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Windows 7: DVI to VGA adapter - useless? - wrong pins?

04 Jan 2012   #1
hucker

Windows 7 Ultimate x64
 
 
DVI to VGA adapter - useless? - wrong pins?



This does not work. The pins round the long pin on the DVI side are missing, so how can an analog signal possibly get to the VGA side? The vendor sent me another set with the extra 4 pins and they work fine, but I'm interested to know why these ones were ever made like this!

Wikipedia article - see pins C1 to C4


My System SpecsSystem Spec
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04 Jan 2012   #2
niemiro

Vista Home Premium x86 SP2
 
 

Hello!

As a starting point, so we are on the same playing field, do you understand the difference between DVI-A, DVI-D, and DVI-I, all the difference between single link and duel link? You can read about them here: All About DVI

What you are showing in your picture is a DVI-D Dual Link to VGA adapter. This adapter will take in a digital DVI input, convert, and output it to VGA, and so will be only that way around.

What exactly were you trying to do? With a few conversion cables, and with some difficulty, it is possible to connect a VGA graphics card to a DVI monitor, although my understanding of this is that it cannot work.

Richard
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04 Jan 2012   #3
hucker

Windows 7 Ultimate x64
 
 

Quote   Quote: Originally Posted by niemiro View Post
Hello!

As a starting point, so we are on the same playing field, do you understand the difference between DVI-A, DVI-D, and DVI-I, all the difference between single link and duel link? You can read about them here: All About DVI

What you are showing in your picture is a DVI-D Dual Link to VGA adapter. This adapter will take in a digital DVI input, convert, and output it to VGA, and so will be only that way around.

What exactly were you trying to do? With a few conversion cables, and with some difficulty, it is possible to connect a VGA graphics card to a DVI monitor, although my understanding of this is that it cannot work.

Richard
I am plugging an analog monitor into a digital graphics card, not the other way round.

I understand all the various digital and analog connections on the socket. But I don't believe there is a DAC chip in this - it was under a quid. And it doesn't do the conversion as there is no analog signal produced!

Normally I get something that looks precisely like the picture, except it has 4 pins around the large one - the analog pins. I've never come across a graphics card without analog on the DVI socket (except one which had it on only one of the two DVI sockets).
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29 Jun 2012   #4
AAnnddyy

Windows 7 64bit
 
 

Hi,

did you ever work out what this adapter was for? I have the same one and assumed the graphics card didn't output analog signals but when I looked at the DVI connector like yourself it was missing the pins! google search came up with this post and not much else.

My guess is the manufacturers made a mistake and wired up the digital rgb pins not really knowing what they were doing and not testing it, that's what you get with cheap china electronics sometimes. Might cut it open and have a look as it's useless as is
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30 Jun 2012   #5
hucker

Windows 7 Ultimate x64
 
 

I never found out, I threw them away. I should have looked inside as I'm normally inquisitive like you. Please let me know what you find in there!
My System SpecsSystem Spec
30 Jun 2012   #6
AAnnddyy

Windows 7 64bit
 
 

It was really strange, Can't see what they were trying to do.

There were 6 connections:

On the VGA side the pins 6,7,8 (R,G,B Grounds) were shorted and connected to the correct analog ground of the DVI

On the VGA side pins 1,2,3 (R,G,B) looked like they connected with pins 6,7,8 of the DVI (DDC Clock, DDC Data, Analog vertical sync)

On the VGA side pins 13,14 (Horiz and Vert Sync) looked like they connected with pins 23,24 of the DVI (TMDS Clock+, TMDS Clock-)

So go figure! the pins of the VGA port are actually related to the correct pins, at least the very minimum required to get a picture; but other than the analog ground, the pins of the DVI are seemingly random?

*New connector bought on Ebay, checked the pins in the photo this time
My System SpecsSystem Spec
30 Jun 2012   #7
hucker

Windows 7 Ultimate x64
 
 

Maybe someone was looking at the wrong side when they were wiring it up and inverted the pin numbers?

I complained to my Ebay seller telling him about the missing analog pins, and he apologised and sent me some correct ones (I had bought 10!), and a free gift of a couple of mini camera tripods as he only had 7 replacements.
My System SpecsSystem Spec
30 Jun 2012   #8
hucker

Windows 7 Ultimate x64
 
 

I've seen worse on Ebay form Hong Kong - someone trying to sell a molex to 6 pin pci express power adaptor, which was wired in such a way as it would short the 5 volt line with the 12 volt line. I tried to explain to them that they were going to end up breaking computers, but they wouldn't listen, neither would Ebay. I suppose when someone's computer blows up they are unable to leave bad feedback :-/
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 DVI to VGA adapter - useless? - wrong pins?




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