Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: Turnip on February 12, 2016,11:11:49
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Hi folks,
Got one in where the screen flashes on and off for several seconds then set cuts to S/by with Red Led flashing once every three seconds.
Have a horrible suspicion that it's another duff Led backlight issue, but surprised it doesn't cut straight away - Any thoughts - Thanks - Chris.
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Hi Chris,
Code 1 is indeed a backlight SOS. Just curious if it uses a TNP4G549 LED drive board. Have a bulletin if it does.
Bruce
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Hi Bruce and thanks,
Does indeed use TNP4G549 board - Chris.
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Hi Chris,
Well then, see if this is useful.
Bruce
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Hi Bruce and thanks,
Had a shufti and the pair of Fets seem OK - Note they're GK1FD328s (Can't find specs on 'em)
Thinking of trying isolate the Led strings to check individually and wonder if anyone has a service manual as can't find a freebie locally.
Noticed that a chap on line had a similar problem where repair folks wanted to charge £100 more than the set cost for a screen replacement - Chris.
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Hi Chris,
Can do you the 50" colonial version.
Bruce
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Hi Bruce, and thanks a bunch,
Seems there are just two strings of Leds - Should make checking 'em easy, winding up slowly with a current limited power supply - See which string is duff. Later checked voltages on strings from caps C9816 and C9818 and found 180v on first and 85v on second cap so guess an O/C string.
Checked screen spec - Strings are 30 & 20 Leds, voltages around 127v & 83v at 285m/a max
Mending might be a different matter though - Thanks again - Chris.
Gather from 'Words to the Wise' that this LG screen has issues, where replacing a Led one day will lead to changing a few more tomorrow - Fun though.
Later - Took it apart to find 5 Leds S/C and another one O/C due to a burn on the strip. Also noted that the strips look pretty well the same as some recently sorted in a Toshiba (Vestel screen)
Suspect LG make the strips, but Vestel sell them cheaper on ChasHyde.
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Well, Chris, at least you know where the fault lies. Panasonic used to make a quality product, but seems they've gone down the road of depravity and are now peddling junk like everyone else.
It's hard to recommend any brand to punters requesting a word from the wise about best brand to buy.
Bruce
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Hi Bruce,
Gather this Panasonic Led supply works more on current than voltage - Seems sensible but then it doesn't realise when several Leds have gone S/C, and only notices when one has burned out the strip print where the supply voltage goes wild.
Thought this time to try remove/replace Leds without removing the strips as it's such a fag. Taking them off with hot air is no problem, but thought try fashion a soldering iron flat copper bit (Flatten a bit of water pipe) Braze to a short round bit then introduce under the strip with Kaptan tape on the underside to provide some insulation from the housing.
Downside might be that you can't remove the bit 'till the solder has set, but with LMP it might not be a problem - Will see - Chris.
As to your 'Words to the wise' - There are a few firms giving a five years' guarantee in the UK. Wife bought a 'One's Pad' that failed, and with such an assurance, and has now bought a 'One's Pad Mini' as the firm offering the guarantee, don't actually mend 'em, but shove 'em out to folks who don't mend 'em either.
Had a comeuppance trying sort Apple I Pods, where after getting a few duff ones from the Flea, found couldn't sort as the flexies broke no matter how careful I was. Then if sorted, there was the wheel that didn't work, even with half a credit card stuffed underneath, as suggested.
Guess slim modern stuff can be troublesome