SL400 external VGA monitor random switching

[400owner]

Hi,

I have a SL400 with the nVida 9300GS graphics card.  Since day 1 I've had a problem using an external monitor (ViewSonic NX1932w) on the VGA connection.  When I switch to the external monitor using either the Lenovo Presentation Manager or the nVida control panel, it will randomly and inconsistently switch back to the laptop display only and then back to the external monitor.  This is true if I use the external monitor alone, or in dual view.  Sometimes it will happen once every few minutes, sometimes not at all, and sometimes continuously back and forth until I manually switch back to the laptop only.  Rebooting may or may not help.

I've reinstalled the updated nVidia display drivers and the Presentation Manager app from the Lenovo website numerous times.  I've updated the BIOS.  I ran the PC Doctor hardware test on the video system and it passed.  I sent the unit in for warranty service, and it came back with an updated BIOS and a factory reinstall of the hard drive, which did not fix the problem.  I called Lenovo support again and was told to reset the power manager settings, which I've adjusted every which way and did not fix the problem.  I disabled the Presentation Manger entirely using only the nVIda control panel and that did not fix the problem.  I disabled the nVidia control panel using only the Presentation Manager, and that did not fix the problem.  I have not yet tried connecting through the HDMI port, though I have ordered a cable to do so.  It does seem to act worse when I first boot it up and try to switch.

Any suggestions on how to fix this would be appreciated.  Thanks!

[Xeogin · Accepted solution]

I'm not sure, but this might work:

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 Quoted from http://forum.notebookreview.com/showthread.php?t=166532

1. Disable TMM

This tweak is responsible cutting system start time 3-5 seconds and
eliminating that blank screen flash when you start Vista. This normally
occurs when Vista searches for external monitors on start up of Vista.
If you are not using an external monitor, or don't switch back and forth
always...turn TMM off.

Here's how to fix that annoying black flicker on boot:

1. Go start/control panel/administrative options/task scheduler.

2. On the left-hand side, click "Task Scheduler Local" (you should already be there, but just in case).

Expand "Task Scheduler Library," then "Microsoft," then "Windows," then click "MobilePC."

Up top, you'll see a task called "TMM." Click it, and on the right-hand side, click "Disable."

If you use an external monitor occasionally as I do, just press and hold FN and press F8 twice to switch monitors.

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I'm aware this is suppose to be a boot time tweak, but if this task were running during normal operation, it would have the same or similar effects as your problem, so I'm just proposing you try this, and even if it doesn't work, you would still help with your boot time. ^^;

[400owner]

This worked, thanks!  It's been stable for days now.  It randomly decides which screen (or both) to boot to now, but the really annoying blinking back and forth is gone and I can use Fn+F7 to switch back and forth.  Greatly appreciate the help!!

[bdgrubbs]

Hello,

I have the same problem with my T520.  It occurs with two different monitors and two different VGA cables at my home and office.  I have Windows 7 and followed the guidance above, but my "DisplayLink TMM Control" is already disabled.  On that same screen, I have a "HotStart" that is still enabled.

Any thoughts (I realized I should start a new post but I couldn't find the link to do that.  Probably right in front of me somewhwere).  Fixing this would be a huge help as it's very, very annoying.