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Thinkpad T20 inverter putting out under 1 volt on high voltage side, ideas thoughts ?

post #1 of 7
1/12/06 at 10:29pm
Thread Starter 
Ok first off lemme say thakns to whom ever is hosting and running these forums..

next let me say in and

I have a Ibm thinkpad T20 2647-44U.

I was doing a network job for a freind of a freind,
they mentioned they had the laptop and the backlight quit on it.
I figured I would do the network job as a freebie and buy the laptop
from them.

They described the symptoms as they were using it,
put it away and did what ever they do.
The net time they tried to power up the laptop they said there
was no light to the screen.

upon checking it out I figured it looked like a common problem
with other thinkpads and laptops. A simple backlight inverter failure.

As of now I had bought 512 ram for the laptop, DVD reader Cd rw combo drive, a 30 GIG HDD, and 2 Inverters.

I got the inverters in FINALLY!!.. And take the screen bezel off and
replace the inverter. Verified all connections and everything seemd ok and
in place.. I figured while I have the bezel off I should test this to make sure
That were lit up and can put it back together..

STILL NO BACKLIGHT!!!!!

I got the Ibm maint manual took a look at it and followed the suggested
steps they say and verify screen connections and all points where the video
cable connects to (which also has the inverter power IN connections).

Cable looks good, everything seemd in check even reseated connections.
I still have NO highvoltage coming out of the inverter,
From what I have read I should detect a spike of aprox 750 volts to start the bulb and aprox 500ish to maintain the light..

When testing the leads off the inverter im getting .6 yes POINT SIX volts!!

Sooooooo has anyone else had this problem I am reading auctions about on ebay now??....

Backlight failures due to no power to the inverter???
(I am assuming this is no power to the inverter due to no voltage out from the inverter I just opened which was tested by a reputable company on ebay)


specs
PIII 800 or 700 dont remember off hand.

14" Xga tft
nothing non standard.
running all testing etc WITHOUT hard drive and dvd roms in place..

Are there board level fuses???

please anyone and Everyone if you have delt with this or know anyone who has I really would aprecate input from anyone!!


P.S. If you know someone who dosent read here but may know a fix please forward this message on to them or to other forums...

Reallllllly would like to know i didnt waste $$ buying this laptop and one for my g/f with the same apparent problem!!
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post #2 of 7
3/9/06 at 2:51am
Did you buy a 512mb stick of ram or 2 sticks of 256?
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post #3 of 7
4/3/06 at 6:19pm
Interesting enough, I think I'm having similar problem on my T20 machine.
I also bought an inverter to try my luck, but no luck on it.

Below is the description on my problem that I posted on other forum.

Quote:
I've an IBM T20 Thinkpad. It's about 4-5 years old.

The last 2 years, I been having problem with the LCD screen. It will get dimmed all of the sudden or dimmed when I first boot the machine. But I'm able to regain the color after folding up or hitting the lcd screen softly.

Finally, the last couple of days, the trick that I mentioned no longer work.

I did a little research, and I see there're 3 possible things that I could look into.
1. Invertor
2. Backlight bulb
3. LCD cable (cable connects from the lcd to the motherboard)

I'm not sure which part I should get, because I don't know which part is not working. I'm just wondering base on the scenario I provided, is there anyone know or take a good guess which part went wrong?
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post #4 of 7
4/21/06 at 3:13am

Same Issue t21

i have a t21 that i got as salavage
after reflashinf the eeprom to remove the super password buying a power supply anf a hdd cause the current one had a hdd password. i loaded windowed and load the backlight the how time the back light was acting up sometimes working sometimes not working and normaly closing the screen hlfway and opening it would getit to work.
but it will not do that any longer i tryed to test the bulb with a blacklight inverter in my PC but i broke the bulb on removing it( thou i had a Old laptop i was abl yo salavge the light from which when hooked to my black light inverter works and is super bright) so i wired it to the thinkpads inverter and nothing i then orderd a new inverter and still no light.
Any ideas would Great be welcomed
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post #5 of 7
5/13/06 at 12:27pm
Hi,
I had exactly the same problem with my TP 770x.
Changed the inverter: no permanent result - it worked some time,
then again blinking, and blackout.
-> Output to external monitor is ok.

Here my thoughts:
It must be a problem with the voltage - overheating?
So I disconnected everything: battery, AC adapter
and let them COOL down for 2 hours.
Dimmed the backlit.
Boot again - and voila: it works.

I booted into DOS and started the ThinkPad utility PS2.exe.
Here I set everything to DEFAULT - and LCD to "no timeout" =
ps2 LCD 00 ac.

This worked (for now), my TP 770 is up again.

So this seems to be a complex thermal problem
which envolves several parts of the Thinkpad :
AC adapter (external),
DCDC board (interal),
DCDC inverter (LCD).

Hope this helps for you too.
Yours Peter
(from Germany).
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post #6 of 7
5/20/06 at 3:34pm

IBM thinkpad Back light Problem

Ass above my T21 has a backlight issue i replaced the Light (when removing the fist light to test it i snaped the bulb OPPS).
Instlled new light still nothing replaced the inverter boad again nothing ( i had given the inveeter board 50% liklyhood to be the issue due to ease of fix and cost). Though with out a second Laptop to confirm the board is bad the second inverter could be bad(GO EBAY! ) I know the Bulb works and ithat it is lined up correctly cause i bought a Light for my PC and Hooked the inverted from my PC to my lapto and scren works fine. So im not a big fan of a bad cablethou it is possable Idea any other ideas would be greatly appreciated.
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post #7 of 7
5/25/06 at 10:36pm

same problem with G40

I Have the exact same issue with my thinkpad G40. one day, screen dimmed, so thought it was a backlight... $90US lighter later, i have a new backlight, but broke it trying to put it in!

so, opted for a new screen with a backlight already in it... all the places i went wanted $500US for the screen, i only paid $300 for the laptop off ebay!

so i got me a screen off ebay for a thinkpad R40, after assurances from the seller it was compatible with my G40... $143AUD later, i get my R40 screen and find its NOT compatible with my screen!

so, anyways, i figured i could take out the lcd panel from my screen and place it into the LCD Panel on the R40 screen and therefore have a working backlight (As assured by this ebay seller) so that went smoothly, put the panel into the g40, hooked it all up, nothing!

one or twenty emails later to the ebay seller accusing him of robbery, scamming and every other insult i could think of, got me nowhere... except a word from this seller to tell me that if i could shine a torch on the screen and see the icons, then it was the inverter, not the backlight...

this appeared to be reiterated on the forums i was on... so again, $90AUD to another ebay seller in the US, i get me an inverter for my G40. it arrived today, so i switch it for my old one, hook everything up, turn it on, and..... NOTHING!!! Same thing!!

now im pissed!

i've spent more on this issue than the whole laptop altogether!

im no closer to finding out what this could be and reading this thread, it appears its a common problem across the thinkpad range...

an email to IBM support resulted in a response asking for $ before they will answer my question... my warranty expired 9/2004

I wonder if IBM are aware of this issue? most likely, but i dont see anything on their website about it....

its frustrating to say the least!!!
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