Sharp LC32D44 lcd tv

[Contrast John]

Hi All
This set has been playing up intermittently for a few weeks. Sometimes it would revert to standby when the backlight fired up at switch on, or occasionally the backlight brightness would flutter for a minute or so after switch on after which the set would work ok. Now however it just reverts to standby. Have tried starting in service mode but the backlight cuts out after a couple of seconds so no time to check the lamp error counter. Obviously an inverter problem. Have noticed though that CHS stock the ccfl tubes for this model and wondered if they are suspect on this chassis. Would appreciate any input on faults encountered on these models as the cost of the combined psu/inverter is rather a lot to risk.
Cheers
John.

[sparky]

hi
have had a couple sim fault the earth screws on inverter loose ,what
i did clean around screw holes then fitted washers cured fault
sparky

[Contrast John]

Hi sparky
Thanks for the reply. Have tried that but no joy. Guess it`s going to be a tricky one!
Regards
John.

[Turnip]

Hi John,

Note that earthing on the invertor board with Sharp has been mentioned more than once. Have only had dries on drive chips - resolder everything brown'ish - just a thought - Chris.

On re-reading understand it's combined P/S - Invertor, but might just be the same if it's Sharp.

[mem]

Hi John,
Check the power factor correction circuit on the power suppy , although all the output voltages will be correct,but is lacking in current to driver the inverter. You will find that one of the smd resister has change in value. Hope that helps .

[Contrast John]

Hi Chris and mem
Thanks for the input. Condition of solder on the board looks pretty well immaculate. Set is only a couple of years old and hasn`t had that much use. Power FETs attached to a decent heatsink appear to be used to drive the transformers on this model. The possible changed value resistor in the power factor correction circuit is definately needs investigation, but without a psu circuit progress will be slow. Noted quite a few high value resistors in what I presume to be the power factor correction circuit so guess they may well be suspect. Would really appreciate some circuit reference numbers though before I start lifting smd`s.
Regards and thanks
John.

[WILLYAM1]

hi contrast jhon.
hade a same problem in 32'' sharp sorry dont remember the model.
for revert to stby.
maKE RESET YOU can find it in the list in this webesite.
check 2 high vopltage diode and chnge elec capi in primery p/s.
willyam1

[mem]

hi john,
could you tell me the all ic numbers on the primary side of the power supply with the circuit ref no so i can work out the pcf section for you.

[Contrast John]

Hi mem and WILLYAM1
Thanks for your assistance.
Seems to be only 2 ICs within the primary boundary marked on the pcb. They are IC 7101 ( TNY276PN ), and IC7102 (5500A 1D07D13). Board type is RUNTKA396WJQZ.
Regards
John.

[brainstorm]

Hi John,

There is a common problem flagged by Sharp. R8408 smd 0.33ohm (part no VRS-TW2PR33JY)
that can develop a 'crack' or go high resistance. that normally causes no back light with the green led lit.

I will send you a couple of bulletins regarding Lamp contact problems as well

Brian

[astracat]

hi just had one repaired under warranty guy came changed backlight tubes ,cured fault similar symptoms to yours
original tubes had black ends

[Contrast John]

Hi All
Managed to sort this one out. The lamp error counter had reached 5 which means the set needed to be started in service mode (hold down input and vol - on tv set whilst applying mains until the letter K appears on the screen, after which press vol - and prog - on tv set to get the service menu). Had no joy doing this though because the ccfl driver IC (BD9883 smd) was going into protection mode and preventing the backlight from operating. To get round this problem I overode the protection by fitting a shorting link across C7558 (smd capacitor) located near the IC. The set would now start in service mode.
Found that there are some test patterns available in the service mode one of which is a grey screen. Selecting this option showed the problem. The area across the centre of the screen was darker than the rest indicating the centre pair of ccfl tubes weren`t working. This chassis uses 10 tubes driven by 5 inverter transformers mounted in line with them, so before embarking on a tedious stripdown I ruled out the possibility of a duff transformer by swopping the centre one with one of the others. No change of course, so I dismantled the unit and checked the tubes and their holders for any visible problems. None were apparent but replacing the tubes cured the problem. Just needed to clear the lamp error and remove the link
Hope this info might be useful and thanks to the above contributors for the input.
Regards
John.

[sinclairtv]

Hi John,

There is a common problem flagged by Sharp. R8408 smd 0.33ohm (part no VRS-TW2PR33JY)
that can develop a 'crack' or go high resistance. that normally causes no back light with the green led lit.

I will send you a couple of bulletins regarding Lamp contact problems as well

Brian
Can you tell me where this resistor is. Cant find anything starting with '8'. Thanks

[brainstorm]

Hi

I have emailed you the bulletin showing the position of the resistor,

It might be worth having a word with John, because he had quite an in depth investigation into the fault which I think resulted in a faullty backlight tube

Hope this helps

Brian

[chrissie jones]

please can you show me the position of the smd fuse cause i cant find it. sorry to be a pest.