Riddled TV Repair Forum

SchaefZ28 · Joined: 08 Nov 2015 Posts: 5 Location: St. Louis

Ok guys & girls, hopefully you can help out. Replacing a lightbulb in a Samsung DLP is the extent of my TV repair experience, but I like to think I'm a pretty handy guy.. Now I've picked up a 7 year old 52" LCD freebie with a bad picture.

The TV in question is a:
Brand: Philips
Model: 52PFL7403D/F7
Chassis: LC8.1U LA

The original problem is that the picture from any input (game console, antenna, cable) is highly solarized. The menus and a blank blue screen look great. After some research, I was lead to believe the culprit was a bad main board.

I purchased a used main board from ebay and installed it, and now I am getting different symptoms that before. With the 'new' board, the left half of the screen is black, and the right half of the picture is distorted (as our friend Luigi will demonstrate in the following pictures).

My question to you all is twofold:
Is the solarized picture from a bad main board?
Is the 'new' main board from ebay bad as well? I am leaning towards a bad top LDVS cable mount, because using my original main board, if I unplug the top LDVS cable, the left half of the screen goes black. If this board is in fact bad, I need to prove it in order to get my money back..

Here is the picture with the original main board, using an old Nintendo64 for input (AV Cables).

Original main board - showing blue screen and menus:

Now here are similar pictures with the 'new' main board installed:

For good meanure, here's a full shot of the back of the TV, a picture of the model information, and a closeup of the main board.

Google

kuhurdler · Joined: 28 Dec 2006 Posts: 2878 Location: Overland Park, KS

If you're certain that your cables are seated correctly on the top left corner, I assume that the new mainboard is bad. I think it is more likely that you have a bad Tcon board.

SchaefZ28 · Joined: 08 Nov 2015 Posts: 5 Location: St. Louis

The LVDS cables are definitely seated correctly, I have plugged and unplugged them a few times to see if I could get any change on the screen.

Out of curiosity, what is your reasoning to suggest the T-Con is bad?

The picture is only messed up when there is an input, which to me would seem to suggest a bad signal from the main board (where the input is received) to the T-Con. Does the T-Con process inputs signals separately from internal tv signals (menus, blue screen, etc)?
With the tv on, if I unplug the LVDS cable on the top of the main board, the left half of the screen goes black. If I unplug the LVDS cable on the side of the main board, the whole screen freezes. - which is what makes me think the 'new' main board has an issue with the top LVDS connector..

Any troubleshooting suggestions?

kuhurdler · Joined: 28 Dec 2006 Posts: 2878 Location: Overland Park, KS

I reread your post and realize now that the menu screens appear normal. Based on that, I think your TCon is fine. Sorry I overlooked that before. I think that both your new and old mainboards are probably bad.

Don't assume an unscrupulous seller. Perhaps the new one was damaged in shipping. Give the seller a chance to make it right.

SchaefZ28 · Joined: 08 Nov 2015 Posts: 5 Location: St. Louis

Thanks for the reply. I'll look for another main board, and hopefully that will take care of my problem.

Google

SchaefZ28 · Joined: 08 Nov 2015 Posts: 5 Location: St. Louis

Third main board, and different symptoms again. This is driving me crazy.
As with the second main board - it's the left half of the screen with the problem, except this time the picture is distorted and jumbles around rather than staying stationary.
At this point am I looking at a bad LVDS cable, or bad Tcon?
It seems highly unlikely I was sold 2 bad main boards..
I am just not understanding how the menus can look fine if the Tcon/cable isn't working right?
Another observation I just made: while on a blue screen, everything looks fine - until I pressed the mute button, it made the left half of the screen shudder & distort for a handful of seconds until the mute icon in the upper left corner went away..

Any ideas?
I hate throwing parts at it hoping for a fix.. It's beginning to be an expensive 'free' TV.

SchaefZ28 · Joined: 08 Nov 2015 Posts: 5 Location: St. Louis

Ok, today I had been checking voltage at the top LVDS cable and not really figuring anything out.. Turned the TV to the right input and it was working correctly! No idea what is different now than before... but I'm not going to complain too much. I put the back cover back on and hooked up the antenna cable, and the regular channels are showing correctly as well.

Before I closed it all back up, just for good measure I unplugged both LVDS cables and plugged them back in to see the same results. Then to check the first main board I purchased, I hooked it up and also got the same results as before (half black screen) so I am pretty certain the first board is bad.

kuhurdler · Joined: 28 Dec 2006 Posts: 2878 Location: Overland Park, KS

That is really odd. Glad you got it working. Hope it stays working.