Good morning everyone. I'm Italian so sorry for my english.

Yesterday was in trouble. I am a video operator and I was at the theater, connecting my American Macbook Pro Retina Late 2013 (macOS Mojave) with a Thunderbolt / VGA third-party adapter. The VGA cable was about 20 meters long and was connected to a plasma screen that had only the vga as a connection. When I connected the cable in question the mac turned black for a second (as if it had recognized it) but then it didn't really work (in the display settings the second screen wasn't really visible). Here's what I did to try to solve the problem:

  • Restart the MAC with the cable and adapter connected
  • Reset SMC and NVRAM
  • Used another thunderbolt / VGA adapter
  • Started in safe mode

None of this worked and also connected my adapter with the same cable and monitor to another Mac belonging to another person next to me and it worked. Just to make things even more mysterious, I returned home and tried my VGA monitor with my VGA cable to the mac with the same adapter and everything works great. Do you have suggestions? ps: The monitor that didn't work on my computer I don't think it supported a resolution higher than 1024x768, and i've wrote that mac comes from USA because yesterday I was in Italy (can this is a problem for video protocol?)

1 Answer 1


I've solved problem buying a original adapter apple thunderbolt/vga. I still can't understand why my mac not works with compatibile adapter only with long vga (with short vga cable works with compatibile adapter as well) cable (20mt) while the others mac works with it.


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