[ltp] T61 screen flickering (backlight tube)

[tomtom at tutanota.com]

Dear Keith, Chris, Stefan, Hendrik-Jan and everyone else!

I've been very busy lately and didn't find the time to reply to your answers so far. Thank you for your help with analyzing my problem and suggesting possible solutions!

So, now at least I'm sure it has nothing to do with the GPU, and that it's a problem of the backlight.

I love Keith's suggestion to "hack" the screen with a LED backlight, but honestly right now, I can't imagine when I would have the free time for such a project. If I found one, my preferred option would be to replace the screen as a whole. But I didn't find a 14.1" 4 by 3 screen yet (or a whole T61 of that size where maybe something else is broken), so I'll have to to exchange the backlight separately.

I found one which I hope will fit:
https://www.ebay.de/itm/233002573330?hash=item3640091e12:g:~0wAAOSw8PJb6T0E

Thanks again for your answers! I really appreciate this list and the effort people put into helping each other out!

All the best,
Tom








29. Apr. 2021, 06:56 von keithl at kl-ic.com:

> On Wed, Apr 28, 2021 at 11:20:14AM +0200, Hendrik-Jan Heins wrote:
>
>> Apperently in these it is related to broken capacitors in the power
>> supply for the backlight.
>>
>
> On Tue, 27 Apr 2021 21:01:32 +0200 (CEST) tomtom at tutanota.com wrote:
>
>> with turned up brightness. Also, sometimes areas that should for
>> example be white turn a bit pinkish or even orange, mostly just for a
>>
>
> I sent a more extensive writeup and suggestions to tomtom,
> but the
> "areas turn pinkish or even orange"
> is the Big Clue - that means the backlight tubes are
> producing colored rather than white light,
>
> The pixel array is probably not responsible, and the power
> supply can't change the /color/ of the light.
>
> My wild guess is that tomtom's backlight is a fluorescent
> lamp (or lamps top and bottom?), resembling the ancient
> tube lamps over my office desk.  However, unlike those big
> overhead lamps, the volume of the spagetti-thin backlight
> tubes is tiny, and the "end seal to volume ratio" of
> backlight tube is enormous.
>
> The mechanical stresses on the backlight ends are much
> higher --- imagine shaking your office (scaled) the way
> you shake your laptop and screen.
>
> So in time, I would expect those backlight end seals to
> leak a wee bit of air into a much "wee-er" backlight tube
> internal volume.  That will add the light emission lines
> of oxygen and nitrogen (yellow and red?) to the mercury
> vapor UV emission lines (which excites the phosphor).
>
> The extra emission will also increase the current draw
> of the backlight tube (it is discharging both mercury
> atoms and the air atoms), electrically stressing the
> inverter that drives it.  So that will go soon as well.
>
> That is a very elaborate wild guess. 
>
> Bottom line - replace the tubes, maybe the inverters too.
>
> I suggested tomtom look for an archive of Xiphont's LED
> replacement kit from many years past.  tomtom (or one of
> you) should consider spearheading an effort to make some
> replacement LED strips and sell them (with instructions
> to the rest of us.  More brightness, more efficiency, no
> leaky glass tube, no high voltage inverter.
>
> I'd gladly buy a dozen kits at semi-reasonable price; $200?
>
> I hope to keep using my 4x3 T60s and X61s for a few more
> decades, replacing ancient components (including the
> motherboard? The batteries and connectors?) with new
> tech as it becomes available. 
>
> A future of chicklet-key runt-screen throwaways and
> electronic toxic waste may be content-consumer utopia
> for some, but it is my idea of hell.
>
> Keith
>
> P.S.  As my office fluorescent tubes fail, I replace those
> with LED tubes as well.  Three times the out-of-pocket
> cost, but I expect the LED tubes to last three times
> longer, and not generate toxic waste at end-of-life.  Also,
> fewer toxic consequences when the next Cascadia Subduction
> Zone earthquake happens (very seldom, but guesstimated
> Richter 9.5).  40 fluorescent tubes breaking and spilling
> their mercury will turn my damaged office into a superfund
> site.
>
> -- 
> Keith Lofstrom          keithl at keithl.com
> -- 
> The linux-thinkpad mailing list home page is at:
> http://mailman.linux-thinkpad.org/mailman/listinfo/linux-thinkpad
>

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