LCD TV flickers when laptop AC power used

SlinkyMike

SlinkyMike

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Hi,

I have a headache with my LCD TV (Sony Bravia).

When using a VGA cable to connect my HP Pavilion I get a flickering screen if the laptops AC adapter is plugged in. On battery power - no flicker.

The flicker looks similar to a bad refresh rate but the only option is 60hz and it works fine when using battery power.

I have tried other LCD TVs and found the same problem.

I am hoping that there is maybe some combination of cables/adapters that might solve this as the only other thing I can think of is that it is a badly shielded power supply on the laptop board which would suck.

Has anyone else encountered this problem?

Any AV gurus got 2c to chuck in?
 
no av gurus needed

it is an earthing problem.

make sure laptop and tv are plugged into same powerstrip.

if all else fails (highly not recommended) then disconnect the earth pin from the ac/dc 3pin plug.
or just disconnect it for testing purposes, u know..
 
hmm... they aren't actually plugged into the same power strip...
Also my laptop AC has one of those circular 2 pin plugs (with the cylindrical pins and a big metal hole where the earth would be on a 3 pin) maybe that has something to do with it?

Thanks for your advice bro, cant wati to get home and hopefully have a ta-DAA! moment (as opposed to a parmp parmp parmp parrrrr sad trombone moment).
 
thing is, i'm doubting myself now that you have told me about your ac/dc

the problem happens like this. earth isnt necessarily zero volts on all devices. as you well know, voltage is potential difference.

now, you plug your laptop into the lcd screen, and what you end up doing is connecting both device's earths together, as the vga cable is earthed on both ends..this causes flicker in some cases if the two devices have different values for ground.

so the trick is to unground one of the devices.
and that is what happens when you run the laptop off battery power.

now, you say your ac/dc doesnt have an earth? that must mean it is double insulated. is there a symbol on the side of it, that looks like a square box within another larger square box?

anyway, moving on. try it on the same powerstrip, that may still help, depending on which other devices are connected to the powerstrips/plugs.

lemme know how you get on.
 
Renamed20070410 said:
so the trick is to unground one of the devices.
and that is what happens when you run the laptop off battery power.

now, you say your ac/dc doesnt have an earth? that must mean it is double insulated. is there a symbol on the side of it, that looks like a square box within another larger square box?
Click to expand...

Thats what I was thinking but the wrong way round - on battery power its not earthed so that would disprove the earthing theory but you make a lot of sense when you mention ungrounding one device.

I don't see anything similar to that symbol you describe but the round 2 pin plug has a metal sheath like thing where the earth should be, maybe this can be inserted optionally?

Gotta check that out but 1st port of call is the single power strip scenario.

I'll update this thread cos I have seen numerous similar queries whilst googling but not one solution.

Thanks again dude.
 
The round 2 pin plug you speak about, sounds like the German standard. They have ground on the sides of the plug (see link).

If this is the case, you could by a multi-plug in most shops with support for it.
 
Nod said:
The round 2 pin plug you speak about, sounds like the German standard. They have ground on the sides of the plug (see link).

If this is the case, you could by a multi-plug in most shops with support for it.
Click to expand...
Or chop off that plug and substitute an earthed three prong SA one?
 
bwana said:
Or chop off that plug and substitute an earthed three prong SA one?
Click to expand...

That will work too. I do know that some vendors void your warrentee if you remove their plugs. So check the manual before snipping anything off.
 
Nod said:
That will work too. I do know that some vendors void your warrentee if you remove their plugs. So check the manual before snipping anything off.
Click to expand...
I didn't know vendors were even allowed to do that. Even so you can always buy a new cord for the laptop right?
 
bwana said:
I didn't know vendors were even allowed to do that. Even so you can always buy a new cord for the laptop right?
Click to expand...

Should be possible yes. It will just save some time/money if you make sure about their warrentee conditions before snipping the plug off.

Even better, send their technical support a email, and get it in writing that you can actually do it. Won't take much time, and will protect you in the event of malfunction.
 
Nod said:
The round 2 pin plug you speak about, sounds like the German standard. They have ground on the sides of the plug (see link).

If this is the case, you could by a multi-plug in most shops with support for it.
Click to expand...

Thassa one!

Best I get an adapter to suit cos basically that means i'm currently (pun?) running my laptop unearthed at the mo.

Also: I'd not be surprised at all to find that ridding myself of that plug would void warranty. Not sure if its common but even using RAM thats not got the 'HP part' sticker on it will void warranty.

Got lots to tryout this evening... I'll report back 2mo, cheers dudes:)
 
Last edited:
The power supply has two parts, the "kettle cord" which plugs into the mains, and the transformer part that plugs into the Laptop. Just get another power cord.
 
Ok, update as promised: problem solved!

Basically I pillaged and old Compaq for the power cable part (long since snipped and 3 pronged) which solved the problem without exception in any way.

Thanks for all your help and suggestions etc. ...wrong power cable supplied by a local supplier - who'd-a-thunk-it?
 
Yea, I must admit: if you haven't had this problem before and simply had one of those 'Grissom moments' where the problem solves itself in your head then you're a right little five speed gearbox! :)
I'll go even further and say that if you aren't working in AV somehow or some related filed you may have missed your calling.
Either way - thanks for you help and shot to everyone who tossed in some advice - my media centre is super warm n fuzzy at the mo ...just need to get my hands on the DiNovo keyboard and I'll be in mediavana;)
 
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