Proscan PLED4274A-B

[smuddge]

I was given this and another LG tv that I also posted about to repair for a relative.

This Proscan PLED4274A-B turns on, backlight lights up fine but there is no picture at all.

No visible damage to any of the board with this one either.

I don't want to spend 80$+ US for a new mainboard if this is some problem with the boards that run along the top that are tab bonded to the panel.

any images needed just let me know and I will post them up.

thanks in advance for any guidance.

[budm]

Re: Proscan PLED4274A-B

We do need the pictures so we can see if it has Stand alone T-con or LCD panel with integrated T-con.
You will need to check if the T-con is getting the switched dcV feeding from the main board or not.

[smuddge]

Re: Proscan PLED4274A-B

it has an integrated tcon.
sorry pic of whole tv attached.

is there a fuse I could replace or jump just to see if it is that causing the problem?

I haven't seen one with in integrated tcon before and by the sounds of it this tv is scrap if thats the case correct?

[budm]

Re: Proscan PLED4274A-B

The fuse will be on that long T-CON board in the panel.

[multimeter]

Re: Proscan PLED4274A-B

unusual for a 42" to have intergrated T-CON?,i thought these had standalone t-con

[budm]

Re: Proscan PLED4274A-B

They are trying to make it as cheap as possible and less serviceable.

[budm]

Re: Proscan PLED4274A-B

Please take good clear closed up pictures around the LVDS connector, the fuse should be closed by the connector.

[smuddge]

Re: Proscan PLED4274A-B

here is the requested pic. the fuse is the one with the K on it? if so i tested it with multimeter and it shows to be fine.

is there anything else i can look at on this integrated tcon that could be the problem and could be replaced inexpensively.

[Diah]

Re: Proscan PLED4274A-B

it has being repaired or tried to repair.. its crap... sorry..

[vinceroger69]

Re: Proscan PLED4274A-B

here is the requested pic. the fuse is the one with the K on it? if so i tested it with multimeter and it shows to be fine.

is there anything else i can look at on this integrated tcon that could be the problem and could be replaced inexpensively.

yes thats the fuse what dc voltage do you get on each side of the fuse

[ReeceyBurger123]

Re: Proscan PLED4274A-B

I bet you the fuse tests good and all the other voltages do. I had same panel with shorted tab bond driver causing no image at if thats the case not fixable Pure modern junk !

[vinceroger69]

Re: Proscan PLED4274A-B

As the tab bonds are at bottom i guess someone could of used cleaner on the screen which has ran down and damaged the tabs with corrosion etc we have saw a few on the site in the past or as you say a shorted tab bond driver causing it.

[smuddge]

Re: Proscan PLED4274A-B

upon further inspection i noticed a small burn mark on the plastic beneath the power supply above a fet listed as LP18n20 1211.

could this be the problem here?

[dick_barton]

Re: Proscan PLED4274A-B

Can you check the resistance of the Mosfet. It looks as though it may well be damaged.

[smuddge]

Re: Proscan PLED4274A-B

sorry not really adept at this stuff yet. still learning. how to do i check resistance of the fet? I have meter set to 200k ohms and it shows 10 from the 2 sides. is this correct?

[vinceroger69]

Re: Proscan PLED4274A-B

https://www.youtube.com/watch?v=RBJGOOTEwfU

[smuddge]

Re: Proscan PLED4274A-B

ya i don't think my multimeter works right then. set it to diode.
shorted all pins and followed the video. I get nothing showing with any combination of source gate or drain on any mosfets on this board.

my multimeter just shows a 1

[smuddge]

Re: Proscan PLED4274A-B

i would settle for just ordering one and trying it.
i looked on digikey for this part and i find nothing.

is the part no LP18N20? or is there another option that i could use in its place?

any info would be great.

[budm]

Re: Proscan PLED4274A-B

You can find out if that MOSFET is functioning or not in the circuit by checking the DCV on each pin of the MOSFET when TV is off and when power switch is activated.

[smuddge]

Re: Proscan PLED4274A-B

just wanted to update this for anyone else with this tv. it was the mosfet. changed it and it is working great. thanks for all the help here.

will post again soon. i have a few more tv's to look at.

again great forum great users and extremely helpful and friendly.

love this place