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Laptop to lcd connection via vga - static sound and flickering problem

Last response: in Other Consumer Electronics
February 13, 2011 7:11:33 AM


I have a toshiba l635 laptop ang lg lcd 32 inch, which has 2 hdmi, vga, component connection and RGB audio in. unfortunately my laptop has no hdmi but vga. Now I have connected my ps3 via hdmi to lcd and laptop via vga cable ( oridinary cable, not branded one) I get the video and for audio simple head phone jack on both sides which I connected to RGB audio in on lcd. I get video and audio good, but the problem is I get a static buzzing sound and page on lcd flickers when surfing the internet.

I have noticed that in ur blog, there was a discussion regarding this static sound, which was ? due to three pin plug, but I have a flat 2 pin plug connected via a extension cable from main source, which also connects all the plugs from lcd, ps3 and my tv satellite reciever.

Can you please guide me what to do to get rid of this noice and flickering. is it due to cheap cable or power supply? will the good quality cable like monster solve my problem?

Your expert advice will be appreciated.


February 13, 2011 11:38:16 AM

when you unplug the laptop from the television.. does the static sound go away?
how about unplugging the ps3 from the television.. does the static go away?

is there static with nothing plugged into the television?

its probably a problem with a lack of isolation between one or all of the circuits.
what happens is.. the power from the wall gets 'isolated' from the rest of the circuit because of the transformer.
that means you have all these 'floating' circuits and none of them are grounded properly.
because what happens is, one of the circuits has excess voltage and that voltage will bleed into another circuit if given the chance.
the other circuit is isolated and therefore the extra voltage doesnt have any place to go and it will affect something.

perhaps the television does have a proper ground.. but that doesnt mean the ground can make its way from the audio input all the way to the power transformer and into the outlet on the wall.

anyways.. that excess voltage can be positive or negative.
if positive, the voltage is pushing onto other components that are already receiving proper voltage.
if negative, the voltage is sucking on other components and that throws off the design of the circuit.
its like having a traffic light with both directions of traffic on a yellow light rather than one red and one green.
the noise you are hearing is the confusion of the drivers because they cant cross the street safely.

a whole lot of circuits nowadays pulse to a rhythm of a PLL chip or crystal.
and the entire circuit handles electricity to the heartbeat until everything is fully charged.
if you are using the circuit.. obviously the circuit cant remain fully charged and steady.
instead it loses energy as fast as it recharges.
if you make the circuit slur.. the recharging voltage will be excessive because the pieces that are supposed to be recharging arent listening with full attention.
that extra electricity can simply bleed into the circuit and create noise (when in analog form)
if it was digital form.. it would be seen as jitter at the least.
at worst, it would start to change 1's and 0's .. which is corrupted audio.
usually the convertor chip will have jitter tolerances.. but something might burn up and fail from torture before it changes any 1's and 0's
i'd guess that the ground loop would only cause latencies of the arrival of said 1's and 0's
latency as small as nanoseconds.. which means the convertor chip wont care.
it might run hotter because if taking on extra voltage.. but it will function as long as the temperature is within limits.
again, i would guess that the extra voltage is simply lingering on the circuit traces and being picked up by all things meant to 'read' from those traces.

say the extra voltage comes in through the audio jack and passes right through the digital to analog convertor and goes into the amplifier section.
it wouldnt be so loud if it wasnt for the amplifier thinking the extra voltage is audio that is meant to be amplified.

because the power supply uses a transformer to step-down the voltage from the wall outlet.. all connections to another piece of hardware should have an isolator.
but that adds cost to the project and since sometimes it isnt needed.. they dont bother to install one on the circuit board.

the flickering can be from the same excessive voltage.
it would be a little bit weird to hear that a graphics card isnt properly filtering its power.
but when you have excess voltage on the run like a rabbit.. theres a chance that it is coming from the audio input and into the video filter circuit.
or maybe its something simple like a refresh rate mix-match and what you are seeing is 'tearing' of the screen because of the mix-match.
maybe your television has a very weak circuit (which amounts to sensitive).

maybe the ps3 is also adding extra voltage to the circuit.. and together with the laptop, it creates more than the television circuits can filter.
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