SHARP LCD TV LC-3244E-BK: No Backlight

[Ahakim]

TV on by main AC and then by Remote: front LED green. After about 5sec: complete shut down, LED becomes red. All repeats if disconnected and connected again to AC power.
In this TV both SMPS and Inverter are on the same board (Power/Inverter UNIT):
RUNTKA396WJQZ.
I know by (some/humble) experience that fault might be in lamps. My question is: Is there a way to know for sure that that's the case and not a problem in Power/inverter unit, such as a defective HV transformer or inverter IC (BD9883) fault?
NOTE: All three DC voltages are present: 60V, 13V and 9V.
No bulged C's in power unit. If all 10 lamps are completely taken out would the inverter still work and should I find a HV (1700V) in secondaries or NO NO NO ...? I don't want to take the risk of buying/changing all lamps.
Please HELP. Thanks...

[laikm]

Re: SHARP LCD TV LC-3244E-BK: No Backlight

jumper C7558 and see if display is ok. if still shut off, may be some components have over current

[slickrickybobby89]

Re: SHARP LCD TV LC-3244E-BK: No Backlight

You may be able to force the set to power on by unplugging the set from the wall, holding then input and vol - buttons and re plugging into the wall. This has helped me many times with diagnosing sharp tvs. If the set powers on, and the backlight still fails, then you have a backlight issue, either a circuit or bad lamp, if the set powers on and has a backlight but no image, then you have either a bad mainboard or a bad t-con, if the set powers on and appears to be fully funtional, then you may have the issue laikm is referencing, something is over current, tripping the protection circuit.

[laikm]

Re: SHARP LCD TV LC-3244E-BK: No Backlight

Forgot to let you know the detail of board.

It is a IP board of part no RUNTK419WJQZ . I downloaded a similar schematic RUNK396WJQZ from website and use it as referance

Prior to adding jumper to C7558, i replaced the below two mosfet as i suspect this is rootcause of display shut off after few seconds but have sound

Q7502 2SK3599 replace with B31N20D ( TO220AB and use inusalator between heatsink and body)

Q7501 2SJ655 replace with IRFS31N20D ( D2pak , but modified by using bare wire to join SMT lead and an insulator between body and heatsink).

Now these two devices become short circuited after jumping C7558 with wire.

TV show green LED and no display and no sound
The situation become bad and have to trouble shoot where it go wrong

[laikm]

Re: SHARP LCD TV LC-3244E-BK: No Backlight

many works were done before i decided to add jumper at C7558 to force start TV

a) replace high voltage ballatic cap
b) measure resistance of HV inverter transformer and found no significant difference
c) replace C7215,C7216 and C7217 1000uF , 25V at power circuitry

thought to replace DC-AC inverter Controller BD9883FV, but thinking if can use BD9222 as subsitution. I got this device from junk inverter board from Toshiba LCD TV.
No data sheet from website to change pin assignment and Vcc . Ever wrote to ROHM to ask a copy but they refused to provide with the reason of customised device

[laikm]

Re: SHARP LCD TV LC-3244E-BK: No Backlight

hi. i fixed no power up, but with standby5V problem that happened after shorting C7558 as described on 8.17.2016, 9.54pm. Q2115, 2SK4096LS was found faulty and replaced with 2SK3561. Now 60V, 13V from power board is ok, but old problem still happen. Display shut off after several seconds but have sound.

i do not want to try shorting C7558 again .

Any solution for Display shut off after several seconds but have sound.?? Only DMM on my hand and no other equipment for troubleshoot. Need advice

[laikm]

Re: SHARP LCD TV LC-3244E-BK: No Backlight

I used wire to short c7558 and the display is ok now. Found minor black strip horizontal line. I believe that one of ccfl bulb going to be faulty. So probablybad ccfl bulb cause shut down display or protect short circuit scp of bd9883

[dick_barton]

Re: SHARP LCD TV LC-3244E-BK: No Backlight

Or one of the tubes may have become dislodged from its connector and need reseating.

[fredaelsadany]

Re: SHARP LCD TV LC-3244E-BK: No Backlight

HI
this backlight problem as a result of old lamp or broken lamp .
put pin 12 as in pic to ground if backlight is off there is a broken lamp or loosen connection you must open the back light to change the lamp .