T-21 failed backlight? or inverter?

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Bob Collins · #1 Post by **Bob Collins** » Fri Jan 06, 2006 1:32 pm

Okay, short story, the T-21 has full image on the LCD however it is as dim as can be. Obviously the backlight is not illuminating. Could this also be an inverter trouble? Just need some ideas as to what to address.

Thanks much and I know this has been asked a lot, but searching has given me no good results.

Thanks
Bob

PATRICKJEF · #2 Post by **PATRICKJEF** » Fri Jan 06, 2006 1:47 pm

Dark / Flickers / Dim display = Defective inverter board / Lamp

Flickers orange/reddish color = Defective lamp

Bob Collins · #3 Post by **Bob Collins** » Fri Jan 06, 2006 2:49 pm

So most likely I should try the inverter first.
Then the lamp(s)?

Thanks
Bob

LtTPfan · #4 Post by **LtTPfan** » Fri Jan 06, 2006 4:09 pm

Yup, with your symptoms I'd try the inverter first.

Bob Collins · #5 Post by **Bob Collins** » Fri Jan 06, 2006 4:40 pm

Okay great, I'll get on that first. I'll follow up with any relavent info too.

Any suggestions other then the 'bay for this part?

Thank you
Bob

skygodtj · #6 Post by **skygodtj** » Fri Jan 06, 2006 11:51 pm

The 'Bay is prob the quickest, cheapest place for the parts. Look for NEW listings (as in BRAND NEW, not recent)

TJ

Bob Collins · #7 Post by **Bob Collins** » Sat Jan 07, 2006 11:35 am

Fired off on a buy it now listing. We'll see how it goes.

Thanks all!

LtTPfan · #8 Post by **LtTPfan** » Sat Jan 07, 2006 12:14 pm

Good luck! Going by some other threads, it's possibly a mobo problem but they are far less common. I'll keep my fingers crossed for you.

Bob Collins · #9 Post by **Bob Collins** » Sat Jan 07, 2006 9:26 pm

I *think* the mobo is okay, as I can get image on the LCD, just no backlighting at all. I can see all the desktop and taskbar, but it is DIM as can be. Thanks for keeping your fingers crossed, but you can uncross them if you need to type

Cheers
Bob

LtTPfan · #10 Post by **LtTPfan** » Sat Jan 07, 2006 10:18 pm

I'm a onehanded typist most of the time and two fingers at most when using two hands, so I can still keep'm crossed.

There are some threads here where others have replaced or checked everything to do with the screen, i.e. inverter, backlight, LCD, connector, cable, etc. That pretty much leaves their problem of no backlight to the mobo. I believe there is at least a fuse that feeds power to the inverter on the mobo, who knows what else is involved.

Bob Collins · #11 Post by **Bob Collins** » Fri Jan 20, 2006 12:40 pm

Here is the update.

The new inverter did not help. Found a friend who has a T22 and borrowed it's inverter. Also a no-go. So looks to be bulbs or LCD assmebly complete.

Any pointers to bulb replacement, or is that fraught with troubles too.

Otherwise of to the bay to fish out an LCD assembly.

Thanks

Orevin · #12 Post by **Orevin** » Fri Jan 20, 2006 3:59 pm

For bulbs check here:

http://www.lcdpart.com/

It's not too diffcult to change the bulb.

Bob Collins · #13 Post by **Bob Collins** » Fri Jan 20, 2006 4:32 pm

Thanks, I am looking into that right now.

When you say it is not too hard to replace the bulbs, I assume I have to disassemble the LCD frame and remove about 6 or so screws to remove that silver frame that seems to be sandwhiching the LCD and it's other parts? No?

Thanks. Anyone ever take some pics of this operation?

Website · #14 Post by **tfflivemb2** » Fri Jan 20, 2006 5:11 pm

There is some very useful information in the sticky at the top of the 600/770 forum. Granted it is for the 600 series, but I am sure that you can use this as a guide, and yes there are pictures too.

pmurray63 · #15 Post by **pmurray63** » Fri Jan 20, 2006 7:47 pm

I appear to be having the same difficulty as the original poster with my T23. My screen is dark; if I peer very hard at it in bright light, I can barely make out the icons on desktop. (It works fine when connected to an external monitor.)

I'm new to ThinkPads and would appreciate any advice. This thread seems to discuss several possibilities (inverter, bulb, somebody somewhere mentioned a fuse I think); what are they and which should be tried first? How difficult are the repairs? Is there any T2x specific information resource available? Alternatively, any idea what it would cost to have it done professionally? And any recommendations where?

Thanks in advance ...

Bob Collins · #16 Post by **Bob Collins** » Fri Jan 20, 2006 10:54 pm

Upon further review, I put my multimeter on the inverter and found no high voltage. I was getting maybe 12 volts. I was reading that the voltage would be in the 280 or so volts. So, I may indeed have something shot on the mobo.

I have looked the mobo over and cannot find any fuses that look blown. There are two large fuses near the LCD connector, but both look good and have very low resistance.

Now to check the output on the known working T22.

Perhaps I'll update with a pic or two if I find something curious.

#17 Post by **carbon_unit** » Sat Jan 21, 2006 7:34 am

See if your friend with the T22 will let you swap displays to see if your inverter and backlight is good. The whole upper assembly comes off pretty easily.

Bob Collins · #18 Post by **Bob Collins** » Mon Jan 23, 2006 12:00 pm

Was a busy weekend, so I'll be getting to this tonight.

Thanks, was thinking that might be my next action.

AbsoluteRaleigh · #19 Post by **AbsoluteRaleigh** » Wed Jan 25, 2006 10:03 am

Bob Collins wrote:Okay, short story, the T-21 has full image on the LCD however it is as dim as can be. Obviously the backlight is not illuminating. Could this also be an inverter trouble? Just need some ideas as to what to address.

Thanks much and I know this has been asked a lot, but searching has given me no good results.

Thanks
Bob

This is most likely your LCD cable.

If it were the backlight, you would have had warning signs, like flickering or a red display.

Inverters almost NEVER go bad in T21s. (Maybe 1/5000 chance).

Bob Collins · #20 Post by **Bob Collins** » Wed Jan 25, 2006 10:34 am

Last night I got to check the T22 versus the failed T21. The T21 puts out maybe 12 volts from the inverter, the T22 put out over 200 volts until I saw a spark shoot across my test leads and dea was the inverter. Good thing I had a spare!

Okay, AbsoluteRaleigh, now I have to pull the T22 LCD assembly and put it on the T21 frame to see if the cable is bad, no?

I'll do that tonight. Yippeee.

madmaven711 · #21 Post by **madmaven711** » Mon Jan 30, 2006 10:20 pm

Hi, I have a similar problem. the T21 display is very dim but you can just see the full windows, desktop icons, etc . When I press the Fn and F7 for dual display twice the screeen comes back for about 3 seconds then goes dark. I can repeat this over and over and the display always comes back for a couple of seconds. . Do you think this is more likely the inverter board? Any ideas would be helpful As this is a pretty big job for me .

Thanks Madmaven

LtTPfan · #22 Post by **LtTPfan** » Mon Jan 30, 2006 11:35 pm

madmaven711, your symptoms sound like the inverter.

Bob Collins · #23 Post by **Bob Collins** » Tue Jan 31, 2006 8:49 am

Okay no resolution yet. Too many other projects jumping in the way. Gonna send it off to someone who has better equipment for testing such things. Once I have some more info I'll post.

Thank you to all who offered guidance and helpful pointers.

madmaven711 · #24 Post by **madmaven711** » Tue Jan 31, 2006 5:29 pm

Hi,
I have ordered the inverter from the bay as you affectionately call it and will attempt the disassembly as soon as it comes in.

Cant beat the price 2 for $15 includes shipping and they are guranteed not DOA.
I'll keep you posted as to the outcome.
Thanks for the advice.
Madmaven

pjm99au · #25 Post by **pjm99au** » Tue Feb 07, 2006 8:19 am

I had very similar problems with the display of my R40 (backlight not working, could just see the IBM logo and windows logo on startup if you looked closely but none of the other warning signs such as red tinges etc). After disassembling and checking the inverter and the LCD cable a few times I discovered that the problem was with the small switch which is closed when the screen is closed. The switch activates hibernation (when that option is selected) and turns off the screen backlight but maintains the signal to the screen when it is not.

The switch spring works fine so it took a while to identify the problem but a bit of "digging" with a small screw driver levering the switch up (with the notebook on) resulted in the backlight coming back to life. I then trimmed the "lug" on the screen down so that it wouldn't push on the switch when closed. Can't say this is your problem but would highly recommend anyone with a dim / no backlight display to try levering up the microswitch

Regards

Peter

Bob Collins · #26 Post by **Bob Collins** » Tue Feb 07, 2006 9:55 am

pjm99au,

Thanks for a great suggestion. I'll try that on the T-21.

madmaven711 · #27 Post by **madmaven711** » Tue Feb 07, 2006 11:59 pm

I changed the inverter and tried both of them, and the light is just the same. flashes for a few seconds then dies. I then procured a cable and changed it and the same problem. I will check the close display tab tomorrow and make sure it isnt sticking like you said but I think not. I have just bought a dsiplay on the bay and when it travels at snails pace from CA to Fl I will try that. some day this machine will be fixed!!!

T-21 failed backlight? or inverter?

T-21 failed backlight? or inverter?

Re: T-21 failed backlight? or inverter?

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