Need help with this VGA connection (pics) - AVS Forum
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post #1 of 8 Old 12-25-2006, 06:34 PM - Thread Starter
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I have this DVR that has an (optional) VGA output, but did not come with the little ribbon cable connector that goes from the mainboard to the vacant D15 VGA connector slot at the back face of the unit. Please see pics.

Having trouble locating the original seller dude to acquire the cable. Wonder if you guys might know how I should make this connection to be able to connect a VGA monitor.

The empty black connector is labelled 'VGA' on the circuit board. I have a 20-pin ribbon cable, but not sure about the pinout. Is this a common cable I can just buy? Or is it something I can solder together.

p.s. I don't have the mainboard schematic. Just what you see in the pics.
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post #2 of 8 Old 12-25-2006, 06:38 PM - Thread Starter
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also, the manual has this pic of the D15 VGA pinout, which helps me a lot.
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post #3 of 8 Old 12-28-2006, 11:32 AM
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Quote:
Originally Posted by Gaze
also, the manual has this pic of the D15 VGA pinout, which helps me a lot.
Actually, the VGA pinout is like in the attached picture.
You can determine the ground(s) by using an ohm-meter and measure between the screw just above the connector an the pins.. from there on you can make some calculated guesses..
I would assume this connector is designed to be 1 on 1 (could be all mingled up as well, don't shoot me)

give it a go..
LL
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post #4 of 8 Old 12-28-2006, 05:52 PM - Thread Starter
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Hey, thanks for the help! :cool:

I believe I've I determined all the grounds. 9 of them.

I compared the remaining pin voltages to another (known) vga output on a differenct board. I have some guesses, but still not quite sure.

At this point I'm digging for more info about the pinout. Gonna try another known vga source for more comparisons.

Could I fry something taking guesses here, ya think?
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post #5 of 8 Old 12-28-2006, 07:03 PM
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Be a little careful here, because an incorrect connection could fry the display you attach.

If you knew for a fact that a flat ribbon cable is being used, and that the d-sub is a dual row type (ex. serial port 5+4 pin), then it might be worth a try to make up a cable with IDC (insulation displacement type) connectors.

But I wouldn't try that because of two things:

1. I've never bumped into a 3 row (5+5+5 pin) d-sub IDC connector. They may exist, but I've never seen them in an electronics parts store.

2. The black connector on the motherboard is 20 pin, but the closest pin mapping to VGA would be a 16 pin connector.

To summarize, I wouldn't do this without a pin description for the motherboard connector.
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post #6 of 8 Old 12-28-2006, 11:38 PM - Thread Starter
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dbc, thanks for the reply.

Yeah, it's weird how the header connector on the board is 20-pin feeding a 15-pin D-sub at the rear of the case. I have the 15-pin, 3-row (5+5+5) connector from the elec. store (like shown in attached pics @ the 2nd and 3rd posts) and a 20-wire flat cable that fits exactly into the 20-pin board connector.

But, as you say, I don't want to fry my monitor guessing what goes where. Which is why I'm asking for help from you guys who know way more about this stuff than I do. Come to think of it, I do have an old monitor somewhere I can use as a guniea pig before I try the real thing.

Any more ideas how I might decipher this, by taking voltage measurements or other method?
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post #7 of 8 Old 12-29-2006, 09:22 PM
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I'm not familiar with the VGA signals themselves, but I would imagine that you would need at least an oscilloscope to help identify them. A multimeter would be of little use since most of the signals vary with time. Some kind of test pattern would also likely help.

This out-strips any of my experience. You'll have to rely on someone who has dealt with this kind of area before if you want any solid answers. Good luck to you.
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post #8 of 8 Old 12-30-2006, 09:24 AM - Thread Starter
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I came across a cctv forum. I'll try and post there for additional input. Somebody else in the world must have this (optional) vga output hooked up. Weird how there are really no brand names or markings on the PCB to clue me in where to start looking.

Hey, thanks for your time. Very much appreciated :cool:

Anyone else that can chime in with help...I'm all ears.
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