LG 42PX3RVA

Got a 5 year old 42 inch tv with this model number and leave it overnight on standby.

Got up this morning and there was no power.

Checked mains plug and internal fuse - both fine.

240 volts going into power supply PCB so I suspect this, especially a capacitor that appears to have slightly "bubbled" at the top.

Anybody any experience of this TV or this problem that could give me something to try and establish exactly what the problem is ?

Can you post a picture of this capacitor?
The tops often have ridges in them to weaken them at a certain point so if they go wrong and build up pressure they just split.

Capacitors bulging like this is one of the most common failures but it normally just leads to unreliable operation and added stress to other components down the line. You might be lucky and the output supply from the psu is so unstable the processor in teh tv wont run and so cant bring the tv out of standby. However I have seen cases where the extra stress has caused other components to overheat and fail.

gblades said:

Can you post a picture of this capacitor?
The tops often have ridges in them to weaken them at a certain point so if they go wrong and build up pressure they just split.

Capacitors bulging like this is one of the most common failures but it normally just leads to unreliable operation and added stress to other components down the line. You might be lucky and the output supply from the psu is so unstable the processor in teh tv wont run and so cant bring the tv out of standby. However I have seen cases where the extra stress has caused other components to overheat and fail.

Click to expand...

If I was lucky, how do i get the processor to run and bring it out of standby ?

If the capacitor has completely failed then the output voltage from the powersupply will be very unstable and could basically crash a processor.
In Sky HD boxes which often had this problem the first symptom was failed recordings or picture breakup followed by the box refusing to come out of standby.

The fix is to replace the faulty capacitor. This is not so bad as the ratings are written on the side of them and you can see if it has failed because the top cracks open, top bulges or the bottom bulges. There may be more than 1 capacitor failing hence why I asked for photos.

gblades said:

If the capacitor has completely failed then the output voltage from the powersupply will be very unstable and could basically crash a processor.
In Sky HD boxes which often had this problem the first symptom was failed recordings or picture breakup followed by the box refusing to come out of standby.

The fix is to replace the faulty capacitor. This is not so bad as the ratings are written on the side of them and you can see if it has failed because the top cracks open, top bulges or the bottom bulges. There may be more than 1 capacitor failing hence why I asked for photos.

Click to expand...

OK thanks for the info.

I will take a photo tonight when I get home from work.

In the meantime, here is what I found on Google for the same problem on the same TV :


I just fixed this very same problem. It is the capacitors that are the problem. I think that if you have some minimal skills with
soldering, you can fix this yourself. You just need to take out the system board, then the power supply parts are on the top right.
The bad capacitor(s) will be bulging at the top. The ones that go bad are 1000 microfarad 10 Volt, however you can replace them with
the higher 16 volt. I got the capacitors from maplins, 24p each. You just need to de-solder out the bad ones and then put the new
ones in and solder. Remember that the negative end goes on the side with the bold black part of the circle on the system board.
solder the 2 new parts in then just cut off the ends off the capacitors.

Would you agree with this ?

Sounds about right apart from getting replacements from Maplin.
I dont believe they sell the low ESR high temperature capacitors that you should use in power supplies.

RS Components are a good supplier but you need to make sure you get the correct type, voltage rating, capacitance rating, diameter, and pin spacing so it takes a bit of comparing to find a good replacement.

These power supplies work by pulsing current into the capacitor at high frequencies in order to keep the voltage topped up. The capacitor basically smooths out the voltage.
Due to the high frequencies and internal resistance in the capacitor causes it to heat up so a low effective series resistance (ESR) the better. Higher temperature capacitors are less likely to dry out and cope better in the high temperature environment of a power supply.