LC-52XD1E (serv.man5). Trouble Shooting Table - Sharp TV Service Manual (repair manual). Page 23

LC-46/52XD1E-RU

6 – 23

46INV         

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).

Is the power supplied to CN7401 and 
CN7601 on the inverter unit?   

NO

Check the connection between power 
unit and inverter unit.      

YES

Iis the F7401 and F7601 fuse in the 
inverter unit circuit functioning?

NO

Replace the blown-out F7401 or 
F7601 fuse on the inverter unit. Turn 
on the power again. 
If the fuse gets blown out again, 
check the short-circuited spot.     

YES

Check T7401 and T7601 and their 
peripheral circuits as IC7401 and 
their peripheral circuits.    

YES

Is the VCC power supplied to the 
control IC (IC7401) on the inverter 
unit?   

NO

Check the circuit connected with the 
VCC terminal on the inverter control 
IC (IC7401).     

YES

Has each control signal come to 
CN7402B? 
(INV-OFL,INV-OSC,INV-STB,INV-
BRT)  

NO

Have INV-OFL/OSC and the INV-
STB signal come to P1701(LB) in the 
MAIN substrate?    

NO

 Check pins (19),(17) and (89) of 
IC1710 (main PWB) .

YES

Is the specified control signal input-
ted at IC7401 (INV-CTL) on the 
inverter unit. 

NO

Check the line between CN7402 and 
IC7401.     

 

YES

Are the Q7403 and Q7404 transis-
ters at the primary side of T7401 
functioning? 

NO

Check the power line of IC7401, its 
peripheral circuits or replace IC7401.     

 

YES

Is the secondary circuit of T7401 
functioning.  

NO

Replace T7401 or the T74** trans-
former for the fluorescent tubes, or 
check their peripheral circuits.