I’m running Fedora Linux 43, but I don’t believe this issue is related to that
I have the Framework 16 with Ryzen 7 7840HS and an RX 7700S expansion bay module
Most of the time I leave my laptop docked, and my expansion slots are set up as follows:
Charger
HDMI out to display
USB-A to mouse dongle
USB-C dock with 4x USB-A (for peripherals), Ethernet, and HDMI out to display
Audio out to speakers
USB-A to nothing
I have a DisplayPort USB-C cable running between my GPU and another display.
This afternoon I unplugged everything to take my laptop with me, and at that time, this setup was working perfectly. However, when I returned and plugged everything back in, the monitor connected to the HDMI out card in slot 2 was not displaying anything.
The same issue occurred when switching to a DisplayPort card instead.
When I swapped which monitor was using the card and which was using my dock, the one connected to the dock would always work and the one connected to the HDMI card would not.
When I swapped which expansion slot the HDMI card and the USB-C for the dock were connected to, suddenly the HDMI card would always work and the USB-C dock would be unable to display a video signal. No other functionality of the dock was lost.
I have tried this both with my Fedora 43 setup and with a live boot of XFCE Debian, both of which experienced this issue. Both are able to see the USB device itself as far as I can tell, but none of them show the display in their display configuration menus.
From this testing, I am led to believe that there is something wrong with the video functionality on slot 2. Is there something I can do to fix it, or is it toast? Or am I just wrong?
Just for fun I decided to switch the positions of card 1 and 2, so the video card would be in slot 1 and my power would be in slot 2. After doing this, both of them work, so my workflow is no longer restricted. If a solution to this problem can’t be found, I would at least like to know what I did to cause it, so that I don’t lose video on all of my slots.
I did use that diagram, and its what I based my numbering of the slots on.
It says that slot 2, the one I was trying to use, supports video out. Not to mention that my HDMI card was working in that slot earlier, so I am certain that video is supposed to work in that slot.
I have external PSUs for two of my monitors, and one takes a standard PC power cable. All three of them have three-prong mains plugs, but the monitor that was plugged into the port that stopped working seems to have the barrel jack on the other side of the PSU output across only two separate wires (photo attached)
For a PSU with 2-pin mains plug.
The PSU output has a GND and a VCC Volts+
Of if USB-C, the shield is the GND and the VBUS is the VCC Volts once negotiated.
That is the same for a PSU with a 3-pin mains plug.
The difference is the potential difference between the Mains earth and the GND shield.
If we assume the Mains earth is at 0V.
For a 3-pin PSU, the GND Shield will also be 0V.
For a 2-pin PSU, the GND shield can be 70V or more. (not dangerous as the current is limited)
If you plug a 70V GND into a 0V GND, it can interfere with the USB-C negotiations while the two GNDs even out.
If all the PSU main plugs are 3-pin, all the GND Shield will be at 0V, and thus not cause any problems when you plug them together.
So, while 2-pin mains plugs are safe, if you have a computer with lots of different devices plugged in, some with 2-pin mains, and some with 3-pin mains, you can see how that might cause problems.
Interesting. I think that is not my issue then, because the only device I have with a two-prong mains connected to the laptop is an Ethernet switch, and as far as I understand it isn’t plausible for the switch to cause issues purely through an Ethernet cable connection.
