NEC NL10276BC20-04 LCD all white when no signal

[perdrix]

So I replaced an NEC NL8060BC26-28 (800*600) with an NL10276BC20-04 (1024*768).  All works perfectly with one strange exception.

When there is no signal (immediately on power up before BIOS display, various times during Windows boot, when Windows turns off the screen) the screen goes all white rather than all black.

Any ideas?

Thanks
David

[Phaseseeker]

The old panel (the 800x600 one) supports both 8-bit and 6-bit color modes, selectable with a pin, whereas the new one only supports 6-bit color. Since changing from one mode to another changes the order of the bits in the LVDS lines (and also which lanes carry which signals) maybe the display is getting the data in the wrong order making it do funky stuff.
Also, unrelated to the problem, did you just plug the new display in place of the old one and it worked or did you have to do something to adapt it? Because I'm looking to do something similar on a laptop I own and I'm not sure if I can just swap in a higher resolution LCD and expect it to work

[perdrix]

Pin 4 is low - I remember checking the pins that controlled behaviour  - maybe it needs to be NC?

Other than this issue it was a straight swap apart from changing the connector housing for the backlight from a 3 pin one to a 4 pin.

David

[Phaseseeker]

It's worth a try to disconnect at least pin 4 (since it's specifically stated that's NC) but it's not exactly what I was referring to. If you check pages 17 and 18 of the NL8060BC26-28 datasheet (https://datasheetspdf.com/pdf-file/625212/NEC/NL8060BC26-28/1), there's a diagram that shows the way the RGB and sync data is transferred over the three LVDC differential pairs in the three different "maps" the display supports. The NL10276BC20-04 (https://datasheetspdf.com/pdf-file/847133/NEC/NL10276BC20-04/1) datasheet does not show explicitly the order of the data bits, but if you look on page 14 it shows the LVDS trasmitter wires, and if you look at the three diagrams on pages 14, 15 and 16 on the 800x600 display you'll se that in some of the modes the way the transmitter is configured (and so the bit order) is different, so maybe it's getting the wrong data. It seems weird that it would only cause problems when the screen is blank, but that's the only difference between the two displays I could find that might cause problems

[perdrix]

Well pin 4 is now NC.  That made no difference.  White screen but only when no signal.

I can live with that.

[nctnico]

Some TFT screens show this behaviour. In order to mask this behaviour you can try to disable the backlight inverter when there is no valid signal.