Dell U3419W connected via USB C keeps scanning for signal when MacBook is sleeping

Hey Jordy thanks for coming back to me. Absolutely gutted the Dell monitor is still not right - I really had hoped this would sort it. I’ll have a look at some of the LG models. I think I need 85W to charge my MacBook. It’s a 2019 MBPro.

Does anyone out there have any experience with either LG or Samsung USB-C monitors and. 2019 MBPro?

For me it made the issue worst, so I deactivated the power option. At least, I can turn off the monitor so it stop waking up all the time. I will not use the monitor anymore as a USB hub and charger... Really bad, it will be my last Dell monitor.

I can tentatively confirm that @dvdswrd's solution works.

Disabling Power Nap seemed to decrease the frequency of the power connected sound, but it didn't entirely fix the issue.

Enabling "Prevent computer from sleeping automatically..." was the key, as he noted in his post. It's been about a week since I followed those instructions and I haven't heard my MacBook Pro make the power connected sound when it wasn't supposed to. I tested this with the Dell display turned off and with the Dell display turned on but asleep, and it seems to be fixed. 🙌🏻

At the bottom of this U3419DW dell support thread , someone wrote that the U3818DW has a known USB-C PD defect that causes similar behavior when running the same firmware and may be the same issue:

The U3818DW running firmware M3B106 has a defect in the USB-C PD protocol that violates spec and causes similar sleep wake issues. This may be the same issue given M3B106 is the also the latest firmware for the U3419W and the symptoms are similar. See https://www.dell.com/community/Monitors/U3818DW-USB-Type-C-power-delivery-problem/td-p/7452974

If Dell is violating USB-C PD protocol this has nothing to do with Mac vs. PC and really a bug Dell needs to fix.

The linked thread has a USB-C PD dump that shows exactly what the U3818DW is doing wrong:

The Dell U3818DW trace shows how the monitor violates USB Type-C PD protocol and causes a infinite sleep/wake loop:

# Laptop waits ~1 minute, then sends a 3A max current request

0,v2.0,635,2:00.591.836,625.000 us,10 B,,2,Sink:DFP,[2]Request,62 14 2C B1 04 13 CB 3E 34 AF

# Monitor acks the request from laptop

0,,639,2:00.592.359,495.000 us,6 B,,2,Source:UFP,[2]GoodCRC,41 05 34 98 D1 D8

# Monitor Accepts laptop request

0,v2.0,642,2:00.593.160,491.000 us,6 B,,2,Source:UFP,[5]Accept,43 0B B1 D7 5F 0D

# Laptop acks accept from monitor

0,,645,2:00.593.693,496.000 us,6 B,,2,Sink:DFP,[5]GoodCRC,61 0A 07 A1 EA DD

# Monitor violates USB-C protocol by failing to send PS_RDY within 35ms, laptop times out after ~121.3ms and hard resets the link

0,,648,2:00.714.550,276.000 us,0 B,,2,,Hard Reset,

Apparently Apple broke something after 10.14.3. We have been communicating with dell on a similar thread (https://www.dell.com/community/Monitors/U3818DW-USB-Type-C-power-delivery-problem/td-p/7452974/page/2) and their community manager posted that After 10.14.3 Apple broke compatibility with the controller that is used on the U3419W and U3818DW and that Dell cant do anything about it.

"With the release of Apple OS Mojave 10.14.3, Apple introduced a hardware incompatibility issue with our TPS6598E power delivery controller in the U3419W and U3818DW. When connected to the U3419W and U3818DW via the USB Type-C to C cable, if you update the Apple OS to Mojave 10.14.3 or later, you will see the following issues =

* Fully charged Apple MacBook constant "charm" sound due to waking and sleeping

* The monitor will display, "Scanning for Signal"

There will not be a monitor hardware power delivery controller upgrade to correct this hardware incompatibility issue created by Apple. You will need to back down the Apple OS to High Sierra 10.13.6 or earlier.

I received a Dell internal email which stated = There is not workaround to solve the incompatibility with the TPS6598E power delivery controller and the Apple OS 10.14.3. We do not see the issue on Apple OS 10.13.6 and Apple OS 10.12.6."

Dell is wrong to blame this on Apple. It may be true that things worked before 10.14.3, but Apple's USB-C PD behavior after 10.14.3 is still legal and Dell's USB-C PD behavior is clearly illegal. The fault lies on Dell's side.

The USB-C PD protocol traces in the U3818DW USB Type C power delivery problem thread clearly show that the Dell U3818DW monitor is violating USB-C PD spec and the Apple Macbook Pro's USB-C PD behavior is legal. Page 29 of the Dell UltraSharp U3818DW Monitor User’s Guide says "The USB Type-C power delivery compliant port (PD Version 2.0) delivers up to 100 W of power." so Dell either needs to fix this or stop advertising their monitor as USB-C PD compliant because it clearly isn't.

The same issue affects the Dell U3419DW, see the U3419W USB Type C power delivery problem thread. Page 32 of the Dell UltraSharp U3419W Monitor User's Guide says "The USB Type-C power delivery compliant port (PD Version 2.0) delivers up to 90 W of power."

I wonder if this something Apple could take up with the USB-IF compliance group?

Did you find any solutions for those issues?

did you try this solution form the Dell support conversations you linked?

<<I set the Monitor Sleep option in the display's OSD to "Never".>>

I tried this suggestion, and I am still getting the constant scanning for signal. It's pretty disappointing that neither apple or dell will take any responsibility for this issue.

It's clearly a display issue, Dell should fix it, but their response is that it wasn't tested (build) for Mac...

Try connecting the MacBook Pro power adapter to see if that will stop the display from attempting to charge and making that noise.

Thanks for letting me know, back to the drawing board now with my hunt for a monitor!

This patch does not fix the issue from what I can tell. My monitor is on this firmware version and still having this issue of the power connected sound and wake issue with my MBP + Dell U3419W