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Main => Monitor/Video Forum => Topic started by: Terminatedrone on October 01, 2007, 01:39:25 am

Title: Computer Wont Start With Monitor Plugged-In
Post by: Terminatedrone on October 01, 2007, 01:39:25 am

Hey guys,

I'm having a little problem with my MAME cab, the computer wont turn on when the Arcade monitor (U5000) is plugged into the AVGA card. It wont post, or even make the beep to let me know its starting. But when I unplug the VGA cable, it starts up fine. After the computer is turned on without the monitor, I can plug the VGA cable in, and everything works fine.

I tried using a KVM switch, and the same problem, when the switch is set to the monitor, the computer wont start, but set it to an open port, and all is well. the AVGA card worked fine with my other MAME cab, and the computer has had no problems before with any other video card/monitor combo.

For the wiring of the VGA cable, I connected the R, G, B, H, V pins, and grounded all the other pins.

Any advice? I'm pretty stumped.

Title: Re: Computer Wont Start With Monitor Plugged-In
Post by: Kevin Mullins on October 01, 2007, 01:50:59 am

Quote from: Terminatedrone on October 01, 2007, 01:39:25 am

and grounded all the other pins.

I think you pointed out your problem there.
That just doesn't sound right to me.

Title: Re: Computer Wont Start With Monitor Plugged-In
Post by: MonMotha on October 01, 2007, 02:54:31 am

Pin 9 on the HD15 "VGA" connector is defined by VESA to be +5V.  On many boards, this will likely just be tied to the system 5V rail.  Grounding this out will cause the power supply to shut down due to the short.

Also, pins 12 and 15 are the DDC subchannel.  Grounding these out may confuse things due to the nature of I2C, though it isn't likely to cause a non-functional system.

Additionally also, pin 5 is reserved and should be left unconnected.  Pin 11 is the "ID" bit and is unused on modern systems and should also be left unconnected.

The remaining lines other than R, G, B, H, and V are ground and are, in most cases, all identical, though some are specified as being the shield ground for the video and sync signals when coax cable is used.  Pin 4 is the "generic ground", 6-7 are RGB ground (in that order), and 10 is sync ground.  There is generally no harm in connecting all these together.

Title: Re: Computer Wont Start With Monitor Plugged-In
Post by: Terminatedrone on October 01, 2007, 11:20:44 am

Sounds about right. I'm not sure why I figured I could just ground all the pins I wasn't using.
Thanks guys, I'll let you know if this doesn't work.