iMac in the oven at 390°, now it won't turn on.

[ActionJacksonHern]

I have a iMac 2011 27", EMC 2429, 2.7GHz, MC813LL/A, and I'm having problems. First one was the display shutting down randomly, likely due to the common problem with this iMac that Apple did recall here. After days of research, I found the most common fix (after the recall expired) was to actually take the faulty GPU and bake in the oven. Many articles and YouTube videos available here. Apparently almost every person that tried this got it working. So I did the same, baked at 390°F for 10 minutes.

Problem is, once I put back in the baked GPU and everything back together, the iMac won't fully power on. I hear the fans run for about 0.5 seconds then shut down. I opened the iMac again to look at the diagnostic LEDs (here). The first one is always illuminated, implying that "trickle voltage from the power supply unit (PSU) has been detected by main logic board, the power supply is functioning, and LED will remain illuminated while iMac is plugged in." But as I try to power on the iMac, the second LED will flash on for that same 0.5 seconds as the fans power, but then turn everything off. It will repeat this cycle every 5 seconds. Start up loop.

I've reset the SMC (here) on the iMac by unplugging, holding the power button for 5 seconds, release, plug in, then power on. Only difference was the fans stayed on about 0.2 seconds longer now, but still went into that power up loop.

I can't see if the 'baking the GPU' actually worked for me because the iMac won't get to the stage of turning on the LCD display, which would also be signified by the 3rd and 4th LED.

I feel it is a short or something wrong with the PSU. It's giving some power, but unable to give enough for full start-up. It was working before I did the GPU teardown, so I'm wondering if I shorted something in the teardown. Some people have mentioned a fuse here, haven't found it. I also have not tried taking a blow dryer to the PCU yet (here), as some have suggested. Any ideas?

 

[Razzerman]

Hello there,

The 'normal' symptoms for a failing graphics card on these imac are vertical stripes, distortion etc. I'd suggest that the whole screen going off could be a different issue. No harm in doing the reflow, and your time & temps look fine.

It might be worth looking at this thread about the backlight inverter - https://www.ifixit.com/Answers/View/106622/Backlight+turning+off,+inverter-board+changed

I'd vote for 'some other symptom'

Cheers,

Razzerman

 

[ActionJacksonHern]

Hello there,

The 'normal' symptoms for a failing graphics card on these imac are vertical stripes, distortion etc. I'd suggest that the whole screen going off could be a different issue. No harm in doing the reflow, and your time & temps look fine.

It might be worth looking at this thread about the backlight inverter - https://www.ifixit.com/Answers/View/106622/Backlight+turning+off,+inverter-board+changed

I'd vote for 'some other symptom'

Cheers,

Razzerman

From the internal Apple note on the GPU issues this iMac had, one of them were commonly black screens. I also tried two different functioning inverters and that was not the issue. Thanks for the ideas though.

 

[philosoraptor1]

For a moist, tender iMac, always bake at 375 for no more than 7 minutes. Lesson learned.

 

[Fishrrman]

I guess you over-baked it.
Time for a new iMac.

 

[snoopyonline78]

I guess you over-baked it.
Time for a new iMac.

do you mean the whole mac is now broken, or can i bought a new gpu ant it works again?

 

[T'hain Esh Kelch]

Hello there,

The 'normal' symptoms for a failing graphics card on these imac are vertical stripes, distortion etc. I'd suggest that the whole screen going off could be a different issue. No harm in doing the reflow, and your time & temps look fine.

My failing 6970M resulted in random restarts and shutdowns. Didn't get visual artifacts until it started failing 6 months after my third oven bake. The GPU finally died after the fifth bake, but I got two more years out of it just by going with the oven, so I am happy.

My 2011 iMac runs fine with the dead GPU, I just don't have a working screen. It can be accessed just fine over LAN.

 

[Nguyen Duc Hieu]

My failing 6970M resulted in random restarts and shutdowns. Didn't get visual artifacts until it started failing 6 months after my third oven bake. The GPU finally died after the fifth bake, but I got two more years out of it just by going with the oven, so I am happy.

My 2011 iMac runs fine with the dead GPU, I just don't have a working screen. It can be accessed just fine over LAN.

Your iMAC is compatible with PC GPU for an upgrade. I suggest nVidia Quadro K2100M.
Flash GPU BIOS for the best result.

 

[T'hain Esh Kelch]

Your iMAC is compatible with PC GPU for an upgrade. I suggest nVidia Quadro K2100M.
Flash GPU BIOS for the best result.

Yeah, I am following the GPU upgrade thread carefully. But getting a GPU for a 9 year old machine is pretty expensive, and I am not in any way geared to flash it myself.

 

[r6mile]

You can get a K610M for $30 on Aliexpress, and the flashing is pretty easy using the Linux USB method described in the thread. Don't be discouraged!

 

[dapa0s]

Actually you could have just put the GPU in a regular toaster, on a high setting, of course. That tends to work better.

Just don't forget to rinse it out and cool it with water afterward.

 

[Nguyen Duc Hieu]

Yeah, I am following the GPU upgrade thread carefully. But getting a GPU for a 9 year old machine is pretty expensive, and I am not in any way geared to flash it myself.

You don't have to do it yourself if you can go to the shop which sells it. Normally these cards are ripped off a laptop, you can ask them to flash it for you, while it still inside the laptop. Where I live, when we go buy 2nd parts, we always visit the seller's place and test them to ensure they are in working order, it's pretty easy to do the flashing right there.

 

[T'hain Esh Kelch]

You don't have to do it yourself if you can go to the shop which sells it. Normally these cards are ripped off a laptop, you can ask them to flash it for you, while it still inside the laptop. Where I live, when we go buy 2nd parts, we always visit the seller's place and test them to ensure they are in working order, it's pretty easy to do the flashing right there.

Cards like that are almost never sold in my country, unfortunately. But lets keep the thread on track after this post!

 

[Nguyen Duc Hieu]

Cards like that are almost never sold in my country, unfortunately. But lets keep the thread on track after this post!

There are some cheap solutions for us amateurs:
1. Small PCs which can accommodate an MXM card:
Like the HP Compaq 8200 Elite USDT

2. MXM to PCIe adapter

3. And, if you can open your iMac and run multi OS on it, you may install the card and use Windows to flash it. At first there would be some issues with the unflashed card, but they would go after a successful flash.