Thinkpads Forum

Hi - T400s treats me generally well except for this small issue. It goes to black and then back (total about one second) when I switch power source from AC to battery (dim - beep - black - back to dim), or the other way around. Quick google did not give me any solutions. I wonder if it is just me or someone else may have the same problem, since I did a few tweaks of the system afterwards and this does not look like a hardware issue.

Much appreciated - thanks!

Mine does this when the screen blanks while on battery; there is a brief flash, then black.

Mike

The same thing happens on my T400, although I suspected it was the Power Manager trying to switch to integrated graphics (even when it was already on integrated).

Weird.

Check your power management settings in your video card or the power manager itself - you may be seeing the video card switching to a lower refresh rate (from 60 to 50Hz).

It won't switch from discrete to onboard automatically - it has to be done manually. And the switch is more than just a flicker... it's two blanks, with a total desktop redraw. I suspect the quick flicker is a refresh change and can be disabled if it's troublesome. I'm not sure exactly how much power you're actually savings by dropping 10 refreshes per second. Although while checking my settings I switched to the on board graphics card and upped the power savings settings in the Intel GMA control panel to maximum and gained 49 minutes in my power meter.

For what its worth!

jasonth wrote:Check your power management settings in your video card or the power manager itself - you may be seeing the video card switching to a lower refresh rate (from 60 to 50Hz).

It won't switch from discrete to onboard automatically - it has to be done manually. And the switch is more than just a flicker... it's two blanks, with a total desktop redraw. I suspect the quick flicker is a refresh change and can be disabled if it's troublesome. I'm not sure exactly how much power you're actually savings by dropping 10 refreshes per second. Although while checking my settings I switched to the on board graphics card and upped the power savings settings in the Intel GMA control panel to maximum and gained 49 minutes in my power meter.

For what its worth!

Thanks jasonth - this solved the problem. Right click on desktop -> Graphics Properties -> Display settings -> Power Settings -> Custom/Modify -> Uncheck Intel Display Refresh Rate Switching Technology

Awesome! This has been bugging me for the last 6 months and I couldn't find an answer anywhere. Finally!!!

Even I get lucky with a diagnostic once in a while! Very glad I could help.