Dell Precision 5760 - Docking Station WD19TB - 2 External displays

@Precision5760  If you have DP to HDMI adapters that claim support for 4K 60 Hz, it sounds like they're active adapters rather than more typical passive adapters.  I'm also not sure why you bought a pair of those rather than only buying one and connecting the other HDMI display to the dock's HDMI output using a bog standard HDMI cable.  The use of two active adapters seems like unnecessary additional complexity and cost when you only needed one, or possibly even none if a passive adapter would have worked for your setup, but I can't tell that because you didn't say anything about your displays other than that they are 27" displays.  27" displays are available in resolutions of 1080p, 1440p, 4K, and 5K.  That last option requires over 7x as much bandwidth as the first one, so it's quite a spread.

Anyhow, one item that strikes me as a possible culprit is that you are cutting power to the dock with a switch.  This may have changed at some point, but I remember that in the earlier days of USB PD, a power source such as a dock could not establish a connection to a device that was already connected when the power source powered up; you had to have the power source powered first.  So if your switch cuts power to the dock while the system is connected and then you switch it back on, that might account for strange behavior.  At least as an experiment, try switching power on to the dock while the system is NOT connected and THEN connect the system to the dock.

And then of course if you haven't already, make sure you're running the latest system BIOS, system Thunderbolt controller firmware, dock firmware, and GPU drivers.  I suppose it is also possible that an update actually broke something -- it certainly does happen -- but unless you have a way to easily roll back to a known good state, such as having image backups of your system from a time when everything worked reliably, it may be tiresome to keep installing older releases.  And even if you succeeded, that old software might auto-update later anyway.

Hi @jphughan,

Yes you are right. Is does say active. Another bad of mine. In that case that would have simply been me not understanding what active actually meant and the consequence of using that adapter as I am. I've not had them long so maybe able to return for passive ones or just put up with it until I get a better display. These displays are not great. They just get a job done.

Just plugged in the 2nd monitor into the DPs HDMI port. There is not so much of an issue with sharpness of images and characters etc but there is a significant difference in contrast brightness and colour etc. Everything just seems washed out. Yes, I know I can adjust these but at the time I saw the DP outputs gave me a better quality image anyhow so I did not bother.

Lesson for me is I've learnt about the impact of using active converters on this doc (and it may happen with other items too).

Cheers,

Barry

@Precision5760 The name of the product you linked specifically says "active" DisplayPort to HDMI adapter, so even if you didn't realize that "active" was as opposed to passive, that's what you've got.  The 60 Hz rating comes into play specifically with 4K, because while 60 Hz has always been the industry standard for displays, in the rush to get 4K displays to market, some early 4K displays and display outputs at the time only handled 4K 30 Hz, which is why you often now see "4K 60 Hz" to mean "as opposed to 30 Hz", since the bygone era of 4K 30 Hz means that just saying "4K" is ambiguous.

Anyhow, you have simple 1080p displays.  Those require only 25% of the bandwidth of a 4K 60 Hz display, so you could very easily have gotten by with simpler passive adapters.

There should not be an image quality difference between using the DP output compared to HDMI.  Both the DP and HDMI outputs on the dock can support up to 4K 60 Hz, and again your display is using only a fraction of that capability, and both are digital signals and therefore would deliver identical image quality with all else being equal about the signal being carried.  So something else is going on there, but without knowing exactly what differences you're seeing in image quality, I can't theorize.  Did you verify that when using the dock's HDMI output, your display was still using the same resolution and display scaling factor as it does when using the dock's DP output?

Hi @jphughan,

Thanks for your detailed response. A bit more detail from myself. Actually the original detail was slightly wrong about the displays. They are two 24 ins LG 24M38H-B displays (not very capable ones). My bad there. I was not aware of such a thing as an active converter between DP and HDMI, this could explain the situation you describe as if I swap the HDMI connection part quick enough before windows realises the two displays do show up. The reason for choosing these particular converters is because they could do 60hz. I did not want to get lower capable ones to only decide later on that I should have bought better ones. A link to the ones I bought is below. The reason for not wanting to use the HDMI output of the doc on these displays however is that the quality of the image is actually visually better (quite significant) via the DPs even through the converters.

I also checked the bios etc on my systems before even using the doc but I think i have since updated an element of the doc. Maybe that's it. 

https://www.amazon.co.uk/gp/product/B07ZNNRYFL/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Regards,

Barry

@Precision5760  I wonder if for some reason the GPU driver is defaulting to different settings when the display is connected via HDMI.  I wouldn't expect that to make a difference, but the existence of firmware updates is proof of the reality that not everything in tech that SHOULD work always DOES work, at least not the way it's supposed to.  And in fact on that subject, I have seen other problem reports here where people have tried using the HDMI output in conjunction with one of the DP outputs where they're using a DP to HDMI/DVI passive adapter and have found that the setup doesn't work, even though it should.  And in those cases, I have suggested that they try using an active adapter instead, and those who have reported back have all indicated that it solved their issue.  One possible explanation for that is that the system sends all video to the dock as DisplayPort, and the dock would then have to convert to HDMI when using its HDMI output or when using a passive DP to HDMI adapter, but NOT when using an active adapter.  So seeing as you've got active adapters anyway already, it may be worth keeping at least one of them.  Or if HDMI isn't cooperating, then there is certainly something to be said for not spending further time in the interest of potentially being able to recover a few dollars by returning one adapter.

But returning to your original question, I would be curious to know if the reliability of your setup improves if you have the system disconnected from the dock when you flip that mains switch, or if you just try leaving that switch on for a while.  The power draw of modern equipment in standby mode should be very minimal anyway, but even if you wish to conserve every possible watt-hour, it might be worth an experiment over a few days.

Hi @jphughan

Sorry for the delay. Just been playing about with this again today a little. Atm the only "apparent" stable way I can get two displays to show externally to the laptop is if I use only HDMI outputs. One coming from the docking station and the other via the adapter from a thunderbolt 4 port on my actual laptop. I will see about getting some passive DP to HDMI adaptors to see if that works but are there any particular ones you recommend? After reading the following it seems you have to be really careful about adaptors.

https://www.tempest-av.com/single-post/2019/02/07/hdmi-to-displayport-and-displayport-to-hdmi-conversion-explained

On the note about the power switch. The only way I use this setup is whenever I shutdown I always shutdown properly before switching off at the mains. I virtually never use the sleep option. Then when I need the PC again I just flick the switch on at the mains and it all boots up. Atm using the HDMI as I am above this all appears to be working just fine. Untidy but ok for now.

@Precision5760  I don’t have a specific recommendation for passive DP to HDMI cables/adapters. I tend to have good luck with products like that from Plugable, StarTech, and Cable Matters. The article you linked about AV setups is a rather different context from a docking station. I’d still be curious if your reliability changes if you leave that mains switch alone for a while and just power up the system by pressing the Power button located on the dock for that purpose. But of course it’s your equipment.

Are you on Windows 11? because I faced similar issues when upgrading to Windows 11. I downgraded back to Windows 10 to get consistent results with displays connected to the docking station. see this post:

https://www.dell.com/community/Precision-Mobile-Workstations/Precision-7560-and-WD19DCS-not-seeing-external-monitors-Windows/m-p/8139631#M8681

Hi,

I know I am late to the party here but I didn't see anyone else mention so I figured I would put my 2 cents in and share what I have seen with Dell and HP USB-C docks happen over the past few years.

Almost all of the docking issues I have encountered the past few years related to type c docks are power related.  These docks are a lot busier inside than the old serial docks and passthroughs they actually contain standalone hardware like their own nics and audio.  I find  my more mobile users who are docking and undocking frequently are affected the most.   The fix I do or have them do is unplug from their dock (usb c to laptop) and also unplug the power to the dock and hold down the power button on the dock 5-10 seconds while it's unplugged to discharge and residual energy the dock has.  The symptoms aren't always the same, sometimes one screen works, sometimes the nic isn't working and they're on wifi, sometimes everything else is seemingly working but the laptop isn't receiving a charge but the fix is the same.  Another thing you could look into is your power settings for when your lid is closed.  Sometimes Windows update will change that back to sleep instead of do nothing so having it docked and closed can put them to sleep even though you never made that setting change yourself.