iMac power off unexpectedly when using Premiere Pro 2020

[dougngkb]

Hi, I'm having this problem while using Premiere Pro 2019 to 2020. My iMac is 2019 Intel i9, 64GB RAM, Radeon Pro Vega 48. The problem appears about 6 months ago, After contacted apple for a few times, they agree to replace the logic board and the graphic card. But unfortunately, the problem still exist. The only thing I didn't replace are the OWC 64 GB RAM and my external harddrive (G-Raid Thunderbolt 3 20TB). Is there any chance that causing the problem? The strange thing is the iMac only shut down while using PrPro, NOT After Effects, photoshop or FCPX, when the iMac is idle while PrPro app was opened, it didn't unexpectedly shut down. Thanks.

[Jeff Bellune]

You said "while using Premiere Pro" and when "the iMac is idle while PrPro app was opened".

I understand that to mean that if you start Pr and don't do anything in the app and just let it sit idle, everything is fine.

The question is what exactly were you doing when Pr shut down? Were you importing files? Trimming clips? Adding media to the timeline? Exporting? 

Maybe if we can isolate the shutdown to specific activities, we can pinpoint the problem.

[dougngkb]

There's no specific action causing the shut down, sometimes just editing, playing the timeline or clips, sometimes exporting.

[Jeff Bellune]

Okay. Then I recommend stress testing your onboard memory.

I'd also disconnect your external drive and create a new, small Pr test project that only uses media on your internal drive. That would help isolate/eliminate the external drive as the source of the problem.

[dougngkb]

Thanks for the reply. "disconnect your external drive and..." Try that before and it works fine, but I didn't test extensively so I may try again. But I suspected that it isn't the problem of the external HD, as I have another 2015 i7 iMac, I  connected to it and it works fine. Someone on Apple Support Communities recommend an app called "Etrecheck" to help diagnos the problems of Mac computer. Is it trustable? Thanks.

[Ng5E37]

I've tested the app extensively and found out that if I open Premiere, open a project and then switch "Mercury Playback Engine GPU Acceleration (Metal)" to "Mercury Playback Engine Software Only" (Go to File>Project Settings>General>Video Rendering and Playback>Renderer), the shutdown problem was solved. I've used this method for a day's work and no problems found, but if I turn on GPU Acceleration then the iMac will power-off itself in few minutes. About 2 months ago, I had my iMac's logic board replaced due to this problem because I thought there's a faulty graphics card (AMD Radeon Pro Vega 48), but its still happening after the replacement, so I guess that the problems are caused by the AMD Radeon graphics card and Premiere Pro.