Laptop screen issues

[Buyasta]

LCD panels do not use VGA signal. it's different and proprietary. (and a pain in the a55)

But if it is the same chip supplying the (still working) VGA as well as the panel signals, it suggests one of the chips on the panel is damaged, and not a graphics card problem.

Yup, exactly - there's not going to be any additional circuitry for the LCD output like there will for the VGA, to convert from a digital signal to an analogue one. So if it were the VGA out that wasn't working, then it could be an issue with the graphics hardware, but since it's the LCD that's the issue, that seems pretty unlikely.

[ducatilover]

Something's broken mate

You're welcome.

[5150]

My laptop screen started having issues last night, and appear to go into a test pattern, with solid green/blue/red followed by black/white and some gradients in between. While it is doing this the VGA output is fine, and the compute boots and shuts down as normal. Unfortunately I changed some settings awhile ago to get desktop 'span' going, so I can't get anything up on the vga output/screen. I took it all to bits last night, but couldn't see any connector problems.
My thinking is, VGA is working so the display board might still be good, screen test pattern is working, so screen might still be good.
Laptop is a G51VX (bestbuy).
During startup and shutdown the screen will flicker to what it is supposed to display, though this image is often interlaced with black lines, or only fills the top half.

So whatcha reckon? Screen? Cable? Display Board?

Oh FFS, stop looking at all that porn

[bogan]

Kept using it cos I'm pretty cheap, and wanted to be sure of the problem. I also noticed it would drain the battery even when turned off, so I thought maybe something else was wrong, but I disconnected the panel and it stopped draining the battery too, so another point in favour of a new panel.
Seems a bit strange that a bung panel could drain the battery though, figured it would have all been turned off 'upstream'.

[ducatilover]

See, I told you something was broken.

[Buyasta]

Kept using it cos I'm pretty cheap, and wanted to be sure of the problem. I also noticed it would drain the battery even when turned off, so I thought maybe something else was wrong, but I disconnected the panel and it stopped draining the battery too, so another point in favour of a new panel.
Seems a bit strange that a bung panel could drain the battery though, figured it would have all been turned off 'upstream'.

That is quite stupid, you'd think the laptop would cut power to the screen when it's turned off.

[bogan]

Irritating problem still persists. Got a new panel, have not had any of the block color 'test patterns', but the LED backlight often goes out, or the screen goes completely (thought this may just be lack of backlight not allowing me to see the pixels). Anyway, when I unplug and plug back in the cable connecting to the panel, it often comes right, and is fine to close/open lid or move it around while it is going. however, when I turn the computer off, and on again, it often doesn't fire the panel up. So I'm thinking it is more than a connection issue, maybe the panel power is left on, and causes the driver chips on the panel to go into a sleep mode, since there is already power turning the computer on doesn't wake it up, but un-plugging the cable does. Anybody else got any theories?

[bogan]

Ok, just did a restarts, screen worked but no backlight. Unplugged and re-plugged the other end of the connector and it came right again. Something fishy with the LED backlight controller perhaps. Will try it a few more times during the course of normal useage, and maybe just put in a little button to reset the backlight as needed.

[pete376403]

LED backlights or cold cathode flourescent? If CCF - could be a problem with the inverter. Does the screen have a small (about 100mm long x 10-15mm wide) board, usually found at the bottom of the display.
Inverter supplies the high voltage for the CCF to illuminate.
http://www.laptopscreen.com/English/...ur+new+screen/

[bogan]

LEDs, though I'm fairly sure these run an inverter too, but only a 20V or so one.

[bogan]

Narrowed a fix down to reseting the enable pin for the panel LEDs; the inverter is on the RHS screen plug so no too hard to get access to. Interestingly, the first panel had no problems with the backlight; so as far a fault diagnosis goes But as far as kludging it to a workable state goes Just put a microswitch on that signal wire, and give it a tap every time the laptop has finished booting, or the panel needs a wakeup. Few days in, and no problems so far...