W701 RGB LED backlit display: momentary all green

[Tableteer]

Hardware particulars: W701ds, WUXGA (1920x1200) RGB LED backlit main display.

Summary: There is a lag when all red, green and blue LEDs are turned on. Usually, green LEDs lead, others lag. In other words, individual LED color types turn on sequentially rather than concurrently.

When the monitor is turned on, it is usually momentarily green. You can see objects on the screen but everything is green - visualize it as a monochrome green graphical user interface. Then the proper color is displayed obviously because the red and blue LEDs become activated. One rare occasions, it is red for about a second meaning the red LEDs come on before the others. It has never displayed blue in such a manner.

The entire screen is the same monochrome color. That is, if it's green for a second, it's consistently green throughout. There are no isolated "patches".

It occurs when the computer comes out of idle, standby or sleep where the monitor had turned off. It does so at a frequency of about half the time.

Anyone else experience this? Is it "normal"?

[Harryc]

Does this occur on an externally attached monitor?

[Tableteer]

It occurs ONLY on the main display, not the attached slide out display (it has CCFL backlight), not any number of external monitors that were attached via VGA, DisplayPort and DVI.

I favor the theory that it has something to do with the separate red, blue and green LEDs used for for backlighting and/or control circuitry. Of course, alternate theories are welcome to help explain this phenomenon.

Again, it should be pointed out that it occurs when the main monitor re-activated upon the computer coming out of idle, standby or sleep. It does NOT occur randomly while operating the computer.

[Harryc]

My guess is that the LCD panel or cable are defective. The only caveat there is you need to swap them to prove it one way or the other. Call Lenovo for service if it is under warranty.

[Neil]

the theory that it has something to do with the separate red, blue and green LEDs used for for backlighting and/or control circuitry.

Seems your theory is based on a very common misconception of how LED backlight works in LCD displays. To set the record straight, it is important to note that the LED designation refers to the backlight system used in many newer LCD displays, not the chips that produce the image content.

LCD chips and pixels do not produce their own light. In order for an LCD display to produce a visible image on the screen the LCD's pixels have to be "backlit". And, as far as I know all laptop displays use a row of LED's to light the panel from the edge just like a CCFL does. So the LED array only produces a blueish white light, the color is produced by the LED panel itself.

The other type of LED backlighting is referred to as Full-Array (also referred to sometimes as Full LED). In this method, several rows of LEDs are placed behind the entire surface of the screen. The advantage is that these sets can employ "local dimming". Local dimming means that each LED or a specific group of LEDs can be turned on and off independently within certain areas of the screen, thus providing more control of the brightness and darkness for each those areas, depending on the source material being displayed. On the other hand, LCD displays that employ full array or full LED backlighting are thicker than LCD's that employ an Edge-lit LED light source. Thus my thinking that no laptop displays use this kind of backlight. But, even with Full-Array lighting, it's still the LCD and not the LED's that produce the colors.

[xiphmont]

Thinkpadder is unfortunately completely incorrect. The W701 is not using a white backlight, and it is not spacing the LEDs out uniformly behind the screen.

The W701 uses a bottom-edge lit RGB LED backlight with red, green and blue LEDs that are regulated separately. The whitepoint can thus be adjusted completely independently of the LCD LUT. The 'turn on green' (or some other color) habit is indeed the backlight and not the LCD itself.

Take one apart, you'll see the construction clearly.

[edit: Oh, and yes, mine occasionally comes up some solid color before becoming white. I assume it's due to the regulator being powered up in an uninitialized state that the BIOS is not restoring until a few seconds into repost]