LCD monitor repair

[exdeath]

Westinghouse LVM-37W3.

Connection via DVI.

Went out on me last night. As I was typing, the screen did a pixelated wipe to black from left to right that took about two seconds.

No video signal to the panel at all on any input, not even the self generated OSD menus, input source, "no signal", nothing. The backlight is visible, and adjusting backlight intensity changes the brightness of the screen, so obviously it's not a classic backlight or inverter board problem. It appears that the image data itself is no longer making it to the LCD panel and that whole panel is defaulting to it's "on" state (eg: black).

Short of checking the actual display processing board for blown capacitors or reseating various ribbon cables, any ideas? No smoke or abnormal heat or smell or anything detectable. Have yet to crack it open.

Anyone experienced with electronics/LCD repair ever experienced the symptom of the screen actually doing a gradual fade/wipe when going out? It appeared as though a ribbon cable slowly pulled out of it's socket and wiped the screen as rows and columns unplugged from one edge of the cable to the other, but I know there is no such cable and that data is sent serially and that the glass panel itself has it's own microcontroller much like a keyboard controller to actually address rows and columns.

 

[BassBomb]

does it have any other types of connection? try those?

try a different object with the monitor to confirm it is the monitor

 

[exdeath]

does it have any other types of connection? try those?

try a different object with the monitor to confirm it is the monitor

It's definately the monitor and either the panel itself or the input board. Had a Sega Genesis on S-video also not do anything. Hitting the menu key does not display anything, and cycling inputs will blank the screen and change to the preset backlight level for each input, but no data display, including the internally generated on screen display overlay that indicates input selection, etc.

Given that the self generated always native res overlays don't display either, that rules out input processing or scaler; it's definately between the logic board display final output and the panel itself.

 

[exdeath]

Took a look at it this evening. No evidence of damaged components. inspected and reseated all cables, from the LVDS cable from the main board to the LCD controller and the LCD controller to the plastic ribbon cables that go to the perimeter of the LCD matrix. Didn't appear to be any separation of the delicate ribbon cables from the edges of the LCD at any point.

Still no signal to the screen, meanwhile the monitor itself appears to be functioning perfectly fine (plug something into it and the backlight flickers and auto switches to that input and plays audio, but the screen remains pure black).

I wonder if the LCD controller board itself went out, or if a sealed edge of the panel itself just gave out and the panel delaminated itself or something; the way it just dissolved to black from left to right (random pixels, not columns) like a special effects fade was pretty weird.

Genesis gm1601h-lf image processor, there are 6 diagnostic leds on the board, 4 in the middle constant on, ones on the edges blinking randomly. Have no clue what they are or what sort of status they represent What happened to the days when electronics were shipped with full schematics?

 

[PottedMeat]

Genesis gm1601h-lf image processor, there are 6 diagnostic leds on the board, 4 in the middle constant on, ones on the edges blinking randomly. Have no clue what they are or what sort of status they represent What happened to the days when electronics were shipped with full schematics?

Can you find the image processor datasheet?

Looks like Genesis was acquired by STMicroelectronics - http://www.st.com/stonline/products/families/tv_monitors/tv_monitors.htm . They've got a few of the part numbers but not a GM1601.

If you can find the datasheet, there's probably also a reference board schematic and manufacturers usually don't deviate too much from that - maybe that's a starting point.

 

[exdeath]

Update, with everything apart, hooked something up to it and just let it sit there and see if cold/heat cycling was the cause, even grabbed the corners of the chassis and gently flexed the panel a little. After less than an hour, the front LCD glass itself was hot to the touch. Presumably being all black it's staying at 100% duty cycle in the ON mode for every pixel and soaking current for 2 million pixels; which in turn indicates that the panel itself is probably working and just doing what it's told. Panel defects with contacts and de-lamination or cracks usually have solid rows and columns missing or chunks of image missing or discolored.

Leads me to believe it's the way the controller is driving the panel and that the panel itself must be fine if it's uniformly black and heating. It's a AU Optotronics driver board/panel assembly. Only problem is nothing looks wrong externally and for solid state components to just fail randomly is rare.

Tapped around on the Genesis processor too while it was running to no effect; all too aware of BGA contacts separating.

http://cgi.ebay.com/WESTINGHOUSE-LV...emQQptZLH_DefaultDomain_0?hash=item3ef9d69443

Not sure if it's worth the risk of throwing away $50 or just grabbing a new 40" LED backlit display.


Problem is 37" is a perfect sweet spot for a desktop display and that size is rare, much less something suitable for a PC monitor that doesn't have a huge bezel and speakers and stuff. Definitely want flexible inputs and a scaler with split screen so the 30" PC monitors are out of the question; I do quite a bit of non PC dev work and it's nice to be able to plug in anything I want from any source.

 

[Zacharry]

You should be able to add a new controller to the monitor. I was in the process of doing that to my 22" until I realized that the LCD was destroyed at the point of impact. (Girlfriend has temper issues and she hates technology).

 

[santz]

are u sure, its the lcd monitor and not your graphic card. have you tried to input another source to the LCD or have you tried to connect your pc to another tv??

 

[slag]

are u sure, its the lcd monitor and not your graphic card. have you tried to input another source to the LCD or have you tried to connect your pc to another tv??

Yes, he did. Re-read post number 3.

Joe

 

[Modelworks]

Start from the beginning. Try to think of it in terms of how the display works the second you plug it in, then push power, then send it a signal. So the first thing is verify proper power, don't assume because a light is on that all is fine.

Do you have a meter ? Start by locating points on the board that supply voltage to the controller and any other logic parts or memory. They are normally 1.8, 3.0, 3.3, or 5.0 vdc . Once you verify all the parts are getting power locate the eeprom for the controller. That is the first thing the controller is going to try to read when it powers on, no data from eeprom , no picture. Make sure it has power and doesn't have bad solder joints, need a strong light and magnifier. If ok move to the controller, trace the lines from it back to where the signal enters the board.

From the way it failed , if the connection from controller to panel is good I suspect it is power or memory related. Sounds a lot like a controller stuck in a loop. You really need something like an oscilloscope or logic analyzer to diagnose it further.

 

[exdeath]

Yeah, I'm thinking it's the controller. Just to clarify I'm talking about the TFT driver ASIC that connects to the glass itself, not the display processor/EPROM/scaler/etc. The way the image failed (steady working image that gradually faded instead of instant loss)... and the internal OSDs not working either indicate common point of failure after the display processor.

The panel gets warm when it sits, indicating that it's drawing current and working. And the row/column contacts don't fail all or nothing, I'd be getting bars and funny things like that. Given that the display 'boots' and does everything else normal (navigating menus blindly I can adjust the backlight level) I'm leaning on the AUO LCD controller board that sits between the LVD connection to the main board and the ribbon cables to the panel (similar to a keyboard controller in reverse, takes serial stream of image and converts to the rows and columns to refresh the panel). Going to roll the dice and pick one up on ebay.

Haven't had much time to mess with it since, just been using my trusty F500R CRT in the mean time.

Don't have an oscilloscope, but a DSO is high on my shopping list. Trying to find one that's semi portable (battery would be nice) for automotive diagnostics as well. Thinking about one of these. Cheap $400 made in China junk, but if it works, that's all that matters.

 

[dud89]

Maybe you can bake the controller board back to life: http://www.hardforum.com/showthread.php?t=1421792