I'm an EE, and would like a technical explanation from someone who understands the inner workings of an LCD display.
Just recently acquired a VERY nice looking 24" LCD display (Westinghouse L2410NM) for free. It could be important to note that this model uses an MVA panel, and not a TN like most other monitors. The acrylic panel on the corner was shattered when I got it, so I neatly removed it. I started enjoying the display for a few days until the nightmare began...
First the symptoms: After a few hours of powering up (but not always?!), the rear circuitry and top area of the LCD gets very hot, way hotter than I'd expect from an LCD. From the heat rising up, I would estimate something is hitting around 60C in there. The backlights are located on the far left and right sides, and they are not the source of the heat in this case. There is no fan, just grilles to passively dissipate heat. The mains power supply is integrated into the back of the LCD. I noted an audible high frequency noise that starts as soon as power is applied (without actually turning the monitor on), but that noise is apparently normal for this LCD model. Once it gets hot enough (sometimes it will not heat up at all and run for 24+ hours), the image starts distorting vertically, with horizontal black lines appearing randomly throughout the image.The distortion is the most severe at the bottom, and a chunk of the top area remains somewhat visible. Moving the mouse around shows that the screen is still refreshing at 60Hz. Soon after this (30 sec to 1 min), the entire image fades slowly and ghosted afterimage of the previous colors appear, which seems to eventually turn to orange. Image:
After first seeing all this nonsense, I went ahead and tore the thing apart. My targets were the 2 FPC cables at the top feeding the image to the panel - I reseated them to the best of my ability but this did not change anything. Mind you - I've tried all the obvious: swapped video cables, checked AC line voltage/ripple, changed output sources, used different inputs on the LCD, etc. The only thing I didn't try was forced cooling, but isn't that a little ridiculous?
My guesses:
*There is a history of abuse, so the problem is likely to be physical and not due to a faulty component. *Possibly damaged FPC cables. *Poor voltage regulation from the power supply (seems unlikely b/c of the effect of pressing on the top). *Cold/loose joint in the power supply. *Loose BGA connection on the video processing board (I hate BGA's, personally). *Cold/broken SMT solder connections on the ZIF connector that feeds the LCD panel itself. *Broken flexible cable feeding the pixels themselves (worst case scenario!).The only consistent signs I see is that pressing at the top usually alleviates the symptoms, there is a lot of heat present when the image does fail, and leaving the LCD unplugged for some time will always clear it up.
I work at a decently equipped shop (oscilloscope, decent DMM, heat gun, etc) with plenty of spare components and I can solder even tiny SMT pins without a problem, but I'd love some insight as to where I should poke around before I take the effort to haul it over to the shop. If my effort is futile it would save me a lot of headache to hear that. I know there must be at least someone out there has seen this before.
Thanks!
-JD