Konig vga switch - no signal

[ThomasJSmart]

Hi

I have a konig manual vga switch. its a simple box to which i can attach 4 devices and 1 display device. all devices are working except 1 pc.

I removed all devices from the switch except the pc that isnt working. The pc is a standard windows xp pc with a gforce 7600 GS graphics card. i have the latest nvidia drivers (omega drivers cause blue screens, could never get them working). The geforce has 2 dvi outputs. i am using a dvi->vga converter because both my switch and my monitor are only vga.

pc -dvi->vga- ---- monitor : works fine
pc -dvi->vga- ---- switch -- monitor : does not work

booting with either the monitor or the switch yields the same results. booting with monitor and then adding the switch does not work. Booting with switch and then removing switch makes the monitor work again.

if i have the monitor on port 1 of the grfx card and the switch on port 2 with a second monitor neither works. if i remove the switch the port 1 monitor turns on and works again. if i plug the switch back in it goes off again.

all the above tests work fine on my other pc (geforce 9800).

it seems that either the switch is mangeling the signal somehow ( i thought it just simply attached the selected input to the output...??). Or could it be that the dvi->vga->switch->vga->monitor setup is causing wires to be crossed or something like can happen with crossed utp cables? i dont know enough about vga cables to understand it.

any help much apreciated.


I learned a bit yesterday, today i learned a lot, imagine what i'll learn tomorrow!

 

[BadBigBen]

I believe that the GFX card is probably the cause of the problem...

if the Omega Drivers don't work, all other PCs and the 9800 work...

now just to rule out the switch: have you tried the PC on another port, or tried another PC on the port that the non working PC was attached to?

Ben

"If it works don't fix it! If it doesn't use a sledgehammer..."

How to ask a question, when posting them to a professional forum.

 

[ThomasJSmart]

yes i have tried all ports on the switch. while all ports work fine with the second pc none work on this pc.

its like the switch is giving some kind of feedback or short circuit on this specific graphics card.

in the setup that i have a cable direct to the monitor in port 1 of the pc the monitor is working fine. as soon as i plug the second port into the switch, without anything else in the switch nor a second monitor on the switch, the first monitor looses its signal and goes blank.

i was also theorising that it might be that the powersupply on the pc is to weak for the switch if that is even possible??



I learned a bit yesterday, today i learned a lot, imagine what i'll learn tomorrow!

 

[BadBigBen]

If you hook up a monitor to the second port, does the first display also go blank?

in the nVidia Control Panel, is the second port set up and set as clone?

as to the feedback/short-circuit from/within the switch, I doubt that, as that would be evident on all PCs...

one thing you could try though, is to use a totally different monitor cable, I've seen cables (5m+ and some 1m) that would work on one gfx card and not on another...

Ben

"If it works don't fix it! If it doesn't use a sledgehammer..."

How to ask a question, when posting them to a professional forum.

 

[ThomasJSmart]

ok interesting test and results.

i could not get the second grfx port to work.
windows and nvidia did see a second screen but that was just the forced tv option (it called the found screen hdtv). interestingly when booting i did get a signal on both screens but as soon as i entered the windows desktop it lost it.

i then disabled the forced tv option in nvidia and restarted. this time it worked i had image on both screens. i thought it had something to do with the settings so plugged it back into the switch... fail... first monitor went off as soon as i plugged it in and no image on monitor via switch.

in some vague fit of fuzzy logic i thought why not try the utp idea and cross the cable again.. so instead of plugging the 2nd port directly into the switch i plugged it into the VGA-In port of a video2vga device i have. essentially the vga-in feed is passed to the vga-out feed when the device is turned off (turned on it grabs the composite video feed from my cable so i can watch tv on a pc monitor). the vga-out is connected to the switch which is connected to the 2nd monitor... amazingly this worked.

i fail to see the logic, but it works, thats all i care about at the moment >.<


Solution:

PC -- port 1 -- monitor [works]
-- port 2 -- vgaIn (video2vga device) vgaOut -- switch -- monitor2 [works]

and the fail:
-- port 2 -- switch - monitor2 [fails]


if someone knows the logic involved here i would be interested


I learned a bit yesterday, today i learned a lot, imagine what i'll learn tomorrow!

 

[BadBigBen]

Glad you got it to work, albeit in a circumstantial way...

The logic: perhaps there is non, or the signal needed a buffering device which did not pull down on a certain signal, which the switch did...



Ben

"If it works don't fix it! If it doesn't use a sledgehammer..."

How to ask a question, when posting them to a professional forum.