Lenovo Thinkpad T400 Issue

[Matt_Raj]

Hi guys,

I have a thinkpad t400, and am facing the following issue.

When I turn it on, I can see a faint Thinkpad logo appear. After that, nothing. i connect it to my external monitor, and it works as a desktop. Everything but the display is fine. At least I think so.

Furthermore, I replaced the LCD ribbon cable. After that, it worked normally for a while, with the display working as expected. Suddenly one day, it went back to the old problematic mode.
I'm pretty sure I'm not alone here, but NOBODY should want to keep buying ribbon cables.

Kindly make some suggestions.
Thanks Guys!
-matt

 

[ffg7]

I don't think it is a cable issue but a screen issue. have you reseated both ends of the videocable?

 

[Matt_Raj]

I don't think it is a cable issue but a screen issue. have you reseated both ends of the videocable?

Oh by both ends, if you mean the one that plugs into the display and the motherboard, no.
Damn, that's a good point. I'll try that. I properly reseated (recently) the motherboard side of the cable.

By the way, my hinge is loose - could this have an impact on the display cable? (Like the display wobbles quite a bit if you tap it)

Thanks for your help!

 

[ffg7]

yes as cable can be damaged. check the cable where it passes the hinge for any damage. anytime I work on a customer's laptop, I tighten all the bottom screws as they get loose over time.

 

[Matt_Raj]

yes as cable can be damaged. check the cable where it passes the hinge for any damage. anytime I work on a customer's laptop, I tighten all the bottom screws as they get loose over time.

I checked the cable routing and it seems smooth. There are NO abrupt bends or stresses on the cable.

By the way, the cable powers the following:

1. Webcam
2. Thinklight (Thinkpads have the Thinklight (a keyboard light) powered by the display cable.)
3. Microphone
4. Bluetooth/Wifi Card at the bottom left beneath screen
5. Status lights
6. Screen

When I tested whether the cable has an issue by turning the think light on and off, I concluded that the cable was fine. The light worked as expected.

However, I note the following behavior. The status lights at the bottom of the display don't work, except for the Wi-Fi light. There should be a hard drive light that blinks, a power light that should be on, and a battery charging light too. But none of these light up, as they used to. I reseated the cables for items 4 & 5 from the list above, just to be sure. Nothing changed, only the wifi light works.

I also noticed that there are a couple of black wires that are routed through the laptop's hinge. What do these cables do? Haven't touched them. My guess is that they are the wifi antenna's cables, but am not so sure.

This may be irrelevant, but I've noted this behavior for perhaps the third time. I have 2 sticks of DDR3 4GB RAM, totaling to 8GB. For some odd reason, if I swap the sticks between the two slots, the computer doesn't recognize them (beep code: 1-3-3-1) it only works when they are in specific slots. Furthermore, when I boot the machine and hook it up to an external display, under the about this PC section, it says 8GB RAM (2.46GB usable) why is this?

Kindly let me know of any further suggestions.

Thanks!
Matt

 

[ffg7]

the 2 black wires are the wifi antenna as they go up both sides of screen but do not meet at the top.
are the ram made by the same manufacturer?
max 4gigs of ram. https://support.lenovo.com/ca/en/solutions/pd005598

 

[Matt_Raj]

the 2 black wires are the wifi antenna as they go up both sides of screen but do not meet at the top.
are the ram made by the same manufacturer?
max 4gigs of ram. https://support.lenovo.com/ca/en/solutions/pd005598

Thats odd, I've seen numerous accounts of users successfully using 8GB ram. And yes, they are both by Transcend.

With the display, is there anything else that you would recommend I try?

 

[Matt_Raj]

the 2 black wires are the wifi antenna as they go up both sides of screen but do not meet at the top.
are the ram made by the same manufacturer?
max 4gigs of ram. https://support.lenovo.com/ca/en/solutions/pd005598

On the off chance, could this be a software issue? I mean, I can see "ThinkPad" very faintly on boot. Maybe it's stuck on low brightness or something? I can't adjust brightness with the key combo tho

 

[ffg7]

what is the full model# of the laptop as in Thinkpad T400-xxxx to see if led or cathode backlight? do you have access to an ohm meter or multi-meter even a friends?

 

[Matt_Raj]

what is the full model# of the laptop as in Thinkpad T400-xxxx to see if led or cathode backlight? do you have access to an ohm meter or multi-meter even a friends?

T400-2765 1440 x 900 Display. And yes, I have a multimeter with me with those capabilities.

Thank You!

 

[ffg7]

it is a 30 pin CCFL screen not led screen. https://www.laptopscreen.com/English/model/Lenovo/THINKPAD%20T400%20SERIES/
is there a narrow circuit board about 3" long with 2 3 or 4 pin connectors on it with 1 going to the screen itself?

 

[Matt_Raj]

it is a 30 pin CCFL screen not led screen. https://www.laptopscreen.com/English/model/Lenovo/THINKPAD%20T400%20SERIES/
is there a narrow circuit board about 3" long with 2 3 or 4 pin connectors on it with 1 going to the screen itself?

I believe what you're talking about is called an inverter (looked it up online, as I was wondering if it could be a problem).

There are 4 components served by the cable:

1. Webcam/Thinklight
2. Display
3. Bluetooth Card
4. Inverter and Status Lights

It sits right below the display, and is served by one connector (kinda looks like the type they use for the keyboard, not sure how many pins, there are many). Wait a minute, I went to the website you linked and it looks like there is a separate "Backlight Cable" part of the display. As far as my memory goes, I believe that the only connection given to the LCD is the display connector, NOT the backlight. I guess that could be it. But then again, the status lights don't all work either.

Thanks!
-Matt

 

[ffg7]

where the lights working before you replaced the lcd cable?

 

[Matt_Raj]

where the lights working before you replaced the lcd cable?

Good point. This was a while ago, but the lights were working fine, until the weeks leading up to the disaster. For example, I noticed that the laptop would go to sleep when I raised the display (when it was supposed to awaken), and vice-versa. I know that after replacing the cable, the lights did not work (except the wifi activity light, which still works 'cause it blinks intermittently kind of like a hard drive activity light)

Thanks!
-Matt

 

[hang-the-9]

You should be able to buy a working T400 for maybe $100 and swap your drive into it. Easier than buying parts or a new screen.

 

[Matt_Raj]

hang-9 thanks, but I feel uncomfortable doing that, as my motive was to preserve this machine as sort of a legacy one. Thus the hopes of restoring it back. Perhaps I will replace the inverter board.

 

[hang-the-9]

hang-9 thanks, but I feel uncomfortable doing that, as my motive was to preserve this machine as sort of a legacy one. Thus the hopes of restoring it back. Perhaps I will replace the inverter board.

Inverter is cheap, I think last few I got were about $10 or so.

Just keep in mind before you go into buying screens that a T400 can be found cheaply in many places and if you swap your drive into it, it will be like yours with no issues. You may get an activation error from Windows at some point due to different serial numbers but that is easily fixed by reactivating.