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Hardware Thread, VGA splitter cable in Technical; I've ordered a bunch of VGA Y cables for new classrooms only to find out they don't work! The signal ...
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    judyB's Avatar
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    VGA splitter cable

    I've ordered a bunch of VGA Y cables for new classrooms only to find out they don't work! The signal will only go to the projector. Our network manager did a bit of googling and apparently they can't work as the VGA port now polls for information back from the display device, so it can't cope with two signals coming back. Is this right? Is there any way of making them work? I can put up with quality problems - I just want an output.

    I realise powered splitters are a better solution but a lot of the new classrooms don't have spare power sockets (don't ask) which is why we went for the cables. The PCs only have VGA out, so I can't use DVI or anything else. I really don't want extension leads everywhere - anyone got any ideas??

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    Use laptops?

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    judyB (25th June 2010)

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    dgsmith's Avatar
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    I'd go with this. USB powered and works a treat where we are using it (5 classrooms at the moment). Space efficient, no need for power plug, small/compact and no quality loss as it is still powered.

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    Alis_Klar (7th September 2010), BatchFile (28th June 2010), bladedanny (15th February 2011), dhicks (25th June 2010), diggory (25th June 2010), judyB (25th June 2010), laserblazer (25th June 2010)

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    Gurra's Avatar
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    Quote Originally Posted by judyB View Post
    ...apparently they can't work as the VGA port now polls for information back from the display device, so it can't cope with two signals coming back. Is this right? Is there any way of making them work?
    There may be, depending on what graphics card you have. Having said that, I don't have any experience with passive splitters, we only use DVI-I to DVI-A + VGA splitters.
    If this is your issue and you have Intel 900 series or newer graphics (9xx, 3, 4 and 5 series chipsets), the later Intel graphics drivers support hardcoding of display resolution. Then the driver does not use EDID information from your monitor(s). In theory this could fix your isse. But it also depends on how the Y cable is wired. Have you seen it working on any VGA interface?
    /Gurra

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    judyB (25th June 2010)

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    We buy dual head graphics cards for our teacher PCs as it keeps things tidy. I realise this is no help for the current situation.

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    judyB (25th June 2010)

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    enjay's Avatar
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    Can't comment on the polling ports thing, but I can say that we've ditched all our Y-cables for powered splitters (StarTech.com VGA Video Splitter / Distribution Amplifier 2 Port (ST122LGB) - dabs.com) instead - the image is much brighter and doesn't have the ghosting that we got on the cables.

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    Another possibility is using a VGA splitter that uses a PC's PSU and installs into one of the card slots.
    Lindy do some good ones - however they don't fit in half height slots.
    Also certain HP machines (eg. DC7700 tower) where there are slots are slightly obscured by a flange, they won't fit.
    They are powered by the PCs standard power cable.
    Video Splitter - X-VGA, Internal, 2 Port | Video Splitters & Extenders | Sharing, Converting, Extending | LINDY UK

    Splitter Y cables, mean you get less signal power and the problems of reflections from a long cable. You will really need a powered VGA splitter or at least a seperate VGA card.

    I've got some spare internal one's I won't be able to use if you want to try one (or two..)
    Last edited by diggory; 25th June 2010 at 10:53 AM.

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    dgsmith's Avatar
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    Quote Originally Posted by enjay View Post
    Can't comment on the polling ports thing, but I can say that we've ditched all our Y-cables for powered splitters (StarTech.com VGA Video Splitter / Distribution Amplifier 2 Port (ST122LGB) - dabs.com) instead - the image is much brighter and doesn't have the ghosting that we got on the cables.
    We're doing the opposite - ditching the splitter boxes in favour of the startech USB-powered splitter I linked above. A little cheaper than a PCI card and a splitter box but from what I can tell quality is just as good. Before these we tried just a basic y-cable with no power at all and did find the quality was inadequate.
    Last edited by dgsmith; 25th June 2010 at 11:01 AM.

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    Yeah, we always go with powered splitters. We've never tried the dual output graphics cards but I'd like to sometime. However though a few of our machines have used and some may still be using splitter cables and they work although like people have said the image is ghosted, distorted and generally awful.

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    enjay's Avatar
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    Quote Originally Posted by dgsmith View Post
    We're doing the opposite - ditching the splitter boxes in favour of the startech USB-powered splitter I linked above.
    So long as it is powered, I think that's all that really matters. I had missed your earlier post, but I do like the product you link. It is powered which gets round the quality/brightness issue, but saves on plugs. I'll buy those in future, thanks!

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    judyB's Avatar
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    Thanks all for your help - 1 hour of edugeeking = about 10 hours worth of googling!

    I've used Y cables for a while and never really had a problem, apart from the odd ghosting issue - which as it's on the monitor teacher's don't mind, as they don't look at it much, especially if they have an IWB. In fact given that the new rooms all have IWBs we did consider ditching the monitors altogether!

    I've decided to go for the USB powered splitter- very neat solution. I looked into turning off the DDR/EDID information coming back from the monitor - it's an Intel i5 chipset and even though it lets you set a custom resolution it won't ignore the EDID info.

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    Little-Miss's Avatar
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    ....so glad i only bought the one!!

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    Here is an interesting low tech idea especially if you have a cheap expendable y adapter. Simply snap off the moniter id pins on the PC end on one of the Cables and see if it still works but outputs to both. Be careful though to force the computer to use a resolution and refresh rate that is supported by both the projector and moniter so there is no chance of damagine either.

    http://en.wikipedia.org/wiki/VGA_connector

    In the long term the powered adapters are a better idea but this method may work too.

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    enjay's Avatar
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    Just found these USB-to-VGA converters too - Startech USB to VGA Multi Monitor External Video Adapter | Ebuyer.com I haven't tried them, so I don't know what the quality is like, but they could presumably be used to set different resolutions on the two monitors, which all the other splitters we've mentioned so far don't.

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    Powered Splitters vs Dual Head graphics

    It's all a question of cost. Sometimes it can be cheaper to add an external low cost dual head graphics card than to buy an external powered splitter due to the price of the latter. The advantage then is that you can then use both mirroring and extended desktop modes.
    With extended desktop you have the advantage of teachers being able to show a video on the projector while working on something else on the screen. Then again, it adds a level of technical complexity for the teachers so it's not for everyone.
    Again, if you have a newer Intel chipset, and if you're lucky and your computer vendor has got their system BIOS configured correctly you can save even more by using an ADD2 card such as this one: Low Profile Silicon Image Orion ADD2-N DVI add-in Card on eBay (end time 27-Jun-10 21:43:57 BST).
    The ADD2 cards take advantage of the fact that most if not all Intel chipsets are dual head, and simply convert the secondary digital video interface signals in the PEG interface to DVI using a cheap video transmitter. VGA versions are available but they are more uncommon and require more expensive components to build.

  20. Thanks to Gurra from:

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