New Video Adapter for S-Video On Atari ST/TT Systems

[thgill]

I guess this design uses the H+V syncs for the circuit?

[+Stephen]

So, I've managed to resolve the 'dancing pixels' issue, and can output a reasonably decent S-Video picture.

 

There does remain one issue: 50 Hz stuff.

I've gotten varying results depending on the output device, ranging from fine, to black and white only or a rolling color picture.

There's no easy way I can fix this, as it all depends on what your particular tv thinks about a psuedo-PAL picture, so 50 Hz is a crap shoot.

 

So is there any interest in a run of ST S-video adapters that work great at 60Hz, and YMMV at 50Hz?

I would be interested depending on price.

[+wood_jl]

What is the deal with THIS scan doubler thing. I don't know anything, but I'd sure appreciate it if you good technical folks (what's up, Poobah?) would chime in on it!!!

 

 

 

 

 

 

 

eBay Auction -- Item Number: 280888104208

 

 

Does this thing look worthwhile?

[desiv]

Without any real knowledge (where I am most comfortable :-), I'd guess this is based on the GBS-8220

http://www.jammaboar...0-gbs-8220.html

 

(I'm not saying to buy it from that link. It's just the first google hit, but has the specs)

 

I've actually got one on order from ebay (from China, so will take awhile, but it's much cheaper) for my Amiga.

The general consensus is that's it's a good scan-doubler, so figured I'd give it a shot...

 

Not totally sure it's the same board inside, but that'd be my guess...

 

desiv

Edited June 2, 2012 by desiv

[amiman99]

@desiv

You are correct, it is based on GBS-8220 (GBS-8200)

 

@wood_jl

From what I can establish it uses power from the joystick port which is not recommended. The joy ports max draw is 50mA, but I measured that the GBS power draw is at 400mA.

For the use on the Atari they had to create a COMPOSITE SYNC out of H+V, because 15KHz input requires Comp sync and I don't know which method they used.

I have one for my Amigas and it works very well in PAL and NTSC with some fiddling around.

[Foster]

I'm interested. Glad to hear about progress with this.

[+poobah]

What is the deal with THIS scan doubler thing. I don't know anything, but I'd sure appreciate it if you good technical folks (what's up, Poobah?) would chime in on it!!!

eBay Auction -- Item Number: 280888104208

Does this thing look worthwhile?

 

It's almost certainly a GBS-8220.

The video quality on those varies quite a bit depending on your output device. It looks good on a quality CRT.

LCDs are tougher, some look great, some not so much, depending on the scaler in the LCD controller.

Essentially, we're taking an analog signal, sampling it, manipulating it, converting it back to analog in the GBS-8220, then repeating the process in the LCD.

 

I'm not super excited about this particular design.

As amiman99 noted, it is drawing far too much power from the joystick port.

However, Goochman bought one and last I heard he was happy with it.

 

Because it is a decent all in one solution, I'm working up a version with a proper power supply, a nice case and a built in mono/color switcher.

Alas, it won't be cheap, at least $100, probably more. My prototype is almost complete, I post some pictures when it is done.

[+DarkLord]

Okay, count me in for one then, of your design. Thanks!

[desiv]

From what I can establish it uses power from the joystick port which is not recommended. The joy ports max draw is 50mA, but I measured that the GBS power draw is at 400mA.

I've also heard that it is very picky on it's power. I wants 5V. Not much more or less. I think the information states 2A required.

I ordered a 5V 2A supply, just to be safe, but I figured it was probably much less than 2A.

I know all the Amiga guys were saying NOT to use the 5V on the video port, as it doesn't have enough AMPs. I think they were talking about the Parallel or Serial port.

I just figured I'd use a separate adapter. I have my setup on it's own power strip anyway.

 

I feel kind of bad now.

I had a 520STF but not M (before I realized there was such a thing). I never used it because I never had anything to video it out to...

Finally gave it away... (Yeah, I could have done VGA straight, but I wasn't really looking for mono hires)

Since then, I have acquired a few 1084s monitors and now this thing probably would have worked. Oh well...

 

desiv

Edited June 2, 2012 by desiv

[thgill]

I am not a fan of the GBS board for a couple reasons. Biggest one being that everything gets frame rate converted to 60hz. Play a euro game or demo, and it gets sampled up from 50 to 60hz. Kills smooth scrolling and results in jerky scrolling and movement.

 

Depending on your intended use it can be fine, just keep in mind it only outputs 60hz and everything gets converted to that.

 

And I agree with poobah, it looks better on a CRT.

[Goochman]

It has sworked great for me - no complaints, but being an NTSC user the 50mhz issue isnt a problem. It also looks good on my LCD monitor.

[Goochman]

Ah it seems he now supports all 3 ST resolutions from 1 box:

 

"

Will convert both Low and Medium resolution screen modes in colour, it will also display High resolution screen mode in monochrome

Monochrome mode turns off the scandoubler and passes through the Atari monochrome signal unchanged"

 

He told me it wouldnt work on the one I bought since he had to add a switch I believe for it to provide to correct signal to the Atari.

[+poobah]

Ah it seems he now supports all 3 ST resolutions from 1 box:

 

"

Will convert both Low and Medium resolution screen modes in colour, it will also display High resolution screen mode in monochrome

 

Monochrome mode turns off the scandoubler and passes through the Atari monochrome signal unchanged"

 

 

He told me it wouldnt work on the one I bought since he had to add a switch I believe for it to provide to correct signal to the Atari.

 

 

Yah, you need an analog mux, though it probably could be retrofitted.