Curious Cable Issue

[kitjv]

Although the title above might be interpreted as a hardware issue, my question stem from upgrading to Catalina. Since upgrading to Catalina, I have been trying to resolve an issue of the screen on my secondary display "going black" after a computer restart or the display being disconnected from the computer. But I'm working with Apple Support on this.

But my question is related to the DVI-to-Thunderbolt cable connecting the secondary display to my iMac27. I replaced the cable in an effort to see if the black-screen problem was the result of a faulty cable. With the new cable connected, the secondary display would momentarily work fine for about 5 seconds; then default to a bright white, pixelated screen. Why would the screen remain black with one cable connected; and white & pixelated with the other cable?

Thank you for any thoughts.

 

[Cory Cooper]

Hello and welcome.

I have seen issues like this previously, and if you have tried multiple adapters, then the issue lies with the external display.

-What brand/model are the adapters?
-What brand/model is the secondary display?

C

 

[kitjv]

Hello and welcome.

I have seen issues like this previously, and if you have tried multiple adapters, then the issue lies with the external display.

-What brand/model are the adapters?
-What brand/model is the secondary display?

C

The adapters are Belinda Thunderbolt -to-DVI. The display is an NEC MultiSync P221W.

FYI, I connected the external display to another Mac (MacBook Pro) & it worked perfectly. I could not get it to fail. So at this point I am thinking that the issue lies either with Catalina or the adapter (which itself might not be compatible with Catalina). If that makes any sense.

Kit

 

[Cory Cooper]

OK, thanks.

Yes, that makes perfect sense. It could be an issue with Catalina or the adapter.

I believe that display is about 7 years old, correct. I am not familiar with Belinda adapters.
Which model iMac?

C

 

[kitjv]

Yes, the display is about 7 years old. The iMac is a 27" Retina 5K 2017.

I might add that Apple Support has sent a diagnostic log to engineering. Hopefully I will get some additional info.

Thank you, Cory, for your interest.

Kit

 

[Cory Cooper]

No worries...let us know what Apple says.

Good luck,

C