LC-42XD1EA (serv.man4). Troubleshooting Table - Sharp TV Service Manual (repair manual). Page 19

LC-42XD1EA/RUA

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Note: The SD signal (576i 480i) alone passes through the FRC circuit. (The HD signal does not go through.)

                         

                        

                       

Does the image appear with the HD sig-
nal, but not with the SD signal?

Does anything unusual (which or black-
ish screen, block noise, for example) 
appear on the screen?      

Does the image look unusual with the 
power switch turned on?    

YES

YES

YES

Is the power supplied to IC3301 (FRC)?
Is there the FRC-IN signal input at pins 
(142) and (13) of IC3301? 
Check the soldering condition. 

Is there the specified RESET-A signal 
input at pin (39) of IC3301 (FRC)? 
(60 ms delay design)     

Check the connection between pin 
(R22) of IC3002 (V-PRO.) and pin 
(142) of IC3301 (FRC) as well as that 
between pin (N20) of IC3302 and pin 
(13) of IC3301    

YES

NO

Replace IC3301 (FRC).

Check “RESET-A” signal pin (34) of 
IC1710 (FPGA).     

                      
Do all the fluorescent tubes light up?

NO

Check the individual fluorescent 
tubes for light-up failure.

YES

Replace any defective fluorescent 
tubes with new ones.

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 F7502) in the 
inverter unit circuit functioning?

NO

Replace the blown-out fuse (F7501 or 
F7502) on the inverter unit. Turn on 
the power again. 
If the fuse gets blown out again, 
check the short-circuited spot.

YES

Check the transformer (T7501-T7511, 
T7601-T7606) and their peripheral cir-
cuits as well 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(LB)? 
(OFL,OSC,STB)

NO

Have the OFL,OSC and STB signal 
come to P1701(LB) in the MAIN sub-
strate? 

NO

 Check pins (19),(17) and (89) 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 
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 T*** trans-
former for the fluorescent tubes, or 
check their peripheral circuits.