mid 20011 27'' iMac sudendly doesn't start after GPU fix (reflow)

[nhouse1]

IMAC Mid 2011 27'' (amd radeon hd6970m 1gb)

Hi everyone, I repaired the Imac GPU card by doing a reflow in the oven (typical procedure for fixing that batch of GPUs).

reassembled everything and the problem seemed to be solved. Suddenly, after about a week of proper operation, the computer shut down and now there is no sign of life.
(pressing longer the power button , i changed the power cable, changed the wall socket, tried to remove RAM. Nothing)

I mention this detail: I did not do the reflow myself and who did, removed the GPU from the oven too quickly and two diodes were unsoldered. Then I re-soldered by reflowing again with solder paste . What could have happened?
Could it be just the GPU shorting and not starting the IMAC or something else?
Anyone have any ideas?
Thanks in advance

 

[Fishrrman]

What happened?
Sounds to me like something broke inside -- bad connection, etc.

Looks like you're gonna have to take it apart again, and try again.

If that doesn't work, I suggest that you start looking around for a replacement, new, Apple-refurbished, or used.

 

[Nguyen Duc Hieu]

IMAC Mid 2011 27'' (amd radeon hd6970m 1gb)

Hi everyone, I repaired the Imac GPU card by doing a reflow in the oven (typical procedure for fixing that batch of GPUs).

reassembled everything and the problem seemed to be solved. Suddenly, after about a week of proper operation, the computer shut down and now there is no sign of life.
(pressing longer the power button , i changed the power cable, changed the wall socket, tried to remove RAM. Nothing)

I mention this detail: I did not do the reflow myself and who did, removed the GPU from the oven too quickly and two diodes were unsoldered. Then I re-soldered by reflowing again with solder paste . What could have happened?
Could it be just the GPU shorting and not starting the IMAC or something else?
Anyone have any ideas?
Thanks in advance

Buy another known to be working GPU. It's clearly a hardware issue.

 

[nhouse1]

will do it. maybe i should buy a replacement straight away, maybe i should try to reflow again?
Any advice regarding a known to be working gpu? i wouldn t buy the same model and wait for the same issue to happen again

 

[Fishrrman]

How much money are you going to spend on a 9-year-old Mac, when you're not even sure if replacing the card will fix the problems at hand...?

 

[Nguyen Duc Hieu]

will do it. maybe i should buy a replacement straight away, maybe i should try to reflow again?
Any advice regarding a known to be working gpu? i wouldn t buy the same model and wait for the same issue to happen again

Searching in local market listing. If you are lucky, you may get a working iMac for 25$.
It's all about luck here, if you wish to save money in trade for time.
If you are in a rush, PC parts shops are happy to charge you a heavy premium for that.
I sold my HD 5670m for 45$ after purchasing a WX4150 for 75$.

 

[nhouse1]

just a question: if the gpu has a problem like , let s say, in this case.. shouldn’t the Imac switch on after power up and make any noise? like fan moving or whatever symphtom of life?
because now i just get silence and no response and i just thought that the Imac should make some noise after powering up (at worst, i thought that would make some sort of sounds of other stuff)
do you know about this?

 

[Nguyen Duc Hieu]

just a question: if the gpu has a problem like , let s say, in this case.. shouldn’t the Imac switch on after power up and make any noise? like fan moving or whatever symphtom of life?
because now i just get silence and no response and i just thought that the Imac should make some noise after powering up (at worst, i thought that would make some sort of sounds of other stuff)
do you know about this?

You already opened your iMac.
You can take a look at the 4 troubleshooting LEDs to check for yourself.
Others have given instructions to reset the PRAM after removing the MXM card. Try it to see if it can help.
You can also install the card to a windows PC to see if it can be recognized by the PC.

 

[USB3foriMac]

removed the GPU from the oven too quickly and two diodes were unsoldered.

The baking is done at 200 degC. At that temperature, the solder will not melt for components such as diodes. If diodes came off, the unit likely fell and physical damage occurred.
If the diodes indeed came off by soldering, the temperature was too high, and likely some capacitors and other components got extremely degraded.
I think you'll have to write this card off. There are already suggestions about what you can do, and I would try to keep further investments at a minimum.