Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: Contrast John on April 24, 2010,10:38:22
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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.
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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
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Hi sparky
Thanks for the reply. Have tried that but no joy. Guess it`s going to be a tricky one!
Regards
John.
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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.
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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 .
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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.
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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
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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.
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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.
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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
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hi just had one repaired under warranty guy came changed backlight tubes ,cured fault similar symptoms to yours
original tubes had black ends
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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.
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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
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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
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please can you show me the position of the smd fuse cause i cant find it. sorry to be a pest.
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Hi
I will try to find out for you
Brian
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Hi
I have posted a pic, I hope it worked
Brian
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found the fault boys.the smd fuse gone.what causes it to go ane the value please.
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replaced smd fuse but blew.
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Hi Chrissie
Any joy with your set? Not had any problems with fuse blowing on this model. Would be interested to know the cause.
Regards
John.
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shall let you all know when i find out the prob!!. :dubbio:
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Hi Chrissie,
I got your message, and ive sent you the circuit diagrams
Brian
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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.
I am tring to short out the ic on this tv but I cannot for the life of me find the C7558 smd capacitor to short.
if you have got a picvture or ou could describe where the cap is located it would be greatly appreiciated.
I have looked at the picture in the thread annd that confused me even more because the capacitor is not at that location.
if anyone has the circuit diagram please could you mail it to me
thanks bm
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Hi bm
c7558 is located about an inch away from the BD9883 driver IC. Both are surface mounted components. Circuit diagram for the inverter is not included in the manual-seems to be the way these days. Service manual is available to download free here-
http://elektrotanya.com/
Regards
John.
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Very usefull bit of info regarding shorting out C7558 john. Have one in for repair whith same fault and now after shorting out C7588 i am able to see a slightly dark area across the screen approx a quarter of the way down from the top. Just wondering now if this will be as a result ot two tubes or just one being faulty. I think you said that you changed them as a pair,where they both faulty?
Phil
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Hi Phil
Yes two were faulty on that one but it seems more common that just one is u/s. Check to see if your dark band is narrower at one side than at the other. If it narrows to a couple of inches it's probably just one tube.
Have found it useful to mark the position of the faulty tube before dismantling fully, so as not to swop the wrong one.
Regards
John.
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Hi john and all,just to let you know i have sorted the tv. The third tube down from the top was faulty,got one from charles hyde & son,next day delivery. I have been wary of dismantling lcd screens to change lamps as idealy clean room conditions are required. Under no circumstances should the polariser be layed down when taken out as it will collect dust and hairs. The best thing to do is to flip it in to the inside of the screen when it is lifted off, and then stand the whole thing verticaly leaning against a wall ect.
Phil
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Hi Phil
Nice result and thanks for the tip. Will use that next time. Nothing worse than completely rebuilding the set only to see a hair illuminated behind the screen!
Regards
John.
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Thank for all the help lads I have now got this set up and working fine :sign0098:
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:c017: I tried shorting out C7558 and applied the service menu routine and i too can see a dark area in the centre of the screen with words stating 1,2,3,4,5 Lamp Error ooh oom Approximately. I too must have a Tube that is defective. Thank you for this
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Hi chaps...
I have been reading up & working on one of the above TV's. Sharp 32D44E.
I've read through all the threads about this set being stuck in Standby and have tried the service mode, Protection circuit bypass ect ect... I can get the TV to come on with green light as I try to enter the service mode yet I still get no backlight and ultimately nothing on the screen.
I have looked closely at the various diagrams & Service manuals scattered about the place which helped to find what I suspect to be my problem.
On the reverse of the inverter board I have found a couple of burned out SMT diodes around the inverter switching FET's. Q7501 (On heat sink) has gone S/C taking with it D7522 and D7525 on the reverse of the board. Now, I'm pretty sure these are the only components in the area which are dead.
My problem is that I cannot identify the components due to the fact that they are blown to bits and there is not even a reference to D7525 on the circuit Diagram I found in this thread... http://www.tv.quuq.org/forum/index.php?topic=5186.0 (http://www.tv.quuq.org/forum/index.php?topic=5186.0)
Can anybody help to locate replacement diodes please? Also, not having reference for D7525 on the diagram I need to know the orientation of this please.
Thanks.
Paul.