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T430 Backlight dimming = mad flickering

Posted: Sat Dec 08, 2018 1:29 pm
by ketsa
Hello all,

I recently acquired a T430, it works well for my needs but I have one problem with it :

The screen only works correctly on maximum brightness,
One press on Fn-F8, it strongly dims and starts flickering like mad. unusable.
Further presses on Fn-F8 reduce brightness but still flicker very fast.

It is not an operating system issue as it also happens on the BIOS screen, on windows and on Linux.

Any ideas where it comes from ?

Thanks.

Re: T430 Backlight dimming = mad flickering

Posted: Mon Dec 10, 2018 5:47 am
by Screamer
I suspect that it has something to do with the display panel's backlight or the inverter, but have you tried to reduce the flickering via IntelPWMControl?

If the display panel doesn't show any signs of an aging backlight (strong pink/red tint on boot-up), it could be the inverter that is at fault. If I were you, I would replace the inverter and see how it goes from there.

Re: T430 Backlight dimming = mad flickering

Posted: Mon Dec 10, 2018 6:33 am
by RealBlackStuff
T430 does not have an inverter, which was only used with CCFL backlight.
T430 has LED-backlight, which is supported by the LED-board (see HMM pages 108/109).

Re: T430 Backlight dimming = mad flickering

Posted: Mon Dec 10, 2018 11:04 am
by ketsa
Really ? It looks to me like that small led board is only for the wifi and HDD leds.

Re: T430 Backlight dimming = mad flickering

Posted: Mon Dec 10, 2018 12:44 pm
by Screamer
Well, it could be. The panel appears to be solely driven by motherboard's power connector from what the hardware maintenance manual seems to show.

As the inverter's ruled out, I believe the display panel needs to be replaced.
RealBlackStuff wrote:
Mon Dec 10, 2018 6:33 am
T430 does not have an inverter, which was only used with CCFL backlight.
T430 has LED-backlight, which is supported by the LED-board (see HMM pages 108/109).
My bad, sorry. I was under the impression that a LED-backlit display panel still required an inverter to convert DC to AC, but after thinking that through, it does make sense that the inverter would no longer be needed for a LED-backlit panel.

Re: T430 Backlight dimming = mad flickering

Posted: Mon Dec 10, 2018 12:47 pm
by Thinkpad4by3
Screamer wrote:
Mon Dec 10, 2018 12:44 pm
My bad, sorry. I was under the impression that a LED-backlit display panel still required an inverter to convert DC to AC, but after thinking that through, it does make sense that the inverter would no longer be needed for a LED-backlit panel.
Well it does need a driver...but it's a DC driver. The LEDs are driven at like 27-36V constant current...but it's not an inverter because it isn't going DC->AC.

Re: T430 Backlight dimming = mad flickering

Posted: Mon Dec 10, 2018 4:51 pm
by ketsa
I ordered a new LCD panel, we'll see...

Re: T430 Backlight dimming = mad flickering

Posted: Tue Dec 18, 2018 12:51 pm
by ketsa
Received a new screen : backlight dimming works so my screen is definitely defect.

But the screen i received has 2 big light/white streaks... now starting RMA.