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bmihai
SCSI Port
Posts: 34
Registered: ‎06-24-2012
Location: Romania
Views: 4,186
Message 1 of 8

VGA output noise

When I use the VGA port and plug in the power cable into my T430 I notice faint horizontal lines flickering on the external monitor, in areas of certain shades of gray. It is faint, but visible. I have auto-adjusted the external monitor.

 

The flickering is visible even when the laptop is not plugged into a power outlet, but not as visibly.

 

This is quite disappointing, after having come from an HP *netbook*, which displayed none of these problems. Is this normal?

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T430: i7-3520M, NVS5400, 1600x900, SSD+HDD. Debian + Windows7.
Remeniz
Token Ring
Posts: 79
Registered: ‎06-12-2012
Location: Peterborough - England
Views: 4,177
Message 2 of 8

Re: VGA output noise

I had the exact same problem with my T61. Turns out to be noise coming from an earth loop. So, I isolsated the earth pin on the power supplly and the problem dissapeared.

 

Disconnect the PSU and see if you still have problems.

 

If the problem dissapears when running from battery then consider removing the noisy earth loop.

 

EDIT: Just realised that your getting the same problem running on battery.

 

 

_____________________________________________________________________________________________________
T410(2537) -- i7 620M - Intel HD GPU (1440 x 900) - 8GB RAM - 128GB Crucial M4 SSD - 250GB Hitachi HDD - Windows 7 & 8 Pro
bmihai
SCSI Port
Posts: 34
Registered: ‎06-24-2012
Location: Romania
Views: 4,171
Message 3 of 8

Re: VGA output noise

Thanks Remeniz,

 

There is actually no grounding connection on the power plug, so I don't think that's what's causing it.

 

Also, on second look I think the much weaker flickering I see in some shades of gray when not plugged in may be just be the 6-bit monitor dithering doing its thing. I admit I never looked that closely for flickering before seeing the stronger one from the PSU.

 

It's not a dealbreaker, but it's a little disappointing this is happening, in the exact same setup that it wasn't happening with a different, much cheaper, machine.

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T430: i7-3520M, NVS5400, 1600x900, SSD+HDD. Debian + Windows7.
Remeniz
Token Ring
Posts: 79
Registered: ‎06-12-2012
Location: Peterborough - England
Views: 4,160
Message 4 of 8

Re: VGA output noise

Yea, I think the noise enters the machine via the Signal (Center pin) on the PSU connector.

 

It didn't matter if I isolated the earth pin, at the mains, on the external monitor or the T61  PSU, just breaking the earth loop completely cured the problem.

_____________________________________________________________________________________________________
T410(2537) -- i7 620M - Intel HD GPU (1440 x 900) - 8GB RAM - 128GB Crucial M4 SSD - 250GB Hitachi HDD - Windows 7 & 8 Pro
DigBlueprint
What's DOS?
Posts: 1
Registered: ‎07-25-2012
Location: United States
Views: 4,118
Message 5 of 8

Re: VGA output noise

Unfortunately, I noticed the same issue on my brand new T430 as well as that of a friend (identical configuration).  The problem *almost* completely resolves when the PSU is disconnected, although some faint horizontal banding/waves are noticeable. 

 

How might you suggest I disconnect the ground loop on my PSU connector?  Might there be another way around.

 

I know that using a mini displayport to DVI (or HDMI) adapter would solve this problem, but it's still disappointing nonetheless.  This is the first laptop I've owned with this particular issue.  One would think that as builders of business-class laptops, Lenovo would ensure that its products could be used to display presentations flawlessly...

kbirger
Paper Tape
Posts: 5
Registered: ‎04-15-2013
Location: Boston
Views: 3,600
Message 6 of 8

Re: VGA output noise

I'm currently experiencing the exact same thing with both a 90W and 65W lenovo power adapter, both ungrounded. Problem is reduced when laptop is not plugged in, but is still present.

 

Starting to think that it's a defect in the laptop and that it will need to go in for repairs (it's brand new).

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buddha1987
Punch Card
Posts: 39
Registered: ‎08-30-2013
Location: Canada
Views: 2,140
Message 7 of 8

Re: VGA output noise

Hello guys,

I have the exact problem in my T430. I found if I disconnected the power cable, then the noise disappear. But the laptop needs the power supply. So how do you fix this problem?

Thanks.
buddha1987
Punch Card
Posts: 39
Registered: ‎08-30-2013
Location: Canada
Views: 2,140
Message 8 of 8

Re: VGA output noise

Hello Remeniz,

how to breake the earth loop in PSU?

Thanks.

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