.     

YES

Check T7501 and T7701 and their 
peripheral circuits as IC7501 and 
their peripheral circuits.    

YES

Is the VCC power supplied to the 
control IC (IC7501) on the inverter 
unit?   

NO

Check the circuit connected with the 
VCC terminal on the inverter control 
IC (IC7501).     

YES

Has each control signal come to 
CN7502? 
(INV-ON, INV-BRT and PWM-SEL)  

NO

Have INV-ON, INV-BRT and PWM-
SEL signal come to P1701(LB) in the 
MAIN substrate?    

NO

 Check pins (89) and (19) of IC1710 
(main PWB) .

YES

Is the specified control signal input-
ted at IC7501 (INV-CTL) on the 
inverter unit. 

NO

Check the line between CN7502 and 
IC (IC7501).     

 

YES

Are the Q7501 and Q7502 transis-
ters at the primary side of T7501 
functioning? 

NO

Check the power line of IC7501, its 
peripheral circuits or replace IC7501.     

 

YES

Is the secondary circuit of T7501 
functioning.  

NO

Replace T7501 or the T75*** trans-
former for the fluorescent tubes, or 
check their peripheral circuits.