2011 gpu help please

[Corey Tate]

I need help please before I go insane.

iMac 2011 27”

initial issue: white screen and after some troubleshooting determined GPU failed

1. Replaced with new nvidea k4100m Goulston. Black screen, led 1 and 2 on however no led 3. After days of troubleshooting And assumed I screwed up the Heatsink mod

2. Ordered new k4100m,modified heat sink and ensured nothing touched chips. Same result black screen with first two leds but no 3

3. ordered motherboard and cpu. K4100m GPU still had black screen (leds 1 and 2 only)

4. Assumed bios needed to be flashed so tried the blind bios Nvflash method (by xanderon) to no avail. To make sure I Checked the usb boot on another iMac and everything worked as advertised.

5.Ordered gtx 780 and now here I sit with two new logic boards, three gpu’s, a black screen and only leds 1 and 2 on.

I am at a loss. Please help

 

[Nguyen Duc Hieu]

I need help please before I go insane.

iMac 2011 27”

initial issue: white screen and after some troubleshooting determined GPU failed

1. Replaced with new nvidea k4100m Goulston. Black screen, led 1 and 2 on however no led 3. After days of troubleshooting And assumed I screwed up the Heatsink mod

2. Ordered new k4100m,modified heat sink and ensured nothing touched chips. Same result black screen with first two leds but no 3

3. ordered motherboard and cpu. K4100m GPU still had black screen (leds 1 and 2 only)

4. Assumed bios needed to be flashed so tried the blind bios Nvflash method (by xanderon) to no avail. To make sure I Checked the usb boot on another iMac and everything worked as advertised.

5.Ordered gtx 780 and now here I sit with two new logic boards, three gpu’s, a black screen and only leds 1 and 2 on.

I am at a loss. Please help

1. The first thing you need to order, is a known-to-be-good Mac GPU (say, HD5670m), to check that other iMac components (LCD, eDP cable) are in working order.
2. The second thing you need to order, is a PC/or a mainboard/MXM adapter that has MXM slot, to ensure that the GPU you purchased are in working order. This can be used as the flashing device, too.

 

[Corey Tate]

Thanks for the reply.
re: 1. If LED 3 is not on, what are possible causes? Could the bios cause that?

2. ok I found a MXM to pci-e for cheap. I’ll Check the cards (and flash bios) as you suggested

 

[Nguyen Duc Hieu]

Thanks for the reply.
re: 1. If LED 3 is not on, what are possible causes? Could the bios cause that?

2. ok I found a MXM to pci-e for cheap. I’ll Check the cards (and flash bios) as you suggested

LED 3 ON indicates that the logic board is communicating with the MXM card.
Non-compatible or bad MXM card will cause LED 3 OFF.

 

[Corey Tate]

LED 3 ON indicates that the logic board is communicating with the MXM card.
Non-compatible or bad MXM card will cause LED 3 OFF.

Ok, the gtx780m is working in a dell. I flashed the bios and used the bios provided in Nikey22’s post.

I reinstalled into my iMac and at last the led 3 (logic board) came on. However when I put the screen back on and booted up. I get the white screen of death.
I have tried all the tricks to resolve this but I can’t get past a white screen.
Pressing option doesn’t get me to a boot select screen. Can’t boot to safe mode, Pressing cmd+option+r+o Does force the computer to restart however after chime the screen stays white.
I’m at a loss.

 

[BeatCrazy]

Ok, the gtx780m is working in a dell. I flashed the bios and used the bios provided in Nikey22’s post.

I reinstalled into my iMac and at last the led 3 (logic board) came on. However when I put the screen back on and booted up. I get the white screen of death.
I have tried all the tricks to resolve this but I can’t get past a white screen.
Pressing option doesn’t get me to a boot select screen. Can’t boot to safe mode, Pressing cmd+option+r+o Does force the computer to restart however after chime the screen stays white.
I’m at a loss.

How did you flash the GTX780M bios? Via USB? You may be out of options, other than putting an Apple OEM card in there, get it booted, then start trying different cards one by one.

 

[Corey Tate]

How did you flash the GTX780M bios? Via USB? You may be out of options, other than putting an Apple OEM card in there, get it booted, then start trying different cards one by one.

Ch431a chip programmer

I was afraid of that. Thanks for the help

 

[BeatCrazy]

Ch431a chip programmer

I was afraid of that. Thanks for the help

Possibly the VBIOS didn't take/work, via the chip programmer? Hoping you can find an OEM card to stick I there temporarily to at least get it booted.

 

[Nguyen Duc Hieu]

Another thing to try is the Catalina SD.
Or external monitor connected to the mini display port, if you have a spare one laying around.
You already got the logic board to recognized the MXM card. This mean the flashed Vbios has worked.
Instead of black screen, white screen is a good sign.