Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: call me al on March 24, 2019,15:44:46
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hI all Am struggling with this Pan tx48cx400b Fault is backlights flash on for a second and go off,have checked leds all seem ok.Psu is the 17ips20 so am suspecting it but not sure Any ideas very welcome Thanks again
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Hi Al,
Don't know the 17ips20 power supply, but 90% of failures are caused by backlight LEDs.
If you used a LED tester, it can't entirely be relied on, eg, it may light up a strip with a shorted LED at the low current it operates on, whereas in normal operation in the tv at higher current, the protect will be activated. The LED tester lacks the same protect circuit and will keep the strip alight forever.
My gut feeling is backlight LEDs, but you'll have to strip the display panel to know for sure. Piece of cake and peace of mind.
Bruce
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Iv exact same model and all leds are fine. I think its power supply but it looks like I need the exact psu to check it. Mine runs for 10 mins then goes out. Others online complaining of same symptoms
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hi if the voltage is low on the filter cap, if the reading is 335v the mosfet as shorted
shaun
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Hi All A big thanks for all replys especally to Bruce for being bang on with his ,it was exactly as said went back and re checked leds and found 3 shorted replaced them and on it came.My next problem was trying to get lenzs to fit properly to get red of halo effect ,have only been moderatly sucessful at this .What glue is best to use as have yet to get on that works right.Anyway thanks again be lost without this forum :93:
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Hi Al, I've been using brush-on superglue to date - it dries quickly with a bit of downward pressure. Comes in a small plastic bottle - a bit like nail polish - and doesn't go off like those little tubes of it. I've purchased some UV glue pens but have yet to try them.
Thanks for the feedback. Bruce
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Well, I got my chance to trial the UV glue on an LG where the LED covers fall off. It worked a treat - 5 seconds of UV and the glue hardens. It's ideal for LEDs because they're transparent and the UV light can reach the glue spots.
Only drawback is the light switch - it can be easily knocked to the on position and flatten the 2 button batteries inside. Of 4 pens I have, only 2 now work because of this. Now thinking of using a UV light unit from a robot vacuum cleaner, which is larger and can be powered external power source. Bruce
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Hi Bruce,
What do you use if you've changed a Led and get a screen halo ? Original holes don't work, so need glue lenses for minimum halo with a bit of the first layer plastic sheet to check.
Tend to use a water based glue, as it's flexible and doesn't contaminate the light path.
The other day got a 50 LG with the issue, but didn't notice that one side flexie was attached to the frame. On gentle lifting it tore off with it's chip - Merde. Seems on the set, all side flexies were attached with White tape, but five had fallen off.
Thought though to sort the Leds for the next time - Chris.
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Hi Chris, I get your drift, but on this one it only had the LED caps dislodged. Even so, it seems to me that the caps have some kind of light bias which I haven't comprehended yet The large LG caps appear to have a flange on the top circumference, but the pattern eludes me.
The halo is an irritating problem and yes, best to check each one with the thick sheet in place. At least the cap can be prised loose again and reseated. Have encountered TVs where side tabs are taped down, but my worst one was where the entire bottom of the glass had been glued on.
Suffice to say the Stanley knife worked but I nicked the glass in one spot, and that was the end of that. Bruce
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Hi Bruce,
Just had a 42 LG where all 32 Leds were duff, mostly S/C. Thinking about knocking up a small oven to the purpose using LMP Lead free paste as guess max 150C will do little harm.
Also had a 50 LG with just one tab taped down. Natch didn't notice 'till it tore off - Life's Good - Chris.