T42p activity LEDs not working

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iraqigeek · #1 Post by **iraqigeek** » Wed Oct 01, 2008 4:48 pm

Hi all,

I have a new (to me) t42p (15"). The laptop works fine apart from one thing, none of the activity LEDs under the LCD panel work (hard disk activity, caps lock, num lock, bluetooth, wifi, power, etc)???

Is it a problem with the LCD inverter (I'm assuming the leds are on the same board as the inverter)?? I have an LCD inverter from my dead T40p (14.1"), can I use that inverter istead???

#2 Post by **Harryc** » Wed Oct 01, 2008 5:22 pm

They use different inverter cards. 14" = 26P8464. 15" = 93P4161. I am guessing they are not compatible.

iraqigeek · #3 Post by **iraqigeek** » Wed Oct 01, 2008 7:11 pm

Harryc wrote:They use different inverter cards. 14" = 26P8464. 15" = 93P4161. I am guessing they are not compatible.

I know, I checked the part numbers, and they are a bit different. But both have the same connectors at about the same locations. My intention is to test to check whether its a problem with the inverter board or whether its a problem with the ribbon connecting the LCD to the motherboard.

sjthinkpader · #4 Post by **sjthinkpader** » Wed Oct 01, 2008 7:25 pm

Check fuses F7 and F8 too. They are located near the LCD connector on the MB. Here is a related post:

http://forum.thinkpads.com/viewtopic.ph ... t=fuse+map

iraqigeek · #5 Post by **iraqigeek** » Wed Oct 01, 2008 8:45 pm

sjthinkpader wrote:Check fuses F7 and F8 too. They are located near the LCD connector on the MB. Here is a related post:

http://forum.thinkpads.com/viewtopic.ph ... t=fuse+map

Thanks, I'll check the fuses tomorrow morning. I tried using the inverter from my old T40p just to see if the LEDs will light up, and while it worked the LEDs still wouldn't light up. The only ones that I got working after re-installing drivers were the bluetooth and WiFi LEDs. But all the others are dead. I also tried using the LCD from my T40p with the same result.

Another strange thing I'm having is that there is no sound in Windows XP despite the sound card showing as working properly in the device manager. I can hear the beeps clearly when I connect and disconnect the power cord, but nothing in windows. Guess I'll leave that for another thread after I check the fuses.

iraqigeek · #6 Post by **iraqigeek** » Thu Oct 02, 2008 2:33 pm

sjthinkpader wrote:Check fuses F7 and F8 too. They are located near the LCD connector on the MB. Here is a related post:

http://forum.thinkpads.com/viewtopic.ph ... t=fuse+map

I tried replacing both the inverter board and LCD panel, and nothing but the wireless and bluetooth LEDs worked. However, I tried plugging the 15" LCD and its inverter board on my dead T40p and they do blink on POST, so there's nothing wrong with the LCD ribbon or inverter board.

I guess that leaves only fuse F8???

#7 Post by **richk** » Thu Oct 02, 2008 8:35 pm

Most of the times I've seen that sort of problem, it is in the motherboard. My suggestion is to decide "it's not thab big of a deal"

iraqigeek · #8 Post by **iraqigeek** » Fri Oct 03, 2008 4:13 pm

I changed fuse F8 and now all the status LEDs are working fine.

Thanks for all the help guys

sjthinkpader · #9 Post by **sjthinkpader** » Mon Oct 06, 2008 5:51 pm

Good for you and thanks for posting a definitive feedback.

xyz · #10 Post by **xyz** » Wed Oct 08, 2008 6:24 pm

Just had this on 2 machines, replaced F8 and they are working fine

T42p activity LEDs not working

T42p activity LEDs not working

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