Problems connecting a laptop through the SVideo port to a Display VGA input

[jeproca]

Hi Everyone!

I guess I am making a really basic mistake but I can't fix it.

I have an HP laptop connected to a LG display screen via a vga cable. A couple of weeks ago we noticed that the signal was not stable. I revised the connection, checked the cable,etc etc and it seems that the VGA output is having some kind of trouble. My idea was to send the laptop signal from its SVideo output to the display screen. The dis`play screen has only a VGA input therefore I ended up buying a cable which has 3 terminals (VGA to SVideo and RCA video I believe). I got the cable today, pop it up and nothing. With the Fn+F4 combination I see that the display is getting some input but then I have a message on the screen saying something about a different range 15.6KHz and 24 Hz.

Am I trying anything impossible or there's a basic thing I am missing to make it work.

Any help appreciated. Thanks everyone. Cheers. Josep

[jeproca]

Anyone out there who can give this castaway a hand?

[Bjs]

Take the cable and give it away ... svideo to vga out is not impossible but those cheaper cable types fail ... there only meant for vga to svideo ... not reversed.

The problem is lack of pin inputs to outputs ... vga has and requires more than svideo delivers.

This device is more like whats needed as the conversion unit needs it's own processor.

[surfmonkee]

my first tip would be to try a different screen resolution on the laptop.

you might have to go down to 800x600

[jagabo]

Take the cable and give it away ... svideo to vga out is not impossible but those cheaper cable types fail ... there only meant for vga to svideo ... not reversed.

And even then they only work with VGA ports that already have s-video on otherwise unused pins. They don't convert the VGA signal to an s-video signal, they just connect pins on the VGA port to the s-video connector.

My idea was to send the laptop signal from its SVideo output to the display screen.

Even if your monitor has an s-video input (or you use a TV) the quality will be very low. A fuzzy 640x480 like in this sample image:
https://forum.videohelp.com/threads/283861-VGA-to-S-video?p=1756748&viewfull=1#post1756748

[Nelson37]

The VGA input will give your best quality.

Please supply more information regarding "not stable" and "having some sort of trouble". Also what changes were made to the PC "a couple of weeks ago".

Most likely the resolution or refresh rate was changed to one the monitor does not fully support.

[jeproca]

Tksto everyone for the assistance. Let me explain a little bit better what happened. Allow me to say that no changes were made to the laptop or anything. One day the image on the display started looking like ... sort of blurred and also sometimes the background lightness had been reduced looking like dimer, we could also define it as having a strange snowfall effect (whether I may call it like this) on the screen ...

I checked the vga cable, I checked the display and nothing wrong. Then my asumption was that the vga output from the laptop was suffering from some inestability. Right now I am typing this watching at the display and it looks great but who knows when the bloody thing will start again.

My idea was buying on the net a cable (costed me 4 eur including transport so no big deal) which has on svideo end (female) and a vga male end. Attached to this I am using a svideo cable(male-male). The laptop does send the signal to the display cause the display gets from standby mode to on mode but there is a message on the display screen stating "out of range 15.6KHz and 24 Hz".

My next option (not to disassemble the laptop cause that's too much for me) would be buying a refurbished docking station ( HP Quickdock) which has a single cable to be connected to what HP calls the Expansion Port 3. My big question is whether the vga signal coming out from that Expansion port would be the same one coming out from the damaged vga outport (therefore unstable) or not. In case anyone can bring some light on this issue that would also be great. Thanks everyone! Cheers
Jep Roca (Girona / CATALONIA)

[jagabo]

My idea was buying on the net a cable (costed me 4 eur including transport so no big deal) which has on svideo end (female) and a vga male end. Attached to this I am using a svideo cable(male-male). The laptop does send the signal to the display cause the display gets from standby mode to on mode but there is a message on the display screen stating "out of range 15.6KHz and 24 Hz".

It's seeing a voltage on whatever pin it uses to sense the presence of a computer (probably the green input), but that doesn't mean it will have any idea what to do with it. VGA and s-video are very different signals. You cannot convert one to the other with a cable.

My next option (not to disassemble the laptop cause that's too much for me) would be buying a refurbished docking station ( HP Quickdock) which has a single cable to be connected to what HP calls the Expansion Port 3. My big question is whether the vga signal coming out from that Expansion port would be the same one coming out from the damaged vga outport (therefore unstable) or not.

The VGA port on the docking station is probably the same source signal as the VGA port on the laptop. Unless the problem is with the connector the docking station probably won't help. It sounds like you have a heat related problem (the aging or defective video DAC is screwing up when it gets hot). An external laptop cooler might help.

[edDV]

How long is the VGA cable? Anything over 15 feet needs double shielding. Longer needs a premium cable or repeater. VGA gets more unstable as the cable goes longer.

Try a different computer to see if it is a computer problem.

[jeproca]

Cable is 1.5m long (make it 5 feet). In case it was a heating problem I guess it would appear after some time using the computer but it does happen straight from the begining. This is a joke, when I wrote the last post it was workign perfectly and now it has started again doing the same thing. I was wondering... Can an interference make it behaving like this? Thanks for the explanation about the Quickdoc, that means it's not the way to go. Damn, all ideas seem to fade away now. I guess I will end up opening the bloody laptop and taking a look, the problem is that in case I need to change the vga card the HP Service fellas will keep it for 3 months....Scary!

[edDV]

Cable is 1.5m long (make it 5 feet). In case it was a heating problem I guess it would appear after some time using the computer but it does happen straight from the begining. This is a joke, when I wrote the last post it was workign perfectly and now it has started again doing the same thing. I was wondering... Can an interference make it behaving like this? Thanks for the explanation about the Quickdoc, that means it's not the way to go. Damn, all ideas seem to fade away now. I guess I will end up opening the bloody laptop and taking a look, the problem is that in case I need to change the vga card the HP Service fellas will keep it for 3 months....Scary!

In most laptops it isn't a separate card. The video chip is part of the motherboard.

Some more ideas.

- Use a laptop cooler
- Try a USB2 to VGA display device. These are intended for Powerpoint type presentations not gaming. For example

http://www.google.com/products/catalog?hl=en&expIds=17259,18167,26637,27060,27164,2717...ed=0CEUQ8wIwAg#

[edDV]

That particular model is limited to 1280x1024 resolution. Others may go higher.

[jeproca]

Wow, didn't know you could transfor a usb port into a vga output. Mindblowing! I can't understand how the usb port can channel (source) the image data! Just one quick question, where is this image data coming from? In case it does come from the video card on the motherboard I would end up getting the same effect I guess or does it source that particular signal from a different end?

Thanks for help! Cheers

[jagabo]

It's basically a graphics card that plugs into a USB port instead of a PCIe slot. They're fine for office type apps but not good for HD video, gaming, etc.

[Nelson37]

First, are you absolutely certain the cable is not coming loose? Do you have a cat? When the display goes "bad", does it become "good" with no action from you at all, or only if you reboot or check the cable or something else?

Is the laptop display active at the same time, and if so does it show problems at the same time? If not, what if you disconnect or disable the VGA?

If the laptop's built-in display does not show the problem while the VGA output does, that would tend to indicate that the problem is isolated to the port itself, meaning that the docking station might provide a solution.

However, any problem that is on the mainboard is a BIG problem, especially on a laptop, and if you can get this fixed under warranty or apply the money you would spend on a docking station to do so, that would be the better way to go, unless the dock is pretty cheap.

[jeproca]

[QUOTE=Nelson37;2028997]First, are you absolutely certain the cable is not coming loose? 100% SURE Do you have a cat? NO CATS-NO DOGS-NO ONE MESSING AROUND THE LAPTOP BUT ME When the display goes "bad", does it become "good" with no action from you at all, or only if you reboot or check the cable or something else?NO NEED TO REBOOT.ALL OF A SUDDEN GOES WRONG AND THEN SIMPLY GOES BACK TO NORMAL OPERATION.RIGHT NOW THE SCREEN IS BAD AND I CAN SEE THIS SNOWFALL EFFECT AND SOMETIMES ALL OF A SUDDEN THE IMAGE GETS BRIGHTER AND THEN BACK TO THIS SNOWFALL EFFECT AGAIN

Is the laptop display active at the same time, and if so does it show problems at the same time? If not, what if you disconnect or disable the VGA? LAPTOP SCREEN WORKS FINE. SAME SH... HAPPENS REGARDLESS OF WHETHER BOTH MONITORS ARE ON OR JUST THE DISPLAY ONE.

If the laptop's built-in display does not show the problem while the VGA output does, that would tend to indicate that the problem is isolated to the port itself, meaning that the docking station might provide a solution.MAKES SENSE TO ME BUT I HAVE NO IDEA HOW THIS PORT IS CONNECTED TO THE VIDEO BOARD AND WETHER THE BUILT IN DISPLAY GETS THE SIGNAL FROM THE SAME SOURCE AS THE VGA PORT OR NOT. THIS HP EXPANSION PORT 3 SOUNDS LIKE A PANDORA BOX TO ME, HOW THE HELL CAN YO GET ALL THE SIGNALS (POWER,NETWORK,USB'S,VGA,...) FROM A SINGLE PORT?

However, any problem that is on the mainboard is a BIG problem, especially on a laptop, and if you can get this fixed under warranty or apply the money you would spend on a docking station to do so, that would be the better way to go, unless the dock is pretty cheap.[/REFURBISHED DOCKS ARE AVAILABLE ON EBAY AT USD20. THE COURIER TO GET IT IN SPAIN WOULD COST ME MORE THAN THAT...MAYBE THE VGA PORT IS JUST LOOSE, THERE'S NO WAY I WILL SEND IT TO HP SERVICE (GUARANTEE IS EXPIRED ALREADY AND I KNOW THE RESPONSE TIME THEY HAVE) EITHER I WILL TAKE THE RISK TO OPEN IT BY MYSELF OR AT A LOCAL HARDWARE SHOP.

THANKS FOR HELP!

[Nelson37]

Yes, the display gets the same signal from the same source as the VGA port. The external port is an add-on to the main video card, actually the to the mobo itself. Your symptoms not showing up on the display indicate the card itself is OK.

Laptops have a special wide bus connector for the docking station. There is no bandwidth issue. For $20.00 it's probably worth a shot, and cheaper than the USB video card.

It also could be the LG display or the connector on that end. Do you have another PC to do an extended test of the LG itself?

[jagabo]

Your symptoms not showing up on the display indicate the card itself is OK.

I'm not so sure of that. The laptop's LCD display is probably driven off a digital port (DVI) so it doesn't involve the video DAC that's used for the analog VGA output. The problem the OP's having sounds like a DAC issue.

[edDV]

Your symptoms not showing up on the display indicate the card itself is OK.

I'm not so sure of that. The laptop's LCD display is probably driven off a digital port (DVI) so it doesn't involve the video DAC that's used for the analog VGA output. The problem the OP's having sounds like a DAC issue.

I agree and if this chipset supports dual display, the resolution is set separately.

Have we established video is to be displayed? If hardware video decoding isn't needed, the USB2 device should work.

[jeproca]

It's neither the cable nor the LG display. Tried my mac on the display with the same cable and it works fine. Linked the same HP laptop to my TV with a different vga cable and same sh...

Based on this, can we conclude that most probably I have a problem not with the video board itself but with the vga output?

Are sure that the HP Expansion Port 3 gets the vga signal directly from the video card which means that this signal should be ok (provided the video board is not the damaged element)?

[jagabo]

It's neither the cable nor the LG display. Tried my mac on the display with the same cable and it works fine. Linked the same HP laptop to my TV with a different vga cable and same sh...

Based on this, can we conclude that most probably I have a problem not with the video board itself but with the vga output?

The DAC and VGA port are part of the "video board".

Are sure that the HP Expansion Port 3 gets the vga signal directly from the video card which means that this signal should be ok (provided the video board is not the damaged element)?

In all likelihood the VGA signals at the expansion port (and hence from the docking station) are exactly the same VGA signals that are on the laptop's VGA port.

Does the docking station have a DVI or HDMI output? That would bypass the problematic analog VGA section.

[jeproca]

Gosh! Things went worse. Yesterday the image on the display turned from the snowfall effect to 100% white and that's it. Switched off the computer to get the signal back to the laptop screen and have not been able to send any signal to the display screen with the Fn+F4 combination any more.

Image on the laptop screen keeps 100% stable.

What would you do guys?