[GH-ISSUE #401] MacBook Pro screen keeps flashing black with Dell P2719H with Type C to HDMI cable #320

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opened 2026-05-05 05:44:36 -06:00 by gitea-mirror · 2 comments

gitea-mirror commented

2026-05-05 05:44:36 -06:00

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Originally created by @himgodfreyho on GitHub (Mar 4, 2021).
Original GitHub issue: https://github.com/MonitorControl/MonitorControl/issues/401

Originally assigned to: @waydabber on GitHub.

Checklist

I have searched for existing issues
I have looked through the Monitor Troubleshooting wiki
I have updated MonitorControl to the latest version

Describe the issue
My MacBook screen keeps turning black and on and black and on again and again when I plugged an aftermarket TypeC to HDMI cable to a Dell P2719H. The Dell screen won't receive any signal and will go to 'standby' mode.

If I close MonitorControl, the monitor will work with the same TypeC to HDMI cable. Once I open MonitorControl (with the external monintor working), the problem happens again.

With the same monitor, if I use a normal HDMI<->HDMI cable and plug into a Typc C dock to my MacBook Pro, the monitor works and the MonitorControl app works flawlessly (e.g., brightness control works).

macOS version: 10.15.7
MonitorControl version: 2.1.0
Monitor(s): Dell P2719H
Mac model: MacBook Pro 15 inch 2019 2.3GHz 8-Core i9 with Radeon Pro 560X
Monitor Cable(s)/Connection(s): (e.g. DisplayPort) Aftermarket (Non-Apple) TypeC to HDMI cable

Originally created by @himgodfreyho on GitHub (Mar 4, 2021). Original GitHub issue: https://github.com/MonitorControl/MonitorControl/issues/401 Originally assigned to: @waydabber on GitHub. **Checklist**  - [x] I have searched for existing issues - [x] I have looked through [the Monitor Troubleshooting wiki](https://github.com/MonitorControl/MonitorControl/wiki/Monitor-Troubleshooting) - [x] I have updated MonitorControl to the latest version **Describe the issue** My MacBook screen keeps turning black and on and black and on again and again when I plugged an aftermarket TypeC to HDMI cable to a Dell P2719H. The Dell screen won't receive any signal and will go to 'standby' mode. If I close MonitorControl, the monitor will work with the same TypeC to HDMI cable. Once I open MonitorControl (with the external monintor working), the problem happens again. With the same monitor, if I use a normal HDMI<->HDMI cable and plug into a Typc C dock to my MacBook Pro, the monitor works and the MonitorControl app works flawlessly (e.g., brightness control works). - macOS version: 10.15.7 - MonitorControl version: 2.1.0 - Monitor(s): Dell P2719H - Mac model: MacBook Pro 15 inch 2019 2.3GHz 8-Core i9 with Radeon Pro 560X - Monitor Cable(s)/Connection(s): (e.g. DisplayPort) Aftermarket (Non-Apple) TypeC to HDMI cable

gitea-mirror

2026-05-05 05:44:36 -06:00

closed this issue
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gitea-mirror commented

2026-05-05 05:44:41 -06:00

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@BuzzwordChief commented on GitHub (Mar 11, 2021):

I have a similar issue with my Caldigit SOHO-Dock. Turning black and on and black and on again. Brightness control does not work. With my no name usb c adapter everything works flawlessly.

@BuzzwordChief commented on GitHub (Mar 11, 2021): I have a similar issue with my Caldigit SOHO-Dock. Turning black and on and black and on again. Brightness control does not work. With my no name usb c adapter everything works flawlessly.

gitea-mirror commented

2026-05-05 05:44:43 -06:00

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Owner

@waydabber commented on GitHub (Aug 21, 2021):

Some docks and active cables mess up DDC communication unfortunatelly. There is no much to do with this, you need to try to use a different cable. :(

I'll close this issue for now, but feel free to comment if there is anything else we can help with! Thanks!

@waydabber commented on GitHub (Aug 21, 2021): Some docks and active cables mess up DDC communication unfortunatelly. There is no much to do with this, you need to try to use a different cable. :( I'll close this issue for now, but feel free to comment if there is anything else we can help with! Thanks!