Testing, testing

[Darkman]

Hello everyone,

How long does it usually take to fry a VGA monitor with the wrong signal? I've just completed my Dreamcast VGA cable and it is time to test it. It seems wired OK, but anyway, will my monitor explode immediately if I feed 15kHz signal instead of 31kHz? The monitor in question is a Sony CPD-G200E, with dual inputs.

Darkman

[NFG]

Modern monitors will enter standby mode, or display an 'out of range' warning if you feed them a wrong signal.  

Even on old monitors you'll probably find failures are rare.

That said I used to explode monitors in the computer lab by CTRL-ALT-DEL the computers 6 times in a row.  =D

[Darkman]

Thanks for a quick reply! I'll go test it right now and post results later.

[Darkman]

No luck . The image syncs up, but the colors are all messed up. It looks similar to Tempest 2000... I double checked the wiring and everything is OK.  

[NFG]

It's not a DIGITAL RGB monitor is it?  That'll screw up your colours.

And if it's a Nintendo arcade monitor the RGB will be inverted, so white is black, red is cyan, etc.

If you've got sync but your colours are off, and it's not a problem mentioned above, it's almost certainly your wiring.

[Darkman]

No, it's not a digital monitor. Just a regular PC monitor. The weird thing is, however, when I unsoldered some of the ground wires, I got horizontal stripes running over my screen. The colors on those stripes were correct... Tried another monitor(an LCD), but the results were the same. I'm now building the whole VGA box to see what happens.

EDIT: experimenting with the ground wires for RGB I found out that this "analog signal on digital monitor" effect goes away(but not completely) if I run these wires through a large cap. Is there any reasonable explanation to this? I never needed to do that before  :huh: . I have a 1000uF cap soldered there at the moment, but this weird color pattern still appears on screen fadeout. I guess making stuff that is more complex than a cable is just not for me .

[atom]

I guess not. I thought you said you werent using a digital monitor??? Well whatever.

If it is an analog monitor and you have a washed out picture (wrong colors, like a magazine page left out in the sun) then yeah, a capacitor for each of your color lines is what you need.

[Darklegion]

I'm having a similar issue right now,colours are completely off-the-wall psychadelic...quite pretty to look at really,but far from accurate.Only happens when switching into VGA mode...rgb on the same cable looks fine.Someone mentioned in another thread that he was getting "negative" colours...I am not sure if he meant the same thing but apparently he fixed it by running 120ohm resistors through the sync lines...I tried with 75 ohm (all I had) just made the picture very dark.And I do have the caps on each rgb line,not that having makes much difference on the monitor I am testing.The original vga box that I had disassembled works fine,but has too much interference issues for my liking which is why I rebuilt it.There is an ic in that box that I can't read the name of that is probably correcting the sync,I'll try running it through there although I'd really rather not if possible.

Thanks

[Darkman]

You will indeed need 120Ohm resistors. I've omitted them by mistake :rolleyes: . But I didn't have 120Ohm, so I used 150Ohm ones. Cable still works, but only on new monitors. I guess one really needs the buffering IC to make it completely universal.