42lg5000

[dazw]

hi, my tv 42lg5000 keeps popping fuse in plug, when i opened tv up, and plugged it in, i get a spark from one of the yellow covered coils on the psu and this blows the 5 a fuse in the plug. do i need new psu ???
thanks.

[tom66]

Re: 42lg5000

Depends how competent you are in debugging power supplies but I'd expect you could easily identify the faulty component with a multimeter, as the component will appear to be shorted.

[dazw]

Re: 42lg5000

hi, i dont know much to be honest, i have repaired 3 of these tvs by replacing blown caps. but this one, the small fuse on psu next to power input was blown, so i fitted new fuse, as i put the mains cord in, i got the spark from what i think is one of the transformers ?? and it blown fuse in the mains plug, but it did not blow fuse on psu, thanks.

[tom66]

Re: 42lg5000

hi, i dont know much to be honest, i have repaired 3 of these tvs by replacing blown caps. but this one, the small fuse on psu next to power input was blown, so i fitted new fuse, as i put the mains cord in, i got the spark from what i think is one of the transformers ?? and it blown fuse in the mains plug, but it did not blow fuse on psu, thanks.

Okay, but do you have a multimeter? The spark may have occurred due to the sudden interruption of current through an inductor producing a voltage.

[dazw]

Re: 42lg5000

yes i do have a multimeter. i did this twice and then thought i had better ask about it. if you can give me a list of checks and instructions, i can strip tv down again to perform checks.

[tom66]

Re: 42lg5000

yes i do have a multimeter. i did this twice and then thought i had better ask about it. if you can give me a list of checks and instructions, i can strip tv down again to perform checks.

Can you take a pic of the PSU?

[dazw]

Re: 42lg5000

i dont have a good quality camera for a close up pic, ive only got camera on my phone, is there any thing in particular you need to look at or is it part numbers you require ? thanks.

[dazw]

Re: 42lg5000

i try this pic

[dazw]

Re: 42lg5000

are the brown stains smoke traces ? they are only present on the psu.... no where else inside the tv ?...

[dazw]

Re: 42lg5000

as you look at the pic..... the spark / pop came from the right hand yellow block (bottom right of pic) each time i replaced fuse in plug. but the fuse in the psu (not present in pic) top right, did not blow even though when i first opened up tv it was blown. sorry if sounds confusing ??

[tom66]

Re: 42lg5000

That TV has clearly got very hot; the PSU PCB is brown in many places. Maybe it wasn't mounted the right way around for good ventilation. Heat kills electronics.

Simplest check:
- Replace fuse
- Check resistance on 200 ohm scale from blue to brown on the AC connector (must be unplugged!)

If you measure close to zero ohms, there's a problem on the power supply. For me to help you further with that, I'll need a picture of the bottom, usually green side.

If there's a spark coming from the yellow inductors on the bottom right, it would seem like a PFC problem. Also, the brown residue there could be conductive, so if it wipes off consider giving that area a clean.

[dazw]

Re: 42lg5000

ok i have fitted replacement psu board, tv fires up but i have a few coloured lines along top of screen and dark parts of screen, is there a menu i can go into to refresh screen ?

[tom66]

Re: 42lg5000

ok i have fitted replacement psu board, tv fires up but i have a few coloured lines along top of screen and dark parts of screen, is there a menu i can go into to refresh screen ?

Probably a panel or T-con fault.

[dazw]

Re: 42lg5000

here is a pic of the fault.

[tom66]

Re: 42lg5000

1. Does it only affect dark areas?

2. Is it in fixed patches or do the glitches move?

3. Does it affect the OSD?

If 1 and/or 2: not a panel fault - most likely T-con

If 3: if not most likely main board

[dazw]

Re: 42lg5000

hi thanks for reply, they are fixed patches and dont move, and they are there no matter the screen shade or colour, yes you can see the patches over the osd.
when you say main board, do you mean the lcd panel ?

[tom66]

Re: 42lg5000

hi thanks for reply, they are fixed patches and dont move, and they are there no matter the screen shade or colour, yes you can see the patches over the osd.
when you say main board, do you mean the lcd panel ?

No, main board means the main processing board - the one with the input connectors on it.

The LCD panel is probably faulty. Try applying a small amount of pressure to the patches - do they move? Also, if you look closely, do they appear to be composed of pixels, or are they independent of the pixel grid? (may be hard to tell on a 1080p set though.)