I have a ThinkPad T490 and an Ultra Docking Station. My external monitors connected to the dock via DisplayPort are not working properly.
My goal is to properly use two external monitors on my T490.
The symptoms are as follows:
- Both external monitors are detected, but only one can be used/addressed by the system (if at all; read further)
- The external monitor starts to turn off and on frequently by itself
- The external monitor displays some kind of green background noise
- The external monitor is not detecting any input and just turns black (this happens most of the time)
- The entire laptop freezes completely when changing the display resolution
These symptoms happen randomly. It is not possible to describe exactly when the problem occurs.
My system is the following:
- Docking station: ThinkPad Ultra Docking Station
- Model: 40AJ
- Firmware: up to date; updated with v3.3.1 fw updater
- Laptop: ThinkPad T490
- Model: 20N3
- Firmware: up to date; BIOS v1.69, Thunderbolt fw 1.1.11.18-N2ITF13W
- OS: Manjaro Linux (up to date, Kernel 5.8.x)
- Connected to the docking station
- Monitors: 2x Dell U2518D
- Connected to the docking station via DisplayPort
- The same issues occur when I use the HDMI port on the docking station, so it doesn't matter if it's DisplayPort or not
- Connected to the docking station via DisplayPort
The Linux system seems not to be the problem. I face the exact same issues when I boot into Windows 10, so I guess this has to be an hardware or (BIOS) configuration issue.
- If I attach an older T480 (running Linux Mint) to the same docking station and monitors, it works flawlessly.
- If I attach a newer T14 (running Manjaro as well) to the same docking station and monitors, it works flawlessly.
The HDMI port on the laptop itself (no docking station) works perfectly, but only allows me to use one external monitor. The USB hub on the docking station works as well – only the display outputs are not working.
What I've tried to fix this issue:
- Updating the docking station, BIOS and Thunderbold firmware
- Using Windows instead of Linux
- Connecting only one external monitor
- Using the HDMI port on the docking station
I don't know what to do here. Can anyone give me a hint to achieve my goal or to solve the problem?
Best Answer
Ok, I found comments on lenovo site to try the following fix, do a full power down reboot - from with the bios, so all is forgot:
This did work. All ports on the laptop and through dock are now happy and working again.
Had one 4k monitor using the display port flash on/off a few times every hour. But some other bios option about when laptop should check and discover pluged in monitor info solved at.
I found this because my laptop was also ignoring the plugged in power pack and not charging correct at full power. I have two usb-c chargers, same voltage, one is much lower wattage than the default lenovo. Once smaller charger plugged in, i got boot time warning - and from that point on Laptop would not recognize bigger charger was in use. Not until bios power off, apperantly once an issue occured it was remembered - and not forgot until full power down.
Maybe this helps. Experiment.