LG 50PQ30 Vertical Red Lines and Residual Image

[drpj23]

Ok, so the issue with this plasma set is once initially cut on, you have some foreign artifacts on the screen but everytime the "No Signal" bar moves it leaves a little trail as well as the menu. It gets worse as you leave it on and after about 3-5 minutes, it turns into the picture I have included.

Voltages on the P/S look good but the 15v off the Z-SUS is about 17 if that is of any deal and the -VY voltage was positive. I put the correct leads where it said + and - and for the other voltages is was correct but this was positive.

Tried re-seating connectors in the Y-section but to no improvement.

Read that some had replaced buffers with line issues (but mine seems a bit more severe than those)
One place said Y-SUS, which kinda makes sense due to it warming up and getting worse.
And finally, my initial thought was the controller board perhaps.

[sam_sam_sam]

Re: LG 50PQ30 Vertical Red Lines and Residual Image

Do you have a ESR cap tester if you do I would be checking all of your caps

[drpj23]

Re: LG 50PQ30 Vertical Red Lines and Residual Image

I do and where would you recommend to start looking?

[drpj23]

Re: LG 50PQ30 Vertical Red Lines and Residual Image

Well, no offense, but time does not allow me to really check every single cap on this thing. The 17v is standard running voltage (although it says 15v) but still confused about VY.

I might as well take a stab in the dark with the Y-SUS due to the Horizontal line (yes it says vertical in the forum title.....my bad lol)

[drpj23]

Re: LG 50PQ30 Vertical Red Lines and Residual Image

Ok, I found out -VY will read positive....since all voltages are checking out on the Y SUS should I be weary of Z?

[tom66]

Re: LG 50PQ30 Vertical Red Lines and Residual Image

Y and Z sus can't create digital noise. They only make the screen light up.

The only boards that can create such noise are the PDP T-con board, buffer boards, column drivers (non-replaceable - bonded to panel), and main board.

[drpj23]

Re: LG 50PQ30 Vertical Red Lines and Residual Image

That makes sense for the uniform horizontal red lines I can see that being controller (TCON) or buffers.
How would the column drivers come into play?
The image retention though, do you think that is power related to the sus boards. (Got that from another post that is going on right now)

[tom66]

Re: LG 50PQ30 Vertical Red Lines and Residual Image

That makes sense for the uniform horizontal red lines I can see that being controller (TCON) or buffers.

In a plasma display, the column drivers load the data in from the bottom of the panel. If the column drivers all successively fail (which I admit is very, very unlikely, unless something managed to damage them all at once) then they could load in random data causing the weird lines. The buffers are only responsible for selecting the right line to load new data into (the panel is "programmed" then sustained - the cells which have been programmed ON are made to light up), so if they load the wrong line or at the wrong time, it can cause a similar scrambled picture effect.

However, I notice the panel is mostly red, which would make me suspect the control board more, as the buffers and drivers are rarely selective.

The image retention though, do you think that is power related to the sus boards. (Got that from another post that is going on right now)

Possibly a bad control board not sending the appropriate erase signal to the panel to make it remove the previous image. All plasma panels are primed (prepare cells to emit light - this is what causes them to glow when set as black), written to, "sustained" (made to light up) and then erased.

So now I think about it more, I suspect the control board, and eliminate my other suggestions.

[drpj23]

Re: LG 50PQ30 Vertical Red Lines and Residual Image

Alright, thank you for the insight, I will try the controller board and report back.