T420S Display Switches To 50Hz On Battery Power

I just received my T420s, and I love it, except for one annoyance that I can't seem to mitigate. No matter what options I select, whenever I pull the AC adapter out, the display flickers for a second, comes back up, and sure enough it has switched to 50Hz. When I plug the power back in, it flickers again, and switches back to 60Hz.

I have tried everything I can think of. I have gone to the graphics properties, and made sure to turn off all of the power saving features when battery power is selected. I have tried setting it back to 60Hz after it has swtiched to 50Hz while on battery power. This work only until the power is connected again and then removed, at which point, it goes back to 50Hz.

This happens both with the Lenovo Display Driver, and the genereic Intel one. It happens with the preloaded image that comes with the laptop, and with a clean install. I can't figure out if it's a bug with the drivers, or with the power manager software. Is anyone else having this issue?

Thanks in advance for your help.

 

Have you checked the Power Plan under the Power Manager? Under default settings when you go to battery mode the screen will switch down to 50hz. I didn't like this so I turned the feature off. Go to Advanced Settings and under Idle Timers make sure the "Lower Display Refresh Rate" is set to "Never".

 

It may be the Intel graphics power management. The lower refresh rate saves a bit of power. Either right click on the desktop to get the Intel graphics control panel and try changing the power option or go into the advanced settings for your power plan.

John

 

The options in graphic properties are set to maximum performance for both AC and Battery. I have also made sure that lower refresh rate to 50Hz is set to never in power manager. For some reason, it still blinks and drops down to 50Hz on battery power every time without fail.

 

Does it really? I've tried switching back and forth while watching the power consumption in the Power Manager, and there's no discernible difference.

The only thing the switch to 50Hz is doing for me is producing an annoying half-second black screen when I pull the plug...

 

I didnt even know about the 50hz/60hz thing on battery mode.

It seems that my settings were at 50hz on power and battery, no wonder it doesnt look as good! I switched it to 60hz and its much better in my eyes.

 

Wait.. where is this idle timers option located again?? I cant find it.

 

It's in the "Idle Timers" section (second section) in the profile configuration page (=first page) of the power manager.

 

Its weird, mine is set to never but whenever I unplug the ac adapter it sets to 50hz.

 

So does mine. I'm assuming we're going to have to wait for an Intel driver update.

 

I had this issue for a long time as well, and honestly it stopped on it's own. I'm not sure which driver update fixed it, but I can tell you I'm using a slightly older Intel driver (8.15.10.2182) as opposed to the current lenovo driver (8.15.10.2226). There's a newer intel driver available (.2302) but I haven't tried it.

EDIT: This driver doesn't let me set it permanently, but it DOES switch properly back to 60hz when I plug in the laptop again. I can't get it to not switch down to 50hz on batt, but it's better than before when I had your issue - it would stay on 50hz after I plugged back in.

 

I have no problem when plugging in the ac adapter of it not going to 50hz. It goes back to 60hz just fine every time but the problem is that when I unplug the ac adapter it goes back down to 50hz everytime and the screen blanks out for a second.

 

Anybody ever find a solution to this? I'm having the same problem with an X220.

It always reverts to 50hz when I unplug power.

So if it's set to be 60hz when on power, the screen blanks out when I unplug/plug power.

Or I have to set it to 50hz for power too if I want to stop the screen from blanking out when I unplug/plug power.

 

I was having this problem, but fixed it for my T420s.

intel won't be releasing an update to fix this problem so instead we have to use the fix Lenovo posted on the forums. In Here

I find that these instructions are for the Optimus since I was having troubles finding the directories indicated. I went to "C:\DRIVERS\WIN\DISPLAY3\Graphics" and changed the kit33533, and followed the instructions from there. Same procedure

 

You know this to be a problem with Intel, and not Lenovo?

Just curious, why do you think Intel won't fix it? It seems a pretty odd behavior (and, imho, annoying too) that it always forces back to 50hz when switching to battery.

Also, so this affects all laptops that use the Intel chips, not just Lenovos?

 

No idea. Sorry I was merely regurgitating what was said in the Thinkpad T420s Owner's Thread. I wondered this too and decided to accept it when the problem was fixed