Soft 15KHZ Screen rolls

[joshwaan]

Hi Guys

I have a Sharp Dual Chassis hooked up to my TV Tube a NEC.

I had the guy who sold me the chassis hook up a VGA breakout lead.

Hook up to comuter use soft 15KHZ and screen rolls vertical. It happens when I'm changing res. It's like there no sync at all.

There is a vhold control, but it's bloody annoying adjusting it every few mintues. If I hook this moniotr up to a Jamma board would the sync be better?

I use MAMEFX Direct Draw No streach XFX 7600GT video card.

Thanks

JOsh

[Ummon]

Some monitors are finicky.

[joshwaan]

What annoys me is that everytime I change res no matter what I have to adjust.

Even if I adjust say 401x256 res for 15KHZ and go back to another res I've corrected.

Would a arcade VGA provide the proper sync. Or should I get another Arcade monitor?

I read through the FAQ would I be better off using AVRES, does this all for custom resolutions.

[MonMotha]

It sounds like you're only feeding the monitor horizontal sync, and you're adjusting the vhold until the free-run speed just happens to line up with what the PC is feeding it.  Be sure you're actually sending composite sync to the monitor.  The PC convention is to output composite sync on the horizontal output, so you may just need to adjust a setting.

You also may be using something like positive composite sync, which the monitor may not like.  Arcade monitors almost universally want negative composite sync.  Try to get that set up.

If you can't get your video card to output composite sync, it's not hard to make it.  Composite negative sync is just the XOR of negative horizontal sync and positive vertical sync.  You can do this with a 74LS86 or similar pretty easily.  There are even simple circuits that will auto-detect the polarity of your relevant sync signals.

[northerngames]

Thats what I was thinking it either needs a seperate sync only or composite only but worth a try if you have not done so yet.

I also suggest AVRES Tool if your not using it already.

[joshwaan]

It sounds like you're only feeding the monitor horizontal sync, and you're adjusting the vhold until the free-run speed just happens to line up with what the PC is feeding it.  Be sure you're actually sending composite sync to the monitor.  The PC convention is to output composite sync on the horizontal output, so you may just need to adjust a setting.

You also may be using something like positive composite sync, which the monitor may not like.  Arcade monitors almost universally want negative composite sync.  Try to get that set up.

If you can't get your video card to output composite sync, it's not hard to make it.  Composite negative sync is just the XOR of negative horizontal sync and positive vertical sync.  You can do this with a 74LS86 or similar pretty easily.  There are even simple circuits that will auto-detect the polarity of your relevant sync signals.

Hey thanks for that

So where do I adjust it with powerstrip?

With res of 401x256 and composite sync is greyed out in power strip does this mean it's not enabled?



Thanks

JOsh

[northerngames]

it is how you have your monitor wired and a hardware thing that was suggested prior not software.

where your video input wires go into your monitors chassis what wires are connected to its input.

you should have a seperate H and V on the chassis and need to check if your H and V are seperated or if the H and V are tied together on H to make a composite sync signal.

[joshwaan]

Oh ok thanks for that, I had someone else wire upa VGA lead to the chassis.

Cheers

JOsh