Solution: Secondary LCD monitor flickers when laptop connected to AC power
A secondary monitor is a very useful thing when you do anything that requires multitasking. In my case, as a web developer, it’s pretty much essential, at the very least being a huge productivity booster. I had this strange issue with my laptop, though, wherein my secondary LCD monitor would flicker if my laptop was plugged in (connected to AC power). Strangely and baffling to me, though, if my laptop was running from its battery, there was no problem at all. Naturally, this led me to suspect my power supply, my laptop’s AC adaptor, the laptop battery, the power bar, the LCD itself, and even my display drivers. Nothing helped.
Solution: THE VGA CABLE. Now, conventional wisdom would probably lead one to assume that the VGA cables that come in the box with your new LCD monitor would be of at least relatively decent quality. If you’re having the same issue that I had, this is incorrect. Apparently most LCD manufacturers are too cheap to include higher quality dual shielded VGA cables with their monitors. The VGA cable that came with my monitor (BenQ T2200HD) only had a shield (the round thing an inch or so from the plug(s)) for one plug. Replacing the cable with a double shielded cable immediately resolved my problem, to my great relief.
I Googled for untold hours trying to fix this issue, and found some similar posts, but none with a solution. I posted on a tech support forum and none of the techies seemed to know. I am telling the world: GET A DUAL SHIELDED VGA CABLE! Shame on manufacturers that include substandard accessories with their products!
I sincerely hope this post reaches those who need it. If the post happens to help you, leave a comment with your story if you don’t mind =)
May 16th, 2009 at 2:29 am
I observed the same problem and your solution was right on. A cheap VGA cable was the culprit. I swapped out the cheap cable which came with the NEW monitor for the dual shielded cable and it worked. The damn flikering was giving me a head ache. I got a great deal on the monitor and now I know why. Thanks a lot for your post.
May 16th, 2009 at 5:42 am
No problem Michael – glad I could help!
June 9th, 2009 at 2:50 pm
Awesome tip, I just noticed this myself when plugging in my AC Adapter to my laptop, the screen started to flicker, especially when using the mouse in either monitor. I am thinking about running hdmi to dvid instead of VGA, hopefully this will also remedy the issue.
By the way, this is the second BenQ T2200HD I have owned, I returned the first to the manufacturer under the 14 day zero defective pixel warranty it came with – it had 2 bright stuck pixels, which could only be seen against a dark background; my new monitor also has a stuck green pixel near the bottom, which is very annoying. I just got this monitor back, and am not sure if I should return it again, given the wait and effort involved returning. I might try and fix with JScreenFix. Have you experienced any issues with your monitor regarding stuck/dead pixels?
Thanks for the tip!
June 9th, 2009 at 11:55 pm
Luckily my monitor seems to be pretty good that way. If you keep having trouble with flickering, at least you’ll know it’s the cable and not the monitor =)
Anyhow – glad that my blog post is helping people out! Good luck Mike!
PS: Just curious – how much did you pay for your monitor? I got mine for about USD 165 or so.
August 8th, 2009 at 2:18 am
Thanks for saving me time trying to find solution. This seems to be a problem for laptops with VGA output very close to battery input. (Mine is a Gateway.) For now I have twisted VGA cable as far away from the power cable and the flickering is greatly diminished. Am heading out to get a new cable.
August 23rd, 2009 at 6:42 pm
The real problem is dirty AC power.
August 27th, 2009 at 3:33 am
Hmm, that’s interesting. What’s the solution to dirty AC power?
October 12th, 2009 at 5:55 am
Thank you! I have been having the same problem with a 19 in Dell monitor and a e6400 latitude laptop. The AC input to the laptop is right next to the VGA cable – I swapped the cables and viola! No more (or a lot less) flickering.
October 18th, 2009 at 10:27 pm
Was the extra monitor plugged into its own power source? Or just running off the laptop?
I just bought a monitor to supplement my tiny laptop screen and can’t get it to work!!
October 21st, 2009 at 6:11 pm
Its own power source. I actually haven’t ever heard of a monitor running off a laptop’s power source before, so I assume you need to plug it in almost regardless of model (there might be something super fancy I’ve never seen before, but I kinda doubt it at least for now).
October 23rd, 2009 at 3:11 am
This totally fixed my problem as well. Now to uninstall all the junk HP packaged with my monitor that didn’t help at all! Cheers!
November 21st, 2009 at 12:35 am
Thanks, I’m having the same problem with a new laptop and computer and will try your fix. It’s a relief that I’m having the same problem as other people because it’s driving me crazy and the IT support has not been helpful.
November 21st, 2009 at 2:14 am
Glad to hear this post helped you, Nicky. Make sure you buy a high quality dual shielded cable, and all should be good
There are also some low quality (cheap) cables that pop up from time to time, that also may cause issues.
December 18th, 2009 at 2:09 pm
Another fix for the static flicker problem is to get one of those adapters that turns your AC adapters 3 prong plug into a 2 prong plug. The adapters removes the ground of your power supply. For some reason this completely solves the flicker static problem in using an external monitor. I believe the static comes from interference in the ground. Just be aware that you won’t have a ground anymore so use a good power surge strip.
My Levono laptop interestingly does not have a ground on it’s power supply and I don’t have this flicker problem at all when using it. My Gateway laptop on the other hand does have a third ground prong and exhibits the flicker issue. The problem was solved with the adapter.
Give it a shot, the adapter is $ .75 cents at home depot.
December 18th, 2009 at 5:26 pm
That’s interesting that it worked for you, Jimmy. I am actually not all that sure that will work in all cases, though, because for a random reason (I broke off the third prong because I had to charge the laptop in a place with only two prong outlets), the laptop that had that issue only had two prongs and not three. The dual shielded VGA cables are not that expensive either, as far as I know. Recently I had another interesting experience though with “cheap” dual shielded VGA cables (in China), so be aware that not all cables are created equally.