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View Full Version : Amiga 1200 PAL-B in an NTSC-M world



Kludgy
February 9th, 2010, 12:47 PM
Hi,

I bet this has come up more than a few times in different contexts. ;)

I got my mitts on a European A1200 with KS3.0, so there's no problem soft-switching NTSC/PAL output, and my TV also deals with this just fine. The real problem is the color carrier frequency difference, and as a result the M displays out here in North America come out in black and white.

So of course I've gone searching for solutions that are not insane, like the complex proprietary scan-doublers that exist.

I have read that it is possible to tap what is basically an S-Video signal straight off the mainboard, but I am not willing to do this to the machine. And SCART is not an option in North America.


It looks like the best compromise is an RGB encoder that outputs S-Video or compatible component signals, either/or is fine.

I'm just wondering, what are the cheapest options that yield an acceptable display? Are there any publicly available schematics for building such an encoder at home?


Cheers!

carlsson
February 9th, 2010, 01:56 PM
A wild guess, but what would be results if you connect a NTSC A520 to the back of the 1200? I know the 1200 has a built-in RF but it'll output PAL on both RF and composite video. Indeed you won't get S-Video or component from an A520, but perhaps at least a blurry colour picture?

Kludgy
February 9th, 2010, 02:29 PM
That sounds very promising, very inexpensive!

Thanks for the tip.

AB Positive
February 9th, 2010, 05:00 PM
Also - pal or ntsc will both work on a 1084 or similar amiga monitor the same. You can use a UK amiga on a NA monitor. If you can find one local, it'd probably be cheaper than an encoder.

Kludgy
February 9th, 2010, 05:14 PM
There's not much of that around the northwest pacific anymore, otherwise I'd definitely jump at the opportunity.

geoffm3
February 10th, 2010, 12:19 PM
That's a great idea. As long as the video is set to 60Hz it should work just fine.

The built-in modulator, probably never though.

geoffm3
February 10th, 2010, 12:21 PM
This is probably the best solution. Or, if you can get an Apple IIgs or an early fixed frequency Macintosh monitor (or Atari ST color monitor) that would also work.

Composite video is ugly on higher res computers...especially when viewing 80 columns. I used a composite monitor on my Amiga 500 for a good two years back when I first got that. Ugh.

EDIT: I meant using a Commodore 1080 or 1084 monitor obviously. with the Amiga 1200, you can also get an adapter to connect to a VGA monitor, but you must use > 31kHz horizontal frequencies for it to work, unless you could also find an older multisync monitor that will sync down to 15kHz. NEC's old Multisyncs would do this.

I would opt to use just about any other alternative besides composite if I could help it. ;)

Kludgy
February 10th, 2010, 07:52 PM
Yea composite is pretty ugly. But being in north america there aren't a lot of options anymore.

I am actually looking at a compromise solution either hacking an A520 to get a better signal, or going the route of a newer (more precise) AD724/25 circuit. I've since discovered there are at a few homebrew solutions being produced and they run up to $50.

Cheers!

geoffm3
February 11th, 2010, 03:46 AM
Yea composite is pretty ugly. But being in north america there aren't a lot of options anymore.

I am actually looking at a compromise solution either hacking an A520 to get a better signal, or going the route of a newer (more precise) AD724/25 circuit. I've since discovered there are at a few homebrew solutions being produced and they run up to $50.

Cheers!

CRTs are harder and harder to get for sure.

I would think for homebrew you'd have two options...probably the one you're looking at doubles the horizontal frequency. The other might be to adapt the analog RGB to component video for use on a modern TV/monitor. I think those will do the lower scanrates (since DVD's been around since before HD, it's bound to support 15kHz).

Kludgy
February 11th, 2010, 04:20 PM
There's a great discussion going on regarding similar Amiga encoding issues here:

http://eab.abime.net/showthread.php?t=30752&page=10


Folks seem to be reporting great quality output with a combo of Amigamaniac's AD724 based encoder < 35$ AND an optional additional scan-doubling VGA encoder that can be had for < $40.

I still need to determine whether this will resolve the color carrier problem though. I'm not up on my video signal theory, but would the encoding to S-Video (and hence separation of color) solve this? I'm not sure how true this logic is.