Which part of a graphics card is most likely to have failed when there is no video output?

[Nuke Dukem]

To elaborate on the title: when a port gives you no output, or when it is half-working, for example. Display and/or cable being ruled out as working.

Context: Bought a second hand GTX 660 last year, which only outputs VGA signal through the DVI-I port via an adapter. HDMI fails (I got it working only once, by accident), and DisplaPort, as far as I was told, fails too - can't test it, don't have DP hardware at my disposal, have yet to use it for the first time. More recently, a friend bought an old AGP X1650 to replace one that died, and complained that DVI output won't work. I investigated, tried the DVI-VGA adapter - it works, same as with my card.

This got me thinking. What's the most common problem for a card to fail to output? Would it be:
a) the female sockets on the back of the card losing contact with PCB, corroding or in any other way failing physically?
b) some special circuitry assisting the GPU with video output that has become fried chicken? (talking out of my ass here, don't know how it's done exactly)
c) the display interface on the GPU failing only by itself?
d) something else?

Also, could there be such a thing as "digital only" fails where only the analog VGA is working, but no digital outputs, regardless of standard?

Most of the time, people say "Oh, this thing doesn't work" and leave it at that, without any thought as to why or where the actual problem is. But I'd love some details on this

 

[Malik Sajid]

All possibilities exist. It's hard to tell without examine the card physically. But since all the sockets usually are exposed to the same conditions and one of them is still working I'd rule out losing the contact with the PCB. HDMI and DP are hollow compared to VGA and DVI so most likely the card was working in a high moisture environment and the contact pins get corroded maybe you can try to clean them with some isopropyl wipes or a contact cleaner spray

 

[SoNic67]

Does the the monitor supports the HDCP encryption required for HDMI/DP? VGA doesn't have that limitation.

More about HDCP:
https://en.wikipedia.org/wiki/High-bandwidth_Digital_Content_Protection

PS: The analog conversion for the VGA output, in the 6xx generation of nvidia cards it is done by a separated DAC chip, from one of the available digital outputs of the GPU, so that's obvious that digital output works. That DAC has it's own HDCP keys. VGA doesn't "exit" directly from the GPU.

 

[dorsetknob]

b) some special circuitry assisting the GPU with video output that has become fried chicken? (talking out of my ass here, don't know how it's done exactly)

What your describing here is "The Pixel pump Failing" ( a comment worthy of "talking out of my ass here")

 

[Gorstak]

I think gremlins overwrite the bios and make cards die or work quirky...not just cards, mobos too...you should use msi mobo, which requires encrypted signature to allow bios update, and integrated gpu, either intel iris series or amd r7 and better if you wish to play games...or, find some means to protect yourself from gremlins, but I have yet to find that way...

 

[Nuke Dukem]

maybe you can try to clean them with some isopropyl wipes or a contact cleaner spray

I've never had to do that to a card, didn't cross my mind. Thanks, I'll try that.

Does the the monitor supports the HDCP encryption required for HDMI/DP?

Well, my monitor certainly supports it, and the TV that the card managed to display HDMI signal on that one time is some obscure chinese brand, so I don't think it's that. But thanks for the idea.

What your describing here is "The Pixel pump Failing" ( a comment worthy of "talking out of my ass here")

Sarcasm detector broken today. Can't tell if laughing with me or at me.

I think gremlins overwrite the bios and make cards die or work quirky...not just cards, mobos too...you should use msi mobo, which requires encrypted signature to allow bios update, and integrated gpu, either intel iris series or amd r7 and better if you wish to play games...or, find some means to protect yourself from gremlins, but I have yet to find that way...

Last time I saw gremlins was the last time I opened my case to clean it - one of 'em was chewing on my DVD's SATA cable, another was spinning along with the CPU fan, and a third was sitting quietly in a corner in the bottom, taking a piss. Not unlike what you did with your comment.

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My original idea wasn't "Please help me fix my card!", but rather to get some impression, stats and stories from your own experiences. But thanks for the ideas anyway

 

[Gorstak]

I think I found something that helps appease the gods and turn at least the noob gremlins away: turning off workstation and server service.