A31 backlight dying(dead) ?

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pouakai · #1 Post by **pouakai** » Fri Dec 03, 2004 4:01 am

The backlight on my A31 (2652-D5A) is/has failing/ed.
The backlight illuminates with a reddish hue for a few seconds (5-10) after power on then flickers for a second and dies, the display remains barely visible.
I read a couple of other posts which finger either the inverter or the CCFL tubes

The pink coloring seems to indicate the tubes are stuffed but I have some concern about the inverter - I have measured the voltage during power on and this far exceeds 500Vac for the time the backlight is on and then falls to 0V.

Can anyone tell me the approximate operating voltage for the backlight ? ( By my very limited understanding is should be about 180Vac ? )

Alternatively if in fact the backlight tubes are dead/dying is this then the behavior one would expect of a healthy inverter ?

TIA
Chris

friedrich-eugen · #2 Post by **friedrich-eugen** » Sat Dec 04, 2004 6:00 am

Hello,

do look up Your warranty status, if still under warranty it is up to IBm to exchange it...

if not,

do look for a lcd (complete) and/or inverter, but do not try to exchange the backlight yourself. I have come across a manual for doing so by yourself, but I felt extremley unhappy when reading it: it is just hazardous. You probably will not have the tools and/or the talent and/or the confidence needed.

dperron · #3 Post by **dperron** » Sat Dec 04, 2004 9:30 am

Hi,

As Friedrich said, if it's still under warranty don't touch it, send for repair!

I have also had my screen turn pink (on startup only). They first changed the inverter but this didn't fix it. So they had to changed the whole LCD panel (although only the backlight needed to be changed, they always replace the whole panel.) But in your case, you screen also flickers and dies. So that's a big hint that the inverter is the culprit.

As far as i'm concerned, i don't think a healthy would fall to 0v. Obviously it's unable to supply the Backlight... I'm not an expert in backlight and i don't know if the backlight can short out and draw the inverter to 0v (or is it a safety feature of the inverter...). My humble opinion is that your inverter is failing. Change it and then you will see if your backlight is defective also.

pouakai · #4 Post by **pouakai** » Sat Dec 04, 2004 9:36 am

It's well out of warranty, and so figuring I had nothing to lose I have dissambled the LCD and removed the backlight and ordered a new one from 'LCDparts'. While I agree with you that that operation is not for everyone it wasn't too difficult even without instructions, but extreem care is need in order not to damage anything(even more care will be required for reassembly). The backlight in this model is significantly harder to access than that shown in the service manuals for other models of LCD. But hey $10 is WAY better than $400! So I am looking forward to a happy outcome - I'll post back when it's complete.

chris

pouakai · #5 Post by **pouakai** » Sat Dec 04, 2004 4:14 pm

As far the inverter is concerned, I hear what you are saying, but my current theory is that as CCFL grow old they do not go short circuit and draw the inverter output voltage down to 0v but that they approach an _open_ circuit which then allows the output voltage rise too high and trigger the overvoltage shutdown circuit of the inverter........

I let you know after I get the new tubes!

Also if anyone is interested I could post photos of the backlight replacement procedure for the LCD panel?

: )
Chris

dperron · #6 Post by **dperron** » Sun Dec 05, 2004 6:03 pm

Where did you get a backlight for 10$? Who/Where is 'LCDParts'?

Thank!

pouakai · #7 Post by **pouakai** » Mon Dec 06, 2004 11:49 am

http://www.lcdpart.com/

; )

lou146 · #8 Post by **lou146** » Fri Dec 10, 2004 8:35 am

I would be very interested in those pictures.

Have had to get rid of a couple of machines due to this problem and out of warrantee. I would tackle it with some visual help.

Thanks

pouakai · #9 Post by **pouakai** » Sat Jan 15, 2005 4:23 pm

I have finally got around to putting some pictures of the repair operation on a web page for peoples edification:
http://sourcepower.co.nz/A31/A31Backlig ... ement.html

Good Luck!

ian · #10 Post by **ian** » Sat Jan 15, 2005 5:57 pm

I don't own an A31 but I'd like to thank you for your efforts. However it simply confirms what I've thought in the past :- I'll let someone else take my screen apart ! Sterling work - let us know when you next take something to pieces...

friedrich-eugen · #11 Post by **friedrich-eugen** » Sun Jan 16, 2005 12:20 pm

Hello Pouakai,

thanks a lot for the pictures - I find, they show it is quite a job for someone trained to do such fine mechanical/electronics job. I would not dare to do it...

A31 backlight dying(dead) ?

A31 backlight dying(dead) ?

backlight failing

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Repairing a dying lcd-display: quod erat demonstrandum

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