Lg 50PQ3000

[ReeceyBurger123]

Hello I have this 50" lg plasma in, I had to repair the psu by replacing the main bridge rectifier and fuse. All the voltages (Va&Vs) are perfectly in spec but after the tv has been on for a while the screen will go black with lots of sparkles on the screen, when it does this you get locked out and cant do anything but turning the tv on and off solves the issue and the cycle repeats. Nothing it obviously leaky or out of spec just need a pin point on where to start checking never seen a plasma do this before any ideas is much appreciated. I will upload a youtube video showing what the tv does the link will be provided under this thank you.

[freakaftr8]

Re: Lg 50PQ3000

Does the power supply volrages start to drop off while this happens? especially look at VS voltage. Could be a YSUS issue. What's vscan doing on the YSUS when this starts to happen ?

[ReeceyBurger123]

Re: Lg 50PQ3000

Hi all the voltages are constant and in spec nothing drops out, the ysus does make a ticking/hissing noise when it does so starting to point to there Im just uploading a yt video of whats happening.

[ReeceyBurger123]

Re: Lg 50PQ3000

Here is the link to the video https://www.youtube.com/watch?v=yrqaF7Kh41I

[ReeceyBurger123]

Re: Lg 50PQ3000

Will try heating the boards with a hairdryer, then certain areas guessing that the y sus is bad.

[ReeceyBurger123]

Re: Lg 50PQ3000

Heated y sus and that is causing this issue, will try heating certain areas to find whats going bad.

[mmartell]

Re: Lg 50PQ3000

Does this ysus have an ipm ?

[ReeceyBurger123]

Re: Lg 50PQ3000

Does this ysus have an ipm ?

No it doesn't, I will give you all the model numbers of the boards when I get back to that tv. I haven't checked all the transistors and mosfets but nothing obviously leaky will get back to you later.

[ReeceyBurger123]

Re: Lg 50PQ3000

Just got back around to this tv, I took the approach of heating the ysus and seeing if anything goes open when hot not shown up but the ve resistor seems to be burnt and that voltage drops out when the fault occurs I will take photos and get testing.

[ReeceyBurger123]

Re: Lg 50PQ3000

Replaced the ysus but same thing guess the x/zsus is out, found two bad resistors on zsus going to now replace that.

[tom66]

Re: Lg 50PQ3000

It is rare for resistors to fail, without something else in the circuit going wrong. Resistors also very rarely fail intermittently - they can overheat and open-circuit, but that is a fuse-type failure. It's not impossible, but it's unlikely.

[ReeceyBurger123]

Re: Lg 50PQ3000

It is rare for resistors to fail, without something else in the circuit going wrong. Resistors also very rarely fail intermittently - they can overheat and open-circuit, but that is a fuse-type failure. It's not impossible, but it's unlikely.

I measured them wrong I used the diode tester lol, after further testing found the control board to be at fault theres an 8pin ic that when heated goes open. Ordered a new control board, already £80 on a ysu now £10 on a control board, hopefully sort this junk.

[tom66]

Re: Lg 50PQ3000

Your continued fascination of throwing boards at this set with very little diagnosis astounds me. Stop, and think about it for a second. What does an IC failing open when it gets hot mean? The kind of failure you describe is POSSIBLE, but it is UNLIKELY. Does the control board turn off when the fault occurs? Have you checked the linear regulators on it? What about tried pressing on the BGA?

BTW, you should be careful swapping over the control board, as the hour counter will be out of sync, potentially causing panel maldischarge.

[ReeceyBurger123]

Re: Lg 50PQ3000

Your continued fascination of throwing boards at this set with very little diagnosis astounds me. Stop, and think about it for a second. What does an IC failing open when it gets hot mean? The kind of failure you describe is POSSIBLE, but it is UNLIKELY. Does the control board turn off when the fault occurs? Have you checked the linear regulators on it? What about tried pressing on the BGA?

BTW, you should be careful swapping over the control board, as the hour counter will be out of sync, potentially causing panel maldischarge.

I will make a youtube video with a FULL explanation on how I diagnosed this because right now I cant be arsed to because this thing has brassed me of enough, I will put a link to the video later.

[ReeceyBurger123]

Re: Lg 50PQ3000

Sorted it, was the control board I decided to replace it for £8 rather than buying the chip needed which was £3 because something els could have been wrong, the tv works great now will put a link to the video when its ready.

[ReeceyBurger123]

Re: Lg 50PQ3000

Right as promised here is the youtube video explaining this tv.
https://www.youtube.com/watch?v=S6HtIBgFiYk