Ground Loop Problem

I recently bought a 22 in Acer LCD monitor but i noticed it had waves on the screen. After some research i think it is a ground loop with my laptop, every time i unplug the ac power cable from the laptop the waves go away. I have tried reading as much as i can about ground loops but i am confused and dont know how to fix the problem. I tried connecting the laptop and the monitor to the same outlet together and then separately in different outlets in my room but nothing worked. I ran an extension cord to another room and it seemed to solve the problem, so i assume it has something to do with how my room is wired? Can someone give me some suggestions on fixing this, also i heard some surge protectors can fix the problem is there any truth to that?

 

Have you tried using a power board that reduces noise interference?

 

No, where can i get one. Also i read that mabey it is the vga cable going from my laptop to the monitor. Im starting to think this may be the problem because i can plug my xbox 360 into the monitor and have my laptop plugged into the AC and i dont have any waves.

 

I had the same problem, using a different vga cable made no difference.

As flipfire mentioned a power board with a power filter in it fixed the problem
as it cleaned up the noise in the line. Most electrical retailers/stores should sell these.

Also I noticed when I used my DVI connection to the monitor instead of the vga the interference dissapeared also

 

Thanks ill look into the power board. My monitor has a dvi port but my laptop doesnt, so would it be possible to use a vga to dvi adapter?

 

Not sure, I'll grap a vga to dvi adapter from work tomorrow and try it to see if it works if you like.

I have a feeling it may not though, but will let you know

 

Hey thanks! Its Always nice to know if something will work before you spend money on it.

 

Tried the adapter and unfortunately it made no difference to the waves sorry.

So best bet as suggested is prolly the power board

 

What is your monitor grounded to? Is it attached to a coax cable? Is the notebook and monitor plugged into same outlet?

Edit: Monitor and notebook both have 3 prong plugs?

 

What you are seeing is the pictorial equivalent of the "hum loop" which used to annoy audio enthusiasts in the days of audio systems being put together from separate units. It is well described here.

As powerpack has already surmised, most likely both your monitor and the computer have grounded power connectors. The monitor cable also includes a ground connector so we then have a nice loop.

Another thing you can try is to feed the computer and the monitor from separate wall outlets. This lengthens the loop and can reduce the circulating electrons to an acceptable level. A power board with filters has already been suggested. The other fix is to cut the earth wire (usually green and yellow stripe) on one of the power leads. The easiest way to do this is to cut off the power plug and then fit a new plug with the earth not connected.

John

 

Out of my area here but could it be a phase issue? Could outlets have polarity reversed? Complete guess as the transformation to DC likely mutes that point. I suggest plugging into same outlet as is same circuit so same ground. Different circuit even if ultimately same ground could be some difference getting to it?

 

It's not normal to wire a building so that different phases are present in a room since phase-to-phase voltages are higher than phase-to-neutral.

John

 

I just bought a surge protector that has a noise filter, this is what it says on the box "Noise Filtering-EMI/RFI 150 KHz - 100 MHz up to 40 dB" i plugged both the monitor and the laptop into it and im still getting waves on the monitor. I have tried different outlets but i still get the waves. Also i ran a long extension cord to another room and the waves werent as noticeable but i could still see them. I have no idea what to do, i thought the surge protector would have fixed the problem but it didnt. Also i am using the vga cable that came with the monitor, it is fairly thin, do you think it might be the cable? Also im using Notebook Hardware Control on my laptop do you think it my be causing problems? My laptop and Monitor both have the 3 prong powercables.

 

OK so there is no coax connected to the monitor that connects to the cable company and provides a ground? Correct?

Any magnetic devices in proximity of devices or cords? Wireless devices in the home? Have you played with the refresh rate in you video cards control center? Could it be a V sync issue?

You mention cheap cable? Last resort. Wiggle the VGA cord does it have any effect on picture?

 

There is no coax cables connected to the monitor and i have not messed with the refresh rate. There are no magnetic devices near the cables and the only wireless device in my house is my house phone. Wiggling the cable didnt change anything either. It has to be a ground loop right? The only time i get waves is when i plug in the power cord to my laptop and every thing i have read suggest that this is a ground loop.

 

I agree! The fact you unplug and problem goes away shows most of my last thoughts off base.

Time to call tech support.

If I have not frustrated you too much with bad suggestions? You unplug the notebook problem gone? Unplug the battery not the power plug, what happens?

 

I unplugged the battery and left power plugged in but the problem still persist.

 

Have you got any extension lead that doesn't have a ground wire that you can use to supply the computer?

I'd been in there doing some surgery to the computer's power lead, but I've been fiddling with wires for years.

John

 

I second John - I'd try getting rid of a ground - either on the monitor or computer.

 

Im a little confused, how do i get rid of the ground ? Do you mean lifting the ground with one of those 3 prong to 2 prong adapters?

 

Yes.............

Edit: and I would start with the notebook.

 

Isnt that dangerous, and is it bad for the computer. The ground is there for a reason right?

 

No, ground isnt neccesary. Its like a safety precaution.

What gpu do you have anyway?

 

I have the NVIDIA GeForce 8600M GT in my Sager 2090. So buying a ground lift adapter and plugging it into the surge protector is ok and my laptop will still be protected?

 

Yes it will still be protected.

Have you tried tinkering with the GPU settings? It could somehow be a power management issue causing this.

 

Posting a question in Sager Forum might be useful. More likely to get the answer/solution if this is an issue. And I must say being plugged in causing it leads me to the power supply.

I wouldn't ask the question exactly the same. Just tell them what happens when plugged or unplugged. Let them decide if they think ground fault and then tell them what you did about. Fresh perspective and will know of known issues give it a shot.

I understand flips logic but don't think it is going to work in this case. flip wouldn't you also think if power mgmt features it would be more likely when unplugged?

 

I actually have this exact same problem and it's driving me nuts!

Here's why I'm confused though: If the monitor and laptop are connected to the same power bar, shouldn't their ground leads be shorted together, so therefore they should be at the same potential?? So I don't understand why this is happening

 

Yes your common sense sounds 100% correct to me. I think something in PSU or notebook is washing the power in a negative way for the situation.

At this point running ungrounded with at least one is the only option. Has it been done yet? is it working?

 

Logically, having everything grounded should stop the problem. It works fine provided there is a star configuration.

The problem we are getting here is that the monitor cable also includes a ground wire and thereby creates a loop. It's then a matter of some magnetic fields (possibly inductance where the ground ware is next to the power wires in the mains power cords) which gets a few electrons circulating around the loop. With audio equipment this comes through as a mains frequency hum. With monitors it causes some flicker.

Breaking the loop somewhere stops the problem.

It's often considered good practice to give notebooks a grounded power supply. However, I've spent a fair amount of my computing life working where my 3 pin plug is put into a 2 pin socket (via an adaptor). So far no problems. I prefer ungrounded PSUs because they have thinner and lighter power cords, but not all manufacturers share my view (see my Toshiba R500 review for an example).

John

 

John I did mention magnetic fields. I would of thought the VGA with a ground would end up using the ground of the notebook or monitor which at this point is the same.

This has to be a known issue to some? Until 3 to 2 prong no comment.

All that said John? OP said cheap VGA cord? Could that maybe help? Better shielding?

 

The problem is that the VGA cable bridges between the two bits of hardware and we can get some stray current flowing. Breaking the ground to one of the devices breaks the loop.

It shouldn't be a big challenge for monitor manufacturers to include a filter to stop this low frequency noise. Perhaps most do.

John

 

Thanks everyone for the help. I think ill get the 3 prong to 2 prong adapter for my laptop.

 

I was having the same issue sometimes with wavy lines on my external monitor. I just tried a 3 prong to 2 prong adapter and the problem seems fixed. Both the computer and monitor are plugged into the same surge protector.

Thanks guys.

 

Hi,

I have the same problem with 2 laptops:Sony Vaio and Acer Aspire.

The problem is that the Sony Vaio has only 2 prongs and the flickering is greater than with Acer which has 3 progs.

I also tried different solutions but not the 3 prong to 2 prong adapter since the Vaio has 2 and is worse.

I am gonna try the adapter on Acer but I have no other ideas for the Vaio. I've seen some VGA ground loop isolators but they aren't too cheap.

Are there any other solutions? Maybe hacking the VGA cable.

Thank you

 

I think I had soimething similar with my other screen I bought for my laptop. I used the vga-cable it came with, and the screen had ugly lines, and quality was bad. After frustrating attempts I changed vga-cables with the screen of my parents desktop, and thewonderful thing that happened was that BOTH screens worked perfectly after it!

-dunno if its important but I also have 8600GT-

sooo: have you tried other vga cables yet?

 

I really have no issues, with the North America system. It's been since the day this issue was mentioned I tried my best to understand what people are talking about... and well I can't see the problem. I have a 3 prong adapter. Maybe it has to do with how the ground is linked on the wall, and the power of the wall plug... (just a guess, of course) OR I got a manufacture error somewhere and somehow it works great.