Samsung LE37A456C2D - image retention issue

[noledud]

Samsung LE37A456C2D - image retention issue

37 LCD got it with no sound and hdmi plugs bent ( quite a mess )

manged to make the bent pins good on the HDMI sockets and got the picture working but still no sound - it said feature unavailable when you tried to turn up or down.

Did a factory reset and that brought the sound back

TV works but it has terrible image retention and you can see the refresh rolling down the screen

tried all settings and nothing has made it any better

Now iv read it might down to it being a cheap panel but unable to find any sticker on it - in the service menu it has it as chu ?

please see the pics - could the t-con or main be causing this ?

[noledud]

Re: Samsung LE37A456C2D - image retention issue

its the same on all inputs

[tom66]

Re: Samsung LE37A456C2D - image retention issue

I'm guessing CPT / Chungwha panel, this is pretty much par for the course for them. You can check TCON board VCOM voltage, low or high VCOM would cause this effect but it cannot always be adjusted. It will also cause the odd/even pixels to flicker which I think I can see in the photos.

[noledud]

Re: Samsung LE37A456C2D - image retention issue

so do the panels do this with age tom as im sure it couldnt have been like this new ?

[tom66]

Re: Samsung LE37A456C2D - image retention issue

They do get worse - the VCOM adjustment drifts and needs to be set back - it's usually on t-con or panel board. Post a picture of them if you need help locating it.

But it would have been pretty bad from the start anyway, CPT panels are the WORST there are. Interestingly note the name stands for Chungwha Picture Tubes as they used to make CRTs so were in a bit of a panic when the market dried up and rushed their panels to market.

[noledud]

Re: Samsung LE37A456C2D - image retention issue

ok cool at work at the mo so will check out the t-con tomorrow, i didnt know you could adjust anything on lcd's - fingers crossed

[noledud]

Re: Samsung LE37A456C2D - image retention issue

Hi tom and all i have stripped it down to the tcon and bottom of the LCD

how do i measure the VCOM and adjust ?

[tom66]

Re: Samsung LE37A456C2D - image retention issue

Looks like an AUO panel, huh. Not normally known for this. Anyhow, that potentiometer is the adjustment. Can you see points marked VCM/VCOM/VCO and AVDD? The VCOM should be half AVDD within about 0.2V.

[noledud]

Re: Samsung LE37A456C2D - image retention issue

befor i mess could it be anything to do with the factory reset i did ?

[tom66]

Re: Samsung LE37A456C2D - image retention issue

The best pattern for adjusting VCOM is this. You should adjust it for minimum flicker - it will still flicker slightly, but get it as low as possible.
http://www.techmind.org/lcd/

I'd select pixel dot inversion or line paired pixel dot inversion. Full screen on VGA with "JUST SCAN" turned on (in aspect ratio settings) - you want absolutely no scaling and to have exact panel resolution.

Factory reset would not affect it.

[noledud]

Re: Samsung LE37A456C2D - image retention issue

also are the mesure points on the t-con or the board with the potentiometer ?

[noledud]

Re: Samsung LE37A456C2D - image retention issue

ok i get it, have to rebuild the tv but missing the bottom section so i can adjust ?

[noledud]

Re: Samsung LE37A456C2D - image retention issue

can i adjust while powered on or do i have to turn off adjust then back on ?

[tom66]

Re: Samsung LE37A456C2D - image retention issue

Adjust while on - you want that pattern up and to be looking at it while doing the adjustment to find the best point.

[noledud]

Re: Samsung LE37A456C2D - image retention issue

not making any difference tom now im being thick but where do i check the aspect ratio settings?

[noledud]

Re: Samsung LE37A456C2D - image retention issue

the option for just scan is grayed out

[tom66]

Re: Samsung LE37A456C2D - image retention issue

You need to do that sometimes via HDMI.

[noledud]

Re: Samsung LE37A456C2D - image retention issue

i havnt got hdmi out on my laptop or computer

when i did try adjust it i didnt notice any change with the ghosting what so ever

could it be a main board prob or tcon ?

[tom66]

Re: Samsung LE37A456C2D - image retention issue

I would say panel then t-con. TBH I have seen this problem before on LCDs but never tried to fix it. VCOM adjustment should help with the flickering and image retention but no guarantees.

[noledud]

Re: Samsung LE37A456C2D - image retention issue

i havnt got hdmi out on my laptop or computer

when i did try adjust it i didnt notice any change with the ghosting what so ever

could it be a main board prob or tcon ?