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Thread: Calling TV tech's- is it my Sharp TV 70" powerboard ?

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    Default Calling TV tech's- is it my Sharp TV 70" powerboard ?

    Hi all,our beloved Sharp large screen TV died after 6 years.I say beloved as it has been an awesome performer picture-wise ,not smart but we use a Chromecast.We also use a Beyondwiz PVR as the primary tuner which has a slightly better image than the Sharp tuner incidentally.
    A couple of days had a sudden failure with a total loss of power.No red standby led etc.Dead.Pulled the back off and checked the ceramic fuse for continuity and then power throughput-good.No visible capacitor damage etc.
    The power board is the largest physical board which I'm guessing is pretty common.I've found a couple os one on Ebay the other on the web.One in China,one in HK.Either could be purchased and got here express ( DHL ) in about a week for ~$300.Who knows how long now though in these uncertain times.Given home possible detention we need a TV.
    Appreciate any opinions as to whether I should just take the chance and buy the board ?



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    Thread moved to correct section.

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    No model number ~ tough ask.

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    Sorry model number is LC-70LE650X

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    take a short cut and a new tv

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    Would be nice-haven't the finances unfortunately...

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    Same power board as this?



    -- see the diode bottom right [D7901] ; iirc that's the standby power rectifier diode ; my guess is that's dead/shorted ... if so replace it and set should work again.


    edit: just found this YT vid - different model but at a guess same failure mode
    Last edited by wotnot; 24-03-20 at 09:08 PM.

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    Quote Originally Posted by wotnot View Post
    Same power board as this?



    -- see the diode bottom right [D7901] ; iirc that's the standby power rectifier diode ; my guess is that's dead/shorted ... if so replace it and set should work again.


    edit: just found this YT vid - different model but at a guess same failure mode
    That's exactly my board and I can see that diode,would it be something like a 400v ,3A-something like this ? :
    I don't have the circuit of the board so have no idea of values.
    Thanks a million,appreciated

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    <-- needs to be a high-speed schottky ; check with multimeter first to confirm fault condition

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    Quote Originally Posted by wotnot View Post
    <-- needs to be a high-speed schottky ; check with multimeter first to confirm fault condition
    Thanks again,forgive my ignorance but can the diode be tested for forward and reverse current in situ ?

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    Quote Originally Posted by WouldbeAlarmist View Post
    Thanks again,forgive my ignorance but can the diode be tested for forward and reverse current in situ ?
    Its getting late,I know the answer to that !

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    Quote Originally Posted by WouldbeAlarmist View Post
    Its getting late,I know the answer to that !
    No,no luck.Diode seems fine.....
    Back to the drawing board

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    Bugger....I still like standby power source for this fault (and it's been years since I worked on such sets) but again iirc, that section is ;



    I would now suspect that SMPS controller IC (builtin switching mosfet) - check all diodes & such in that immediate area ; get part# of the IC and view datasheet to get pinouts etc ; apply mains power to board, and see if that IC is actually working ; BIG FAT WARNING -- input to that IC will be at near 400VDC ; do NOT proceed with a powered main AC test unless you fully understand the danger!!

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    Quote Originally Posted by hinekadon View Post
    take a short cut and a new tv
    I just wanted to remark about this statement as very much -not- being 'defeatist' ~ often it's very realistic.
    With this set for instance ~ standard service procedure for this problem, is replace the power PCB ; there's none of that diagnose at component level stuff.

    I also failed to address OP's question of whether or not it made sense to splash out 300bucks on a good used power PCB to get the set working again ~ just imagine it turned out it *was* that diode, and the fix only cost you a few dollars and a bit of soldering. Buying the used part might work, but how long before (if) it suffers the same fault? Older gear is like this, any many of us in (used to be in) the game, know that certain brands/model all suffer from common mode failures...what happens to one will happen to others, it's how it goes.

    A couple of times I've seen fixes/work-arounds for this design of standby power supply, after one finds that SMPS controller IC is toast, and the actual part is no longer available. What you do is supplement the standby power circuit, and provide a 240vac -> whatever voltage you need, and feed that to the standby circuitry after pulling the rectifier diode out of the way to give you an injection point & uncouple things from the non functioning section.

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    if you pull the diode and stuff i couple of aa cells int to it you may find that it will turn on but Im getting OLD so i dont know weather that trick is appropriate any more they have just about to go into lockdown in nz and I get a phone call telling me to pick up my essential services permit and Im over seventy . I think they are trying to kill me ????? I dont have to do any work they gave me a gofor as well , Thats life eh ?

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    Shit bro'. starting to suck & bite at the moment huh... ;( Yeah, that sort of trick can work as well ; for most folks though just finding someone to fix things like this (without charging an arm&leg) is the tough part.

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    Quote Originally Posted by wotnot View Post
    Bugger....I still like standby power source for this fault (and it's been years since I worked on such sets) but again iirc, that section is ;



    I would now suspect that SMPS controller IC (builtin switching mosfet) - check all diodes & such in that immediate area ; get part# of the IC and view datasheet to get pinouts etc ; apply mains power to board, and see if that IC is actually working ; BIG FAT WARNING -- input to that IC will be at near 400VDC ; do NOT proceed with a powered main AC test unless you fully understand the danger!!
    Yep Bugger... haha,some ppl have much more bugger than this-I just want to watch telly !
    I checked the former diode with my old faithful Fluke 73 with diode function.So I can test the others you mention as well.
    I'll follow your suggestions re the IC when I have a chance.I've had a look and identified it.
    The guy in China is unrelentless in what he is asking for the powerboard-he only thinks in $US !
    Appreciated again,cheers
    PS BIG FAT WARNING TAKEN HEED OF !!! I don't need in more shocks at this stage of my life

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    What is the device number on the Standby Supply SMPS I.C.?
    A datasheet should not be too hard to find. See if it needs a start resistor. one of the resistors in proximity to the I.C. looks somewhat distressed.
    BTW, I have this exact model TV and it's been a great performer thus far.
    "The saddest aspect of life right now is that science gathers knowledge faster than society gathers wisdom." - Issac Asimov

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    Quote Originally Posted by TVguy View Post
    What is the device number on the Standby Supply SMPS I.C.?
    A datasheet should not be too hard to find. See if it needs a start resistor. one of the resistors in proximity to the I.C. looks somewhat distressed.
    BTW, I have this exact model TV and it's been a great performer thus far.
    I'll look in the morning for the device # .Incidentally that's not my board.That was posted by OP
    But yes,great TV

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    Quote Originally Posted by WouldbeAlarmist View Post
    I'll look in the morning for the device # .Incidentally that's not my board.That was posted by OP
    But yes,great TV
    Yeah, 'for illustrative purposes/reference only' ...<grin>... BTW, do feel free to post an image of -your- power PCB, sometimes a something can stand out ; good idea to take pictures of both top and bottom side (if you remove board from chassis, which is gunna have to happen anyhow =)

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