No signal on Monitor

OK, is your display wider than 1920 wide? if 1920 wide or less, you could buy a Mini DisplayPort to DVI adapter (Single-Link, good for uptown 1920 wide) and try the Mini DisplayPort output with that adapter. They are not very expensive.

If wider than 1920 wide, the adapters to Dual-Link DVI alone are over US$100, so try replacing the card.

I have exactly the same problem with my 2008 Mac Pro 3.1 Suddenly, for no reason, the graphics card has evidently stopped working. Tried more than one monitor and both video ports. same result - no signal.

I had a VERY long chat with Apple Support just now (with someone who had absolutely no idea of where in the world Scotland is) and the only suggestion was to either take it to my nearest authorised service provider (which is a seven hour drive away) or to find a refurbished graphics card.

Frustratingly, I was told that Apple Stores (my nearest one is only a 40 minute drive) will not look at it because it's an obsolete product.

Good luck - it sounds like (like me), you're gonna need it!

The most likely failure is the high-Voltage portion of the graphics card.

What interface are you using to talk to that display? If only that interface failed, is there a way to use an adapter to get it to work using a different display-interface?

Sorry if I'm being easily confused, but I don't really understand why you are suggesting using adaptors? The Mac Pro and these monitors were working absolutely fine together until a couple of weeks ago, then it's as if the video ports simply stopped working.

I'm not sure how I can get a replacement video card for a 14 year old Mac, short of scouring the world for refurbished ones? I want to replace it anyway, it's just the short-term need to see the HDD while I populate its replacement.

Hi Robin, even the best of us, likeGrant, fall off the track once in awhile or don't reread everything that has [assed. :)

Luckily we have one of the Only Macs you can actually get graphic cards for...

https://everymac.com/systems/apple/mac_pro/faq/mac-pro-default-graphics-cards-dvi-dual-link-mini-displayport.html

https://bizon-tech.com/macpro-graphics

https://www.ebay.com/b/Mac-Pro-Graphics-Card/27386/bn_7023356896

If your card has no Mini DisplayPort, then what I wrote can not apply to you. If the other DVI does not work, the card has completely failed.

For certain modern cards with multiple outputs, you may be able to just bypass the broken display generator and get that same card working with a cheap adapter.

I have a 4870 card where the direct output to my Legacy display has died. When I used an adapter from Mini DisplayPort instead, it connects with a different display-generator in the card, and everything works fine. (the cards have multiple independent display-generators/rasterizers to support multiple displays at the same time).

Hi Grant. I'm either being really thick here (most likely) or we have been talking at cross-purposes.

When you have been speaking about an 'adapter', I assumed you meant something that plugs into one of the DVI ports to change it to a different form of connection? I didn't understand how this could help, as neither of the DVI ports appears to be working.

The video output on my early 2008 Mac Pro is the original card, outputs, whatever... which has two DVI ports. Both of these have suddenly stopped working, leading me to assume that the video card has failed.

Please can we go back to square one and start again, preferably if you could explain your thoughts in simple terms for someone who has no technical knowledge of Mac video output whatsoever? ;-)

Many thanks.

Robin Johnson wrote:

...

neither of the DVI ports appears to be working.

The original Poster said they has a 4870 card, which has a Mini DisplayPort as well as a DVI port.

If your card has two DVI ports, neither of which are working, your card has failed, and you need a new display card.

Whew, that's a tough one to tell, but it seems so , did you have Screen Sharing enabled on it?

I have the same exact thing happening

Also to my 2009 mac pro, stange

In my case I'm using the DVI ports to DVI monitors, no interface being used. Unless I've misunderstood the question?

Thanks. The OP seems to have vanished, but I'm still having poblems so I appreciate the help from you and BDAqua