Hi @TonyZ, thanks for the update. I’ll make sure to get your unit back and carry out some root cause analysis - if I find out what the problem is I’ll be sure to let you know!
Thanks for being supportive! 
Hello. I’m having the same exact issue with my display as well. The display seems to work fine with non pi-top devices using the display adapter, a powered HDMI cable, and the pi-top power brick. Using a HDMI cable that does not supply power doesn’t seem to work. The display doesn’t leave standby. Not a big deal, but maybe that offers a clue as to what is happening.
Any combination of the pi-top and the pi-top display doesn’t work correctly for me at all.
Using Pi-top to display directly with the green cable (type C to type C) produces the annoying jittering as seen in the first video above.
Using a Pi-top, the display adapter, and the display connected using the green cable and HDMI adapter produces a stable image (no jittering) but with heavy artifacting. It looks exactly like a video card going bad in a PC.
Using the Pi-top, display adapter, my own HDMI cable, and the display doesn’t display an image at all. The display either doesn’t leave standby (like when I use a non-powered HDMI cable and a non pi-top device) or it flashes failing to get sync like seen in the second video above.
All the individual components work correctly. The Pi-top is fine when connected to my own monitor using both the green cable or a normal HDMI cable. The display is fine when connected to a PC/RPI4 using a powered HDMI cable and the display adapter. It’s the combination of the pi-top and the display that causes problems for me.
@cavedude that is very strange indeed! I’m very surprised that pi-top [4] connected directly to the Display doesn’t work as that’s the option with the least amount of interconnects…
Using the Pi-top, display adapter, my own HDMI cable, and the display doesn’t display an image at all.
For this one, have you got a power adapter plugged into the USB-C port on the Display Adapter? The pi-top brick is fine to use. Also, can you try going to the OLED settings and resetting the HDMI as described here.
The thing is, if the Display Adapter works then the Display Cable plugged directly into the screen should be (almost) guaranteed to work. I’m wondering if it’s a power issue on the pi-top [4] or Display Cable - can you try plugging in the Display Cable into the pi-top [4] with the other end into any USB-C device (e.g. a phone) and see if it charges it?
Thank you for your quick reply!
I think you may be onto the issue. When I plug the green cable into the Pi-top and the other end to a phone (I tried two in fact) at best I might get a charging flicker, but most of the time neither charge. I tried both with the Pi-top plugged in and with it running off of battery with no change. In this case, can the display cable be replaced with a standard USB Type C to Type C cable just to test? If that cable works, then we know the display cable is bad. If it doesn’t, then it’s likely the Pi-top. I am not sure if a standard USB cable can be used in this case, so I wanted to ask before I tried it out.
To answer your question, I always plug the display adapter into the pi-top’s power supply when I use it. The Pi-Top Display doesn’t power on at all (no light on power or brightness buttons) without it. I presume this is correct behavior.
@cavedude ok great, seems we are getting somewhere!
You can run another test with just the pi-top Display Cable - plug it into any USB-C power port on any other device you have and try charging another device with it. If it works we know it’s an issue with the pi-top [4] and you can email support to get a replacement.
In answer to your question, yes you can plug a normal USB-C cable into the green display port on the pi-top [4] and power should work (power is the only thing that will work, video and VNC won’t with other cables). This is probably still a good test to do just for the satisfaction of the root cause analysis process 
The only caveat is that there is a small male polarity protrusion on the pi-top [4] so you may have to cut the plastic head a little bit on your standard USB-C cable.
Let me know how you get on!
Got a replacement of the screen, it has the same issue as the old one. I believe that is the power issue.
Yeah, I’m seeing the same thing here. The HDMI cable has to provide power or the display doesn’t leave standby. I can use any HDMI cable I want to connect the Pi-top to another display, so the flaw is either in the display or the display adapter.
So I believe I’ve nailed the problem down to the cable. I’ve since added 2 more tablets to my testing, and all of them have problems charging using the green cable whether it’s attached to the Pi-Top or a wall adapter. At one point I had one phone charging off the Pi-top and green cable for about 5 minutes, and then it just stopped without any interference from me. Using my own USB cable charges every device without problem, whether connected to the Pi-Top or wall adapter.
Now this is where things get strange. I used the Pi-Top and the green cable to power another RPi4 and its 2.5" hard drive. It worked perfectly, and stayed up for about 2 hours before I shut it down. I just tried it again, and again it powered the Pi up and booted it. (As a side note, I am super impressed with the Pi-Top’s battery!) So I am not sure why that test will work, but mobile devices are finicky. But, since the problems persist with trhe Pi-Top not in the picture, that tells me the cable has some sort of issue. Can I have another cable sent to me to try out?
Hi @cavedude, thanks for carrying out those tests! This is good news as a cable swap is a much easier solution. Get in touch with support@pi-top.com, I’m sure they can get a replacement sent pretty quickly!
I’m quite surprised that the Raspberry Pi was able to be powered by the Display Cable, the USB-C power spec is pretty simple for 5V devices as it’s just a straight pass-through of power. There are some resistors in the source/sink side that set the available/desired current but that would be independent of the cable, but I guess if the sink device was more particular about this and it so happened that the CC wire in your Display Cable was faulty it could cause charging errors - maybe this could help explain this peculiar behaviour…
I had this but got it working by, on the pi-top go to settings and navigate down to the monitor icon with the circle arrow and press the circle button and my screen come on
If this issue isn’t resolved, which I suspect it may be, based on lack of activity, would you mind testing out a display adapter bridge? Currently getting ready for prototyping with @duwudi 
To clarify, I presume you mean navigating the system miniscreen menu to the HDMI reset icon?
My issue hasn’t been resolved. Heavy flickering when the Pi-Top is connected to the display using the green cable. Email support never sent a replacement cable out, and they have since stopped responding to me, so I built my own cable (which email support told me wasn’t possible) I get heavy flicking with that one as well.
I’m now having trouble getting the display to work at all using the display adapter. I’ve grown frustrated with this display, and am ready to give up on it.
I’d be happy to test any new hardware you are working on, especially if if helps resolve my issues.
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Ok, PM me your address if you’re comfortable with that. The boards for what I’m planning on should be here in less than a week and I’m hoping to be able to ship some of these out soon. Before I do, I will need to test it on my own hardware to verify it even works in the first place. But fingers crossed.
Out of curiosity, what have you done to try and build your own cable? Because of the high transmission speeds, crosstalk and cable length matter a huge deal. Can you send some pictures? Also, does it work when you use the adapter hardware?
I think my next question would be, if you were to disassemble everything and try the adapter with just your pi, do you get the same results? If you do, youd narrow it down to your pi-top unit or it would be narrowed down to hardware on the pi itself.
If you also have a spare sd card, try the original raspbian image and see what you get.
I know it’s a lot of steps, but it would help to know what configurations are worki g and which arent.
I’m sorry that it hasnt been working though.
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@cavedude I’ll give support a nudge to get this new cable arranged for you!
I’m very interested to know how you built your own cable, can you share details?
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Thanks for any help you can give! The last update I got was they were sending the request over to somebody who would send the cable out and they would give me an update. I haven’t heard anything back and it’s been a while. I sent an update request about a week ago, and haven’t heard anything.
The cable I built isn’t production ready by any means, it was simply more a tool for troubleshooting my display issues, since I have been waiting for the cable to arrive. There is no shielding, or any type of real design. I believe you posted a pinout in another thread. I used that as a start (I think there may have been a typo or 2 on it, but nothing too serious). I then mapped out the video display adapter, to figure out how the HDMI and USB signals were split off in the Pi-Top cable. It’s a really cool cable you guys designed!
Slightly off-topic sidebar Speaking of that, I am not sure if you’re aware but the build quality of (at least my) video adapter board is super poor. A couple of the wires were barely being held on, part of the green plastic piece that holds the wires in place was melted (although, I will fully admit I have since added to that!) there were cold solder joints all throughout, and the one side of the board is rough copper, bad enough that you can cut yourself if not careful. I have since added another (currently non-working) cable to that board to futher my troubleshooting and tinkering, but before I did that I reflowed all the points on the adapter board and did see an increase in video quality.
I then used these nifty breakout boards https://www.amazon.com/gp/product/B08TH8S1J7/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1 to build the prototype cable. Unlike most other male USB-C connectors I found, this one breaks out all of the pins, so I was able to copy the custom cable. It works enough to reproduce the jittering the original cable has, but is also finicky, so another original cable would be hugely helpful in troubleshooting.
@Supernovali I will PM you my address! Thanks! The jittering only occurs when using the green cable/my cable directly. It occurs regardless of OS. I actually am using Ubuntu Mate on it now and see the same jittering that PiTop OS has. Although, the thought has occured to me that it could be a softeware/driver glitch. I have seen similar jittering on touchscreen laptops that has been fixed with a driver update.
I have never been able to get the Pi-Top to work with the video display adapter at all actually using the Pi-Top’s HDMI port. I either get a black screen, or heavy artifacting, similiar to a video card failure in a PC. Before my tinkering, the display adapter did work perfectly with other (non Pi-Top) devices connected to the Pi-Top display (no jittering in that case.) Also, I can connect the Pi-Top to another display using its HDMI port and that works perfectly.
My display adapter is no longer working at all, but it could be due to my tinkering. I see nothing wrong when I check everything with a multimeter though, so I am a bit stumped. I may undo all my custom work and see where I am at. However, since the Pi-Top never worked with the adapter even before my alterations, perhaps there is some underlying issue that I am not accounting for.
By chance, does your jittering look like this? I got this the other day and unplugging and plugging it back it worked… but with all of the troubleshooting you’ve done, I dont think that will fix it.
My adapter just needs some testing to make sure it works too. I’ll be designing a snap on case for it too to 3d print but I’m not quite to that point yet. I do know though that those breakout boards usually cant handle the full 1080@60 fps. The signal to transmit is 3GHz so it requires some careful design considerations and maths to get it figured out.
If you used another display though and it worked, that makes me suspect that it’s the screen. Have you talked to @duwudi about that as well? I know they’re pretty bush but he might have some additional insight as well.
And yeah, that was posted by @duwudi as well in the other post and I did find that typo and had to verify it with him. In that schematic that was sent, pin A11 is labeled as TMDS_D1- and should be TDMS_D0-
I have to get going but if that caused confusion, try adjusting your breakout accordingly
I’ll be on in about an hour and see if I missed anything
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An update regarding the display adapter. I plugged it into my laptop to see if I can get a better idea of what is happening. USB is working perfectly. I have bluetooth off on my laptop, and the Pi-Top keyboard and mouse work great. I also have some touchscreen capability. I can’t control the mouse with the touchscreen, but it is being registered (touching the screen stops the screensaver, or changes the active window.) It also can scroll webpages on Firefox. However, the screen doesn’t display at all. I have tried using both HDMI and HDMI to DP mini. The laptop DOES see the second screen, and unplugging the green cable from the display, or unplugging the USB-C power on the adapter causes Windows to disconnect the second display. I used another display I had to make sure it wasn’t Windows being Windows and that display came right up, with no configuration changes needed.
I have a second cable I built attached to the display adapter to rule out the green cable as being the issue, and it does the same exact thing. I have confirmed continuity on both cables, and all pins on the adpater board, specifically the HDMI port and everything is fine. Could all my issues be due to the logic that is on the hot plug detect pin?
The jittering I normally get looks exactly like the video posted by @TonyZ in the first post. It looks more like the touchscreen isn’t calibrated. The whole screen bounces up and down uniformly. There normally isn’t any artifacting, however I have seen that sometimes when the plug isn’t in all the way, or sometimes the cable needs to be wiggled.
Yes, that was the typo. I assumed it was a typo, and connected the cable the correct way. Plus, I checked continuity on the original green cable and the adapter and confirmed both were wired the same way.