Possible free solution to fix T2x Backlight problem

[Matt123]

Hello, I thought I'll post my solution to fix the backlight problem on my sisters Thinkpad T21. Because I've read though this forum before for other problem, which have helped me. And I'll add my little bit...

The problem originally appeared to be a inverter problem (FRU 10L1402). Because 3.3v and 16v were getting to the inverter, but there was no high frequency coming out?, after buying a inverter from ebay - it did not help.

After playing around and blowing Fuse 4 (which totally knocked out my display!). My Thinkpad 600 (Pentium II) had the same inverter connector with 1 extra 3v line.

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T21 Pin layout from the cable side
----------------
|  1       7   |
|  ---------   |
|  \_______/   |
|  8      14   |
----------------
it maybe incorrect pin numbering?, but its no big deal. As long as it makes sense

1 - 3v . (180ohm to Gnd) . (5v on TP 600)
2 - NC
3 - Originally appeared as NC . (3v on TP 600)
9 - 3v . (180ohm to Gnd) . (NC? on TP 600)
10 - NC . (5v on TP 600)
4,5,8,11,12 - Gnd
6,7,13,14 - ~10v to ~16v . (Brightness)


Temporarily Shorting pin 1 or 9 to pin 3, activated the backlight. But I did not want to buy a new cable (FRU 27L0519) because it was not worth it.
So I added a small smd high resistor on the inverter. I luckily found a 100K but a short circuit should work as well. The picture shows where I added it.
. http://img294.imageshack.us/img294/3006 ... esisto.jpg

If one of the Pins 1, 3 or 9 are Not Connected / Open Circuit. You should be able to connect it to another pin. It might save you £15?
There does not appear to be any side-effects?. However I think that Pin 3 was designed to be a screen blanking pin. When it switches between different resolutions.
P.S. T4x models have a different connector.


This is just a guess here but....
If you screen is not getting the 3.3v supply because of a broken cable. Maybe taking the supply from Pins 1 and 9 of the inverter... Add a wire up-along the back of the screen onto the first 2 pins of the screen. LCD Pins 1+2 are 3.3v. LCD Pins 3+4 are Ground.
Or it might blow a fuse?


Good Luck & I hope it helps...
Matt