T41 Thinkpad - screen goes black after successful boot up

[g_lovett2000]

I recently bought a used T41 Thinkpad as a laptop for my son. The machine is several years old and I payed $40.00. It is a great little machine with wireless connectivity for browsing, basic MS office use, and older gaming applications.

My son reported that he was having problems with the machine after having used it extensively for about 4 weeks.

Symptoms: Press power on, Fan Starts, Computer boots successfully into Windows, Screen goes black, cannot see what is happening on machine, have to press and hold power down to turn off machine. If I try to immediately restart it, it may start but will fail faster each time. Eventually will not start at all. If I wait a while, it will start again and repeat the pattern.

I do not believe the CPU is actually shutting down because even after the screen goes black I can open the DVD drive, put a disk in and it will spin up. I can't see the screen, but I can see the disk being detected and spinning up. The CPU cooling fan is also starting back up and running as well. I'm assuming this means the CPU is still running.

I believed initially that it was a screen/monitor issue. I connected it to an external monitor to see if it prevented the screen blackout, but it reacted the same way. Therefore I believe I have eliminated the monitor as the issue.

I tried this with the battery connected with and without external power cable attached. I also tried with battery removed and power cable attached. The same symptoms occurred in all cases. I do not think the issue is power supply related.

I then wondered if the thermal compound between the fan and CPU might have aged and broken down. I removed the fan, cleaned off the old compound, applied new compound and reassembled the machine. It started up and exhibited the same symptoms. I also noted when doing this, that the fan assembly does NOT cover the GPU as it does in some photo's I've seen of other machines.

I considered and researched the possibility that the CMOS battery is beginning to fail but the symptoms don’t seem match that problem at all.
I've wondered whether the fan itself may be failing in some way even though it runs as the computer is booting and gives no fan error messages. Since the CPU seems not to be shutting down and the fan continues to run after the screen goes black I don't think the fan is bad.

Based on all the above I would guess that the GPU may be shutting down based on heat. However, I'm not sure why it would begin doing that all of a sudden. But it would explain why the screen blackout occurs on both the internal and external monitor, as well as why the screen goes blank while the CPU is still running.

I'm about out of diagnostic ideas to pursue. I’m not sure what else might be causing the symptoms but would appreciate any thoughts or advice from those with more experience in these laptops.

[RealBlackStuff]

Welcome to the forum.
Yours is a rather common problem of the GPU becoming unstuck.
See this thread (and a few other 'Stickies' in the T4x forum): http://forum.thinkpads.com/viewtopic.php?f=2&t=65505
It needs reballing of the GPU and maby also of the Southbridge.
Alternatively, get another motherboard.