# LG PT-53A83T SMPS Fuse blowing



## martaroony (Apr 13, 2012)

Hello, Fellow Home Theater Shackers,

As you might have guessed Im new to the forum, and after trolling the site looking for an answer to my TV woes , have decided to have a go a posting to try and get to the bottom of my Problems.

I have an LG rear Projection TV that I have had for some years now, some would say why do you bother with it , ( the wife mainly) " why not buy a new Panel screen" . But , I have a connection with this TV as I have fixed it once before , by researching the problem here on this site , Buying the parts , ( STK chips) and soldiering them in , and have had years of good service since.
So Im reluctant to just give up on it as its served me well.

So here it goes, I'll relay to your expert minds as best I can what the symptoms are, and see what suggestions we come up with , and with a bit of luck it wont be outside of my expertise with the soldiering Iron.

Firstly, The Model, LG PT-53A83T (Australian Model) approx 11 years old.

Previous fix , 2 x New STK 180 IC Chips.

Current Problem : 

Last time the TV was turned on by the remote , it made quiet a speaker based destorted noise.
Then there was no stand-by light on the front panel.

So , my first thought was to remove the Power Board, and inspect , On doing this I noticed the 
little 5A /250 V Fuse had blown.

Optomisticly, I grabbed another Fuse hoping this may have been a too good to be true easy fix.
On replacing the fuse ,and switching the power back on to the set, The stand-by light was back on, So once again pushing the Power -on button on the remote blew the fuse again, So it sounds like there is a short some where in the switching side of the 240V , ( Thats our mains power here in Aus).

Now , one last observation Ive made on removing the SMPS Board is that on the underside, (printed circut side) there is a line that runs through the centre of the board , and on one side it reads "Cold' , and the other side reads "HOT", Now , on the COLD side there is a 4 legged component (D845) screwed to an alloy heat sink, which is the only thing on the entire board which looks like it has got hot enough to melt some of the resin coating over the soldier,.

So I dont know whether thats normal , but its the only thing I can visually see , considering it says its on the cold side on the board.

So Fellow Shackers, any help would be good, and input would be muchly appreciated.:whistling:


Thanks for reading the post, Regards Martaroony.:neener:


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## mechman (Feb 8, 2007)

Did you get this sorted out yet Martaroony?


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## martaroony (Apr 13, 2012)

Hey Mechman, thanks for your reply, and no still going with it.

I did get a little advise from a retired TV service man, however it was very general advise.

I obtained the caps that he said he would change, purely as they are inexpensive and can cause problems, and one Switching Semi Conductor,Which appeared to be a dead short.

It was promising for a while, the stand by light was on , then on switching the TV on the normal click of it powering up, then after a while ,, One of the Varitors blew up.

So Im back to the start, Ive removed the Varistor, and CE 400V 470UF Smoother, and a couple other resistors in the general area. that were possibly damaged with the heat.

So now Ive decided to test every thing before I spend any more money on parts , incase ive Got bigger problems.

So my first step is to pick up my Multimeter , and get some advise on how, and what to test.

Ive downloaded the schematics on the set ,So I have a fair idea on what parts are what now.

So It will probley be a slow process , I would say.

What I will try and do is Photograph the board currently, so you can see what components Ive removed.

Thanks again ., Martaroony.:sweat:


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