LCD displays flickering using VGA but HDMI not flickering

• Nov 27, 2019

• #1

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i200yrs

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Hello again...we have about +1000 of lcd displays in the fab, around 40% of it are flickering (but text still readable). Our facility staffs check all groundings from those flickering but all were fine. During investigation, the flickering goes out when using HDMI instead of VGA. But it is not cost effective to replace all with HDMI...Thus, we need some inputs from you experts on how this flickering happens when using VGA but other display ok with VGA. Need suggestion on how to resolve it in minimal cost. Thanks in advance.

 

• Nov 27, 2019

• #2

KlausST

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Hi,

What technical informations did you give that we can use to find a solution?

When a monitor flickers, then usually it's because
* monitor type: input signal range
* graphics card output signal: resolution, frame rate,
(Maybe even a mature "interlaced" signal is output by the graphics card)
* noise introduced into the monitor cable (signals): cable type, shielding type, cable length

Klaus

 

• Nov 27, 2019

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is the 'flickering' exist on the monitors from the beginning(when monitor is new ) or is it a new problem surfaced slowly with time?

 

• Nov 28, 2019

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srizbf said:

is the 'flickering' exist on the monitors from the beginning(when monitor is new ) or is it a new problem surfaced slowly with time?

Click to expand...

Yes..since the start about 10yrs ago...only this moment people decide to take action "(.

 

• Nov 28, 2019

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OK today we found something new today....when we dont connect the ground to the cpu and monitor supply the flicker goes out. I mean from the ac power plug going to the pc/monitor only live and neutral connected (no earth ground), it works...So weird and not safe...any idea guys? Is there something need to do to the video card groundings or monitor groundings?

I found this from google --> https://mrgnome.wordpress.com/2009/06/12/external-monitor-flicker-laptop-ground-loop-problem-solved/
It should be safe, but really appreciate if someone can help me understand this...thanks

 

Last edited: Nov 28, 2019

• Nov 28, 2019

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what is the voltage between ground and neutral?

 

• Nov 28, 2019

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KlausST

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Hi,

What do you expexct?
We don't know about the cable, the wiring....you just give vague and incomplete informations.
And it seems you don't read our posts....

Klaus

 

• Nov 29, 2019

• #8

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KlausST said:

Hi,

What do you expexct?
We don't know about the cable, the wiring....you just give vague and incomplete informations.
And it seems you don't read our posts....

Klaus

Click to expand...

My apology mr Klaus...i read your posts am done checking your advice in post#2....but all ok when we compared with non-flicking units.

- - - Updated - - -

srizbf said:

what is the voltage between ground and neutral?

Click to expand...

OK let me check this out...we missed to measure this, good tips....thanks

 

• Nov 29, 2019

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From one of the flickering unit ground & neutral is 1.36Vac....but from good unit is 0.7Vac....is it safe to add jumper to short ground and neutral from flickering unit? thanks

 

• Nov 29, 2019

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ZASto

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NEVER short Ground and Neutral.

 

• Nov 29, 2019

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the flickering unit ground wiring has problem . Trace the ground wire and follow it to the point where it is actually grounded. There may be corrosion or even loose connections in the path.

shorting is not advised.

 

• Nov 30, 2019

• #12

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srizbf said:

the flickering unit ground wiring has problem . Trace the ground wire and follow it to the point where it is actually grounded. There may be corrosion or even loose connections in the path.

shorting is not advised.

Click to expand...

We have tried to connect the flickering unit ground and non-flickering unit ground using jumper wire but not helping....if the ground have problem, why using hdmi doesn't flicker...It flickers only when using vga...any idea guys? thanks

 

• Nov 30, 2019

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KlausST

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Hi,

any idea guys?

Click to expand...

VGA = analog. Any influence in analog signals will be shown on the screen
HDMI = digital. More tolerant against noise, until the noise is big enough to make HIGH --> LOW ore vice versa.

Klaus