A520 modulator and VGA outputs

Hi, have done a search of the forums and can find nothing close to this query, so I guess it's probably a really dumb one. But I can't see why the following wouldn't be possible.

Can I use (with cables/minor tweaking) an A520 Modulator to send a viewable signal to my TV (preferably composite, but RF modulation would do) from an output on my laptop (VGA, docking station port, serial, parrallel, etc)

The reason I put more than VGA above was that the modulator seems to be a female serial port.

Picture quality is not a big issue, just getting a VGA signal on my TV without spending money.

Any help or a definitive no would be greatly appreciated.

[Uplink7]

First of all lets try the easy question. A serial port is a 25 pin connector (or 9 pin) and the 520 has a 23 pin connector so they won't mate. I won't go into the fact that a serial port has nothing to do with video, vga or otherwise. Also a 520 is looking for a standard analog RGB type signal that it combines to composite or modulates to RF. VGA is not. There are some cheap VGA to composite adaptors but as with all things cheap usually means poor resolution. Then there is the matter of what screen size you are using 800X600 1024X768 etc.

[alexh]

Originally Posted by uplink7

Also a 520 is looking for a standard analog RGB type signal that it combines to composite or modulates to RF. VGA is not.

Erm yes it is.

Originally Posted by uplink7

There are some cheap VGA to composite adaptors but as with all things cheap usually means poor resolution

"AverKey3" by Avermedia are the cheapest VGA -> Composite (S-Video) converters at about £50 they do upto 1280x1024.

Originally Posted by uplink7

Then there is the matter of what screen size you are using 800X600 1024X768 etc.

To stand any chance of using the A520 you'd have to use 720x576@50Hz interlaced or some other similar resolution (720x480@60Hz interlaced etc.). If you couldn't control your PC gfx card to that level you'd be stuffed (although I think most cards can be using PowerStrip).

If you have RGB SCART on your TV you CAN just make up a 15 pin VGA -> SCART cable and use software like AdvanceMame which controls the VGA output to bring it within PAL / NTSC standards.

[Jope]

Originally Posted by alexh

Erm yes it is.

It's analogue RGB, but the refresh rate is wrong. Hence you can't just wire them together.

[Uplink7]

Try this page, it has a lot of info.

http://www.hut.fi/Misc/Electronics/circuits/vga2tv/

[alexh]

Originally Posted by Jope

It's analogue RGB, but the refresh rate is wrong. Hence you can't just wire them together.

I know.... but if you see what I put I mentioned this. HOWEVER with the right video card and the right drivers, programs like advancemame CAN set interlace and set the right refresh rate so you can just wire them together (perhaps some resistors & diodes to get the right voltages)

http://www.mameworld.net/dosmame/advanced.php

http://www.advancemame.com/index.php

[Jope]

Heh, that's cool.

Some video cards can be made to output low refresh rates under Windows too using powerstrip.

[alexh]

I dont think it's the low vertical refresh rate that is the major issue.. it's the interlaced screen mode and 15KHz Horizontal Frequency. Most TV's will do 50, 60 and even 70Hz. The Atari ST relys on this for some of it's cool tricks.

[Jope]

Maybe I should have been specific about which refresh rate I was talking about, so thanks for the clarification.

Still, powerstrip can be used to make 15kHz modes on some VGA chipsets.