Philips 42PFL9803 - Panel fault case study - vertical colored lines - black and white blocks in image

There is a lack of interesting TVs on eBay and eBay classifieds these days. It seems as if people only break their stupid thin-frame panels with kid toys or tip over the thing. Frustrating.

I found this Philips, a model I successfully repaired once, and gave it a shot. Maybe I could get lucky and it was the same fault. The seller said it would not produce an image at all. At pick-up time he told me that he got the TV from someone else who said it produced lines in the image. Damn it! I would neither buy stuff from a re-seller who never used the device, nor TVs with lines in the image - if I knew it.

Okay. Turned the device on. The activity indicator at the bottom flashed, which told me that booting was in progress. No image appeared and then the relays of the power supply clicked and the set went off. No blink code was emitted from the stand-by LED. That's not good. After checking the FETs on the main board voltage regulator section, which supply the main processor (those fail often in this model), I shorted the SDM testpoint on the main board to ground to activate the service default mode. In this mode, some safety checks are overridden. And I got an image:

Let's analyse this for a moment:
- The half-half characteristic would indicate a TCON failure, Same goes for the black block to the left. The right side shows no errors. It is just blank.
- The striped block however rather looks like source driver failure in the panel.

Look at this detail. The image had a kind of frame around it. The rounded corners looked funny:

As this was all around the image in perfect symmetry, I did not book that on the panel faults account.

So, the diagnose wasn't clear at all. The next experiment in such cases is to disconnect the connectors from the TCON to the panel one by one. Oh crap, the TCON was buried under the sub chassis on which all the other stuff was mounted. Thank you, Philips! :-(

Removing the chassis wasn't as difficult as it seemed:

The panel unit without the sub chassis. The TCON cover exposed:

Now I disconnected the left side:

And got this:

Hmmm, this really looked like a defect source driver! A panel cannot produce any patterns on the side where the connector isn't attached. Alas, upon close inspection of the TCON I noticed that some traces go across from the right control side of the TCON the left panel source drivers. And why was the right side still blank? Argh! These things are still a mystery to me.

Now left side back in, right side disconnected:

This is all so weird. The right side is disconnected and the image to the left changes. There were clearly some cross-effects, which I do not understand.

The lines looked interesting:

I did not get one single step further! It could still be the TCON, with a tendency to panel fault. On eBay the seller @loeterotto, who specializes in TCON boards, had the matching board and so I bought it to find certainty. Alas, the new board produced the same image. I returned it.

Right, so this TV is junk. At least the main board seemed to work fine and it is very rare. I have a chance for a good price.

While dismantling the panel, I finally found the reason for the fault. Two broken flat cables, where the source drivers are embedded into. So my first instinct was right.

LCD panels. I still don't understand how to reliably diagnose those suckers!

Here is an picture of the direct LED backlight. This was so much better (and more expensive) than the cheap crap that Samsung and LG produce these days. A vast array of less powerful LEDs is much more reliable then a small number of high power LEDs, which die after three years due to overheating.