Console only outputs on DVI (TV), but not VGA (monitor)

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MartinB · Post by **MartinB** » Mon Aug 22, 2011 6:03 pm

Hello,

I recently bought a new TV to replace my ageing CRT. I've connected the DVI output of the nVidia GeForce 8400GS to the TV, whilst the VGA output is connected to the monitor.

Problem is, when I boot the PC, the POST and Linux boot/console screens only show on the TV and not on the monitor. Of course, if the TV is off or set to another channel, I don't see the POST or console at all.

I'm just wondering how I can configure the system to show the POST and Linux boot/console on the VGA output instead of the DVI?

The monitor does not have a DVI input, so it is not possible to connect the monitor to the DVI. I've checked the BIOS Setup screen and could not find any options to change it.

Does anyone have an idea of how I can do this?
Thanks,
Martin

tomtom69 · Post by **tomtom69** » Tue Aug 23, 2011 5:51 pm

Hello Martin,

DVI is normally auto-detected. The DVI connector has a detect pin to let the PC know whether a monitor is connected to the DVI port or not.
So if your BIOS doesn't contain an option to disable auto-detect and your TV reports "DVI connected" even when not powered the only possibility I see is a DVI cable that disconnects the hotplug detect pin with a switch or so (see DVI cable pinout for details).
Maybe the TV is only in standby mode and not physically switched off so that it enables DVI hotplug ... did you try to plug off the AC mains of the TV?

tom

MartinB · Post by **MartinB** » Wed Aug 24, 2011 2:44 pm

Thanks for the advice.

It is not possible to power off the TV every time I boot the PC because the TV is often used for other purposes at the same time (e.g. other family members watching TV or playing Wii).

I was not able to find any of the DVI cables with a switch that you suggested either.

If DVI pin 16 is only used to detect the presence of a display, do you think it would work if I just remove that pin? Or would that just break the cable completely? I want to avoid damaging the cable because it took quite some work to thread behind walls and replacing it would not be convenient.

I can't believe that no-one seems to have had this problem before. I surely can't be the only one with VGA monitor + DVI TV configuration?

I hope I can get some more suggestions on how to solve this.
Thanks,
Martin

tomtom69 · Post by **tomtom69** » Thu Aug 25, 2011 6:25 pm

I understand that it is not possible to power off the TV when using the PC - but would this at least solve the issue?

There are some mechanical DVI switches which just switch a DVI output between 2 different DVI inputs. This would also work, however these mechanical switches get rare in favour of electronic switches (with which I am not sure hotplug pin is disconnected). DVI pin 16 removal should work, but DVI cables are somewhat tight so you will eventually break the cable if you do not have much experience in doing such things. Maybe a short DVI extension cable is available, where possible damage is not a big thing?

tom