75inch Displays flickering via HP Docks

[Snaxident]

Wondering if anyone has come across this or a similar issue.

 

Setup is a 75" inch large format display/monitor connected to HP docks we have for testing (the G4 120w Thunderbolt and the G5 USB-C dock) Laptops are the Elitebook 640 G11s and 1 x HP 1080 standard monitor.

Long story short I can only get it working stable on 4k30hz, 4k60 just has constant black screens and flickering or no input at all. Same with both docks, updated firmware on both docks and we currently have a ticket and emails to the HP product/docks team trying to find a solution.

 

The HDMI cable from screen to dock is an AOC Active Fibre Optic HDMI cable, its 15 metres, other types tried wouldn't work at all or were even worse.

It seems to work fine without many issues at all if we plug in direct to the G11 Laptop, suggesting the dock is a bottleneck for some reason.

 

Also recently added a faceplate to simular the setup of cable behind wall and into a faceplate and another short HDMI from wallplate to dock and that has made the 4k30 previously stable had other issues.

These new HP laptops also seem to come with a new resolution 1920 x x1200 which also causing some touch screen issues but thats another issue. 

 

Other schools we setup had the Microsoft 4k Adaptors and they worked great but cannot get them anymore.

[synaesthesia]

By "New" resolution you mean "Proper" resolution  (1920x1080 is an abomination, and many people rejoice that the correct resolution of 1920x1200 is making a comeback!)

Each faceplate is adding a load of interference to your cable runs - eliminate them where possible.

Try lowering the EDID version of the display to 1.4 and see if that makes a difference.

 

[Snaxident]

Had never seen it before, did not know that!

 

Did have the HDMI running through a brush plate before so that's one less link in the chain. 4k30 seems pretty solid without that.

 

The edges of the touch screen go out of alignment on this strange 1200 resolution though, so have to make the 1080 monitor the main display to fix touch on the large display.

 

Will have to wait and see what HP say about 4k60hz not working via the docks.

[synaesthesia]

Yeah, if I recall 1920x1200 was designed to best view 2 sheets of A4 (or letter) side by side but 1080 won over because films/consoles or something

Might just be worth trying to enforce 1080 by software. Also have you had any luck trying different USB C cables? (if the ones on your docks are changeable, our HP ones are and can be sensitive with cables that aren't the original HP supplied ones)

[Snaxident]

We had similar issues in another school and were able to resolve it by changing the EDID to 1.4 which forced them to 1080 which basically solved all our problems, unfortunately on this Philips 75" screens the same setting does not work and it still tries to push the 4k60 no matter what, the change to 4k30 is the only setting that it retains after changing, any attempt to try and get 1080 on Windows doesn't work, just still says active signal res is the 4k. Had some third party software too but it just did not like the laptop and large screen been duplicated and would not force the 1080 setting.

 

The G4 and G5 dock just have one USB-C or Thunderbolt cable wired into it for the laptop so that is the only option, don't think any of the other USB-C ports on it allow you to use them to connect to the laptop.

[mullet_man]

Hi,

 

We have ViewSonic screens and use HP laptops connected to some now very old HP USB C Universal Docks and we've not had any issues with them.

 

Cue a few months ago we had some new TVs installed in some temporary classrooms and I purchased a couple of HP G5 Docks as the other models are not made any more and tested the rooms and all seemed fine with G5 model, but once the teachers moved and used the screens for half hour or so we got issues with flickering.  At first I thought it was cables, so swapped out the HDMI leads but no still happening, updated firmware as each one seems to fix 'flickering issues'.  Long story short I put one of the old docks in and not had any issues, so I've had to buy a few refurb ones from Amazon for these rooms.  

 

I read a Reddit post that you need an active HDMI lead but it seems you've tried that.

 

Edit: I do remember reading some Reddit posts about similar issues and there was a solution posted but I never tested it due to using those older docks.

 

It was to disable DSC, not sure what it is exactly.  

 

https://www.reddit.com/r/sysadmin/s/hO3kVvyp0a

 

Lenovo have a tool that disables it.

 

If you check the thread it claims to have fixed the issues, if you get chance to test I'd love to hear back as we are getting 4 more temporary classrooms ready for September so if rolling out that fix works it could mean I can get G5 Docks for those new rooms.

 

Thanks.

 

Edit 2: The poster here seems to claim disabling DSC worked for him.

 

https://www.reddit.com/r/sysadmin/s/6Kjb2gCuFW

 

Edited May 23, 2025 by mullet_man
Clarity and Reddit post.

[Snaxident]

Just tested this morning and does not seem to have made a difference for our setup unfortunately, still getting black screens/flickering/sound cut outs on 4k60hz. It's really strange that youtube adverts trigger a black screen/flicker almost everytime (but happens just sitting on desktop too).

 

HP say they have raised it with display and docks team, still waiting on a reply from that.

 

Its the G4 Thunderbolt dock we are testing at the moment, if its the G5 dock you have, did you try the DP Alt mode in BIOS, apparently increases the bandwidth for the USB-C G5 dock by decreasing the USB ports and ethernet port.

[mullet_man]

1 hour ago, Snaxident said:

Just tested this morning and does not seem to have made a difference for our setup unfortunately, still getting black screens/flickering/sound cut outs on 4k60hz. It's really strange that youtube adverts trigger a black screen/flicker almost everytime (but happens just sitting on desktop too).

 

HP say they have raised it with display and docks team, still waiting on a reply from that.

 

Its the G4 Thunderbolt dock we are testing at the moment, if its the G5 dock you have, did you try the DP Alt mode in BIOS, apparently increases the bandwidth for the USB-C G5 dock by decreasing the USB ports and ethernet port.

 

That's a shame, was hoping it worked.  

 

Our docks are really old and am having to buy refurbished ones to keep us the same model throughout the school. 

 

The G5 was a good option for us as it removed the need for the HDMI to display port adapter which was an requirement for our current docks.

 

I haven't tried alt mode no, it's worth a test I guess.  

 

How did you raise a ticket with HP? Am happy to try and let them know it's affecting the G5 models too.

[Snaxident]

I logged it on the Business Support tab on support site - https://mycrm.support.hp.com/en-US/

 

It worked using the same logon I made for seeing warranties. 

 

Had already been passed to some of their tech people and Dock product managers by our Account manager, hopefully it will get to the right team. Wouldnt hurt to raise it as well yourself to see what they say. 

 

[mullet_man]

Hi, 

 

I never got round to raising a call, did you get anywhere?  We are due to get our new portacabins soon which will have 4 new rooms and I need to try and commit to what docks to use.

[psydii]

There’s too many variables these days. Laptop chipset, firmware, and drivers, the actually robustness of the usbc port in any given model, the usb c cable quality (even if you get one that meets the required standards, it might not be robust enough for 4-10 hot-dealing events each day), the dock model, the dock’s own firmware(s) (each group of ports seem to have their own firmware updates, though some dock manufacturers obscure that fact), the hdmi cable quality, the board port quality, the board’s own firmware, both at the Android level and that actually running at the hdmi/power level.

 

Sometimes you get lucky and you’ve deployed a working solution, sometime you find next year’s laptops won’t work right, sometimes the cables work for a while, but then become unreliable, sometimes it’s the docks. Sometimes it all works fine and then a firmware update hoses you. 

Generally it does seem to be getting better, if you have a reliable cable supplier, and your board and laptops are in warranty, we’ve found glitches resolved with new  firmware and the vendors already have it when we call.  Having docks in the mix adds a whole additional level of complexity and it’s been not unheard of  for dock vendors to simply EOL the dock rather than fix it, though again this has improved somewhat in the last few years.

 

We recently found some docks started working with a whole class of laptops that we previously never reliable with docks after we replaced some of our 2023

cables (which at the time we were over the moon with as they worked perfectly 100% of the time with 60% of the fleet) with our 2025 cables.

Why did we replace them? Well because they had become damaged.

How did we discover they fixed the problem with the 40%…? Well, a young teacher ignored our instructions and tried the usb-c only lifestyle, found it worked and told their colleagues and eventually we caught a teacher doing it the wild. We are watching with trepidation, maybe this time, maybe this time…

 

[Snaxident]

On 06/09/2025 at 09:17, mullet_man said:

Hi, 

 

I never got round to raising a call, did you get anywhere?  We are due to get our new portacabins soon which will have 4 new rooms and I need to try and commit to what docks to use.

The ticket with HP just ended up going round in circles and them saying they are still testing the issue so did not get very far with that.

 

The G4 Thunderbolt 120W dock seemed to be better than the USB-C G5 dock so we went with the G4, now that the teachers have been back a few weeks it has been going well, the setup that finally worked was as above but setting the large screen to HDMI version 1.4 and the laptops to 4k30hz (60hz still flickered/blacked out constantly), so far it looks and performing quite well. We ran into the "too many USB hubs" issue for the touch screen, cant have more than 5 links between laptop and screen so that is going to mean new USB booster cables. Only screen issues have been youtube adverts still cause a flicker and sound to cut out for some strange reason, no idea what that could be yet, they seem to be running well apart from that.

 

Hopefully new firmware for the dock etc will improve it over time so its not on the limit as only fall back at the moment if something else happened would be wire through brushplate to remove faceplate as an extra link. The Active AOC Fibre HDMI cables was worth it, most of the runs are 10-15 metres. (all the longer rooms are wireless Screenbeams instead)

[mullet_man]

Thanks Snaxident

 

I think we must have got lucky with our docks - HP USB-C Universal, hardly no issues with the image side really.  Replacing the G5 docks with them fixed the issue with screen flicker. 

 

I've spoke with ViewSonic and they have mentioned moving the HDMI version to 1.4 as we are having issues with some long runs in our Science rooms 15m, that's cable not dock though.

 

I'll check out the G4 Thunderbolt docks, I need to make a decision on the new ones, and possible school wide in a year or so.

 

We replaced a lot of our USB ones with ones that have the boosters in the cables and that has stopped the too many hub issues.

 

Cheers.

[Snaxident]

Check out CPC website, had very good prices if you need lots of the fibre HDMI cables. 

 

Have ordered one 15m USB with booster cable to make sure that fixes the too many hubs issue, I think issue is there is a 10m booster cable behind the walls but also a USB-B to A cable from screen connected to it as well although not sure exactly what it is counting.

[Snaxident]

Ok the new USB cables did not work and still causes too many hubs error, the G4 dock must count as two or more hubs inside it as bypassing it is only way to get rid of the error.

[psydii]

1 hour ago, Snaxident said:

Ok the new USB cables did not work and still causes too many hubs error, the G4 dock must count as two or more hubs inside it as bypassing it is only way to get rid of the error.

I saw this exact symptom with a different vendor's dock two days ago, and replacing the laptop-to-dock usb c cable with a "USB-IF Certified USB4" 1.2m cable, *and* making sure the dock-to-board usb connection was via one of the 20Gb/s "USB A" 3.2 ports on the dock, so that electrically it was less likely to actually be daisy-chained off other hubs inside the dock.

Strange thing was prior to having this problem, the cabling/dock/laptops had not complained about "too many hubs".

[Snaxident]

10 minutes ago, psydii said:

I saw this exact symptom with a different vendor's dock two days ago, and replacing the laptop-to-dock usb c cable with a "USB-IF Certified USB4" 1.2m cable, *and* making sure the dock-to-board usb connection was via one of the 20Gb/s "USB A" 3.2 ports on the dock, so that electrically it was less likely to actually be daisy-chained off other hubs inside the dock.

Strange thing was prior to having this problem, the cabling/dock/laptops had not complained about "too many hubs".

The G4 dock has the thunderbolt cable for laptop coming out of it built in so don't think using another one is an option for these. At least its an easy fix for now, USB bypass dock and into laptop instead.

[mullet_man]

On 08/09/2025 at 09:15, Snaxident said:

The ticket with HP just ended up going round in circles and them saying they are still testing the issue so did not get very far with that.

 

The G4 Thunderbolt 120W dock seemed to be better than the USB-C G5 dock so we went with the G4, now that the teachers have been back a few weeks it has been going well, the setup that finally worked was as above but setting the large screen to HDMI version 1.4 and the laptops to 4k30hz (60hz still flickered/blacked out constantly), so far it looks and performing quite well. We ran into the "too many USB hubs" issue for the touch screen, cant have more than 5 links between laptop and screen so that is going to mean new USB booster cables. Only screen issues have been youtube adverts still cause a flicker and sound to cut out for some strange reason, no idea what that could be yet, they seem to be running well apart from that.

 

Hopefully new firmware for the dock etc will improve it over time so its not on the limit as only fall back at the moment if something else happened would be wire through brushplate to remove faceplate as an extra link. The Active AOC Fibre HDMI cables was worth it, most of the runs are 10-15 metres. (all the longer rooms are wireless Screenbeams instead)

 

Am ordering some G4 docks for our new classrooms @Snaxident

 

EDIT: No going for these ones HP Universal USB-C Multiport Hub - Supports dual 4K Displays Via HDMI 2.0 - HP Store UK - They look like updated versions of the ones we currently use so am hoping they work just as well!

 

I'll keep you posted, hopefully have the modulars in by end of Oct HT.

 

cheers.

Edited October 1, 2025 by mullet_man

[Snaxident]

I am not liking the responsibility of that!

 

Things have settled down now and mostly ok, I have re-opened case with HP to still get at them that the dock is still the cause of 2-3 second audio cut outs when you refresh videos or sound for example and the odd black flicker on the 4k screen, but for the most part setting the screens to HDMI 1.4 and 30hz on windows settings has made them all run well.

 

If your HDMI runs are less than the 15m cables we had to get then should have a lot less issues than I had I guess.