I have a presentation setup in a church, consisting of Dell Inspiron 5415 laptop (Windows 11) from which I run an HDMI cable to a (powered) HDMI splitter (Pro Signal PSG3430); from there, one HDMI cable runs to a projector and a second runs to a TV. The laptop, projector and TV all have native HDMI ports (i.e. no adapters). Windows is set to extend the display: main screen is the laptop screen, extended one is the HDMI out.
When I power everything up, the extended desktop appears on the projector perfectly, but the TV shows a blank screen as if there is nothing connected/no valid signal. Plugging the laptop directly into the TV (i.e. without the splitter) it works, but as soon as the splitter is put between then, the TV stays blank - even though the graphics settings in Windows are identical and even if the projector is not connected to the splitter. Tried all combinations of cables, with/out projector connected, power on and boot order, and cannot get anything on the TV screen if the HDMI splitter is involved. The projector is fine in all setups.
But, if I replace the Windows laptop with my MacBook Pro (2023 Apple M3; Sonoma 14.7), the TV immediately works fine (as does the projector) and if I then unplug the MacBook Pro and go back to the Windows laptop, that works as well! But after the system is powered off the problem recurs until I use the MacBook Pro. The Windows graphics settings (resolution, colour depth, refresh rate, driver) appear identical when it is working and when it is not.
This shows that the setup and all components are fine, but for some reason the Windows-splitter-TV config doesn’t work until I’ve plugged the MacBook Pro in first. Obviously, this workaround is not viable long term.
I am completely at a loss: it makes no sense to me and I can’t find any Windows graphics settings that differ between working and non-working configs. Maybe there’s something about the signal timing that the MacBook Pro handles and Windows doesn’t?