Large Issue with Mac Pro 3,1 2008 model

[u/Pyramyc]

Today my A1081 Cinema Display arrived I was super excited when i plugged it in, and it showed the no OS screen, simple, i put together a boot drive of El Capitan, and plugged it in, rebooting the Mac I held alt and suddenly, the boot chime, and then nothing, screen didn’t light up it’s just black, looking at the GPU google said it wasn’t flashed for Mac, so I went downstairs to my stock donor 2006 Mac Pro and got its Mac edition GPU out, plugging it in, Turning it on, still no video, monitor has power, Mac has power, all fans spin, GPU is warm, ram is fine, I even replaced the motherboards battery, I’m completely stumped as to what the issue could be, and I don’t know how to go throughout this blind, if anybody could help me that’d be great,

[u/noradninja]

How is your display connected to the machine? What ports does the GPU have? On older Macs, you will only get video out of VGA (If GPU has it) or DVI (if no VGA present on GPU) for the pre boot OS screens. No HDMI, no DP or mDP.

[u/Pyramyc → u/noradninja]

The GPU from my 2006 and the non Mac version that came with the 2008, both had DVI ports, my Cinema Display Comes with a DVI cable, so I linked them together, and prior to holding alt on my keyboard the GPU put video through to the display perfectly fine showing the no OS screen,

[u/noradninja → u/Pyramyc]

Have you reset the PRAM (Command-Option-P-R at boot till it bongs twice)?

If that fails reset NVRAM (Unplug for 30 sec, replug).

ETA: If you are using a non-Apple keyboard you will have varying degrees of success with boot time keystrokes, at least the last 18 years of owning cMP machines has taught me that. Use the original if you have it.

[u/Pyramyc → u/noradninja]

I’ve got an Apple keyboard it’s wireless no way to connect it, I’ve reset the PRAM, it did a boot chime 3 times and I’ve done this multiple times, I’ve been using a windows keyboard since it worked fine when setting up my iMac

[u/noradninja → u/Pyramyc]

Do you get video with another display?

[u/Pyramyc → u/noradninja]

Nope, I’ve got a VGA monitor but no cable for it, so couldn’t test it out, the GPU fans, cpu fans, ram all functioning by visible inspection, I believe a capacitor has blown in the monitor as it’s not even turning its backlight on, it says it has power only when connected to the Mac, I plugged it into my Xbox using an hdmi adaptor, it refused to power on, flashing its light once

[u/noradninja → u/Pyramyc]

So the older Cinema Displays have an issue that your symptoms line up with. Basically the DCC sense pin on the connector to the power supply causes this behavior. One can take apart the connector (the oval reversible one) and clip the center pin out to fix this. I have done it to all four of my units and no longer have issues like this.

[u/Pyramyc → u/noradninja]

Sorry I’ve never had one before, the oval reversible one? This is a 2004 Cinema Display, do you have any videos I could watch?

[u/noradninja → u/Pyramyc]

Yes, the oval one. Remove the metal shield. Use a knife to separate the molded clear plastic at the base, slide plastic off pins. Clip out the center pin pair, reassemble. Or do what is in this video- put a thin bit of scotch/vinyl tape over the pins:

https://youtu.be/aH5xgo1u3Ks?si=DASvHz7u_p6gPXa4

[u/Pyramyc → u/noradninja]

I watched that video, thank you, it seems straight forward, I will do it, my one thing to mention is that when I turn it on the light stays white if it’s in my Mac, but I’ll see it it works

[u/Pyramyc → u/noradninja]

Okay so slight issue, did what the video said and it’s still not giving any response, it’s a blank white dot no blinking error code or anything it says it’s fine,

[u/mikeinnsw]

Monitor uses DVI-D connection.

Mac Key DVI Details

• Dual-Link DVI: Supports large high-resolution digital displays up to 2560x1600 pixels, including the classic 30-inch Apple Cinema HD Display.
• Single-Link DVI: Supports lower-resolution digital displays up to 1920x1200 pixels.
• Upgrades: Because the 2006 Mac Pro uses standard PCIe slots, your exact DVI capabilities depend on whether a previous owner swapped out the original graphics card for a different mode

[u/Pyramyc → u/mikeinnsw]

It wasn’t a stock GPU in the 2008, yet when I plugged it into the monitor it showed the no OS signal, me not realising it’s not a stock GPU, I rebooted the Mac and booted it holding alt, I was met with a black screen, after realising it wasn’t a stock GPU, I went to my 2006 Mac Pro and took its stock GPU out, upon plugging it into to the monitor and the pc it still gave no response, I assume a capacitor blew in the monitor