Thinkpads Forum

I renewed the screen front bezel on my Lenovo T400 laptop a few days ago. It was working fine before I started but won't power on at all after the new bezel fitted. The power button is on the keyboard. Followed all suggestions on the forums and Youtubes but no joy.

Although changing the bezel didn't involve any connections other than removing the battery, just screws and clips, I tried all the following:

Power reset. Disconnected power cable and battery, held down power button for 1 min ( or 10 secs repeatedly. then reconnect and power on. Repeated several times.

Tried power lead only, no battery.

Swapped power leads.

Checked voltage (20V) at the power lead connector.

Checked power lead fires up my other laptop.

Tried on a docking station, (the dock lights up when laptop docked) and used the dock power button.

Removed and re-seated the keyboard ribbon cable.

Removed and re-seated the C-Mos backup battery.

Removed and re-seated the screen ribbon cable.

Tried F1 and F2 (apparently works on some Thinkpads).

Removed the keyboard and briefly jumped pin 19 to ground on the keyboard socket.

Ditto and briefly brushed all even nr pins on the keyboard socket to ground.

Tried battery only although known to be near dead

Even read the maintenance manual (last resort of any engineer as you will all know).

Swapped the SSD for the previously fitted HDD.

Nothing worked, not even a hint of "on". No lights, no screen, no sound, no click - nada.

What's left to try short of buying a new one?

Chris N wrote: ↑

Sat Nov 16, 2024 1:10 pm

What's left to try short of buying a new one?

Dropping it a few inches onto a hard surface? Obviously I have no idea...

"Removed and re-seated the screen ribbon cable."

Check fuse F3 (32V/3A/Fast) near the LCD-connector on the motherboard, probably blown.
Can you see anything on the LCD if you shine a torch on it?
Try an external monitor.

Have already tried an externaal monitor. No joy.

Went looking for fuses near the screen connection on the mobo but it looks like I have to pretty well do a complete strip down to get at it. Looking at an old T23 mobo and reading other infos I think replacing them, if they are soldered to the mobo, is beyond my competance level even if I can get to them and recognise them.

I'll re-assemble and see if a torch on the screen shows anything but am not hopeful. Surely the power LED would light up before the screen gets power - and it doesn't.

Thanks RealBlackStuff but I think this T400 is beyond my fixing skills.