LG 50px4d sound but no image

[artois7]

Just signed up to this forum, seems great. I'll be contributing in the laptop section when/where I can as that's my speciality. I have never tried to fix a TV before but wanted a challenge.

So I picked up an LG 50px4d for £50. I figured it was worth it, as even if it's a write off, the screen at least is good and will get my money back.

Previous owner said the image stopped coming on every now and then, but turning it on and off a few times would get the image back. Then this slowly got worse and now it won't come on at all. Also said it's never been opened or serviced.

I removed the back and the first thing I noticed is connectors P1, P806 and P101 are empty. I'm pretty sure they *should* be connected to something. There is a humming on the TV when it's switched on coming from the Y-sus board. When the Y sus is disconnected, the buzzing stops, and a slight buzzing is noticeable on the powerboard. When you turn the TV off and unplug it from the mains, theres a long high pitched squeal coming from somewhere on the board, I would guess a capacitor somewhere?

On the Ysus, the fuse FS2 reads 0ohm and FS3 reads 0.4ohm.

Both heatsinks on the Ysus are cold, and the 2 on the Zsus are pretty much cold but you can feel a tiny bit of heat.

Pictures are not a possibility until tomorrow, but for now I'm fairly sure the Ysus is at fault. The white plastic tabs connecting the Zsus to the Ysus I can't remove, they don't pull out and don't appear to have locks on. I don't wanna pull too hard incase I break them...

I have a multimeter and I can do my best to test whatever you guys need..

[PlainBill]

Re: LG 50px4d sound but no image

Just signed up to this forum, seems great. I'll be contributing in the laptop section when/where I can as that's my speciality. I have never tried to fix a TV before but wanted a challenge.

So I picked up an LG 50px4d for £50. I figured it was worth it, as even if it's a write off, the screen at least is good and will get my money back.

Previous owner said the image stopped coming on every now and then, but turning it on and off a few times would get the image back. Then this slowly got worse and now it won't come on at all. Also said it's never been opened or serviced.

I removed the back and the first thing I noticed is connectors P1, P806 and P101 are empty. I'm pretty sure they *should* be connected to something. There is a humming on the TV when it's switched on coming from the Y-sus board. When the Y sus is disconnected, the buzzing stops, and a slight buzzing is noticeable on the powerboard. When you turn the TV off and unplug it from the mains, theres a long high pitched squeal coming from somewhere on the board, I would guess a capacitor somewhere?

On the Ysus, the fuse FS2 reads 0ohm and FS3 reads 0.4ohm.

Both heatsinks on the Ysus are cold, and the 2 on the Zsus are pretty much cold but you can feel a tiny bit of heat.

Pictures are not a possibility until tomorrow, but for now I'm fairly sure the Ysus is at fault. The white plastic tabs connecting the Zsus to the Ysus I can't remove, they don't pull out and don't appear to have locks on. I don't wanna pull too hard incase I break them...

I have a multimeter and I can do my best to test whatever you guys need..

The service manual can be found here.

A common failure on these sets is the hybrids on the sustain modules. I notice there are a number of sellers on eBay UK selling the Y and Z sustain boards at what Benny Hill referred to as 'Popular Prices' (popular with the seller, not so much with the buyer).

Before damaging any connectors, locate these two manuals: 13287511-Lg-Plasma-Tv-Full-Training-Manual and 7580885-LG-Plasma-TV-Full-Training-Manual (the numbers are Scribd numbers). They describe how to disconnect cables and to locate possible problems with the hybrids.

PlainBill

[artois7]

Re: LG 50px4d sound but no image

Thanks for the service manual, I can never get scribd to load past the first 3 pages. Any ideas?

Edit

Worked under IE. I'll have a gander.

[artois7]

Re: LG 50px4d sound but no image

Update

Unplugged a cable going from the Ysus directly to the Zsus board. This has resulted in getting red lines/sections across the TV. The lines appear in four segments, one on the left, one in the middle, one small thin one next to it, and then there's nothing on the right hand side of the screen. Then it resets. Sound still works.

according to the manual this indictates a faulty Zsus?

[artois7]

Re: LG 50px4d sound but no image

Update

Unplugged a cable going from the Ysus directly to the Xsus board. This has resulted in getting red lines/sections across the TV. The lines appear in four segments, one on the left, one in the middle, one small thin one next to it, and then there's nothing on the right hand side of the screen. Then it resets. Sound still works.

according to the manual this indictates a faulty Zsus?

Well I put this away for ages, and then came back to it as I had nothing better to do today. Carrying on from the above situation, I removed all cables from the X-sus board and switched it on. This resulted in the above result but a bit more mixed; ie more colours, some lines stayed on the screen whilst others continued the loop. But still nothing on the right section of the screen. I think one of the buffer boards which controls the right section is bust?

An ebay search then revealed a seller parted out a 50px4d with a smashed screen and had the X-sus up for sale for £30 + postage. Considering I get image without the X-sus connected, I decided to make the punt and spend the £40.

Hoping I haven't wasted £40. Although I'll just sell it on as it's cheap for the part. Will report back once I receive it.

[artois7]

Re: LG 50px4d sound but no image

Here are pictures at 1500x1500. The pictures of the screen show the result of having the X-sus unplugged completely. Having it plugged in results in a completely blank screen. Did I do the right thing ordering the X-sus?

[artois7]

Re: LG 50px4d sound but no image

Got the x sus and fitted it today. Noticed 2 components are missing from it but I'm not sure what they're called. This is a revision B and mine's an A, might be why they're not there?

Anyway, put it all in and turned on. Smell of burning. Shut it all off and rechecked all connections, powered it up and it goes into protect mode. Red, yellow, green, click, red. Unplugged X sus and it powers up fine. Plugged X sus back in and unplugged Y sus and it powers up fine.

Before when I would unplug the X sus, I'd get red lines across the TV. Now I don't.

Bad power supply? Shorted buffers? Bad mainboard..?

Edit

Just plugged everything back together, turned it on, and the lower IPM on the x sus went PING and now just clicks constantly. Guess that just blew up. Any ideas?