ST Scandoubler VGA box

[amiman99]

OK, I had some time today and tested the scan doubler for power requirement.

When the unit is powered on w/o any inputs it uses around 250mA, when there is a RGB input and goes from standby to ON then it uses 400mA.

It does look like the 2A (2000mA) requirement is way over "spec-ed". This is why you can run it using power from the joystick port, I guess the limit for joystick port is 500mA.

Anyone can verify my findings?

[+poobah]

OK, I had some time today and tested the scan doubler for power requirement.

When the unit is powered on w/o any inputs it uses around 250mA, when there is a RGB input and goes from standby to ON then it uses 400mA.

It does look like the 2A (2000mA) requirement is way over "spec-ed". This is why you can run it using power from the joystick port, I guess the limit for joystick port is 500mA.

Anyone can verify my findings?

 

400mA is still quite a lot for the joystick ports.

I'll have to see what the draw is on the ST 5V rail normally.

Where did you find the 500mA spec for joystick ports?

[Goochman]

What kind of PSU should I get? I know almost nothing about these.

I'm using 5v 1200mA (1.2A) switching PS with positive center.

 

Would any of these work?

http://www.amazon.com/gp/product/B001KU44HE/ref=as_li_ss_tl?ie=UTF8&tag=atariage&linkCode=as2&camp=1789&creative=390957&creativeASIN=B001KU44HE

 

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&pa=157340&productId=157340&keyCode=WSF&CID=GMC

[amiman99]

OK, I had some time today and tested the scan doubler for power requirement.

When the unit is powered on w/o any inputs it uses around 250mA, when there is a RGB input and goes from standby to ON then it uses 400mA.

It does look like the 2A (2000mA) requirement is way over "spec-ed". This is why you can run it using power from the joystick port, I guess the limit for joystick port is 500mA.

Anyone can verify my findings?

 

400mA is still quite a lot for the joystick ports.

I'll have to see what the draw is on the ST 5V rail normally.

Where did you find the 500mA spec for joystick ports?

Sorry, I put too many zeros, s/b 50mA http://jack.logicalsystems.it/homepage/techinfo/pinouts.asp?Code=conjoy_amiga_mouse_joy

[amiman99]

What kind of PSU should I get? I know almost nothing about these.

I'm using 5v 1200mA (1.2A) switching PS with positive center.

 

Would any of these work?

http://www.amazon.com/gp/product/B001KU44HE/ref=as_li_ss_tl?ie=UTF8&tag=atariage&linkCode=as2&camp=1789&creative=390957&creativeASIN=B001KU44HE

 

http://www.jameco.co...ode=WSF&CID=GMC

They should fit and work (I verified the dimensions)

[+poobah]

So, I've been trying some approaches to cleaning up the sync signals...

On LCD's, results do vary a bit, largely dependent on the scaling hardware in the panel. I've got a couple 4:3 panels that look pretty good.

Dell 24" widescreen, is just OK. Ben-Q widescreen and Vizio 720p tv aren't too shabby

If you are still rocking a CRT, it looks fantastic.

[Lynxpro]

I'm intrigued by this, especially since back in the day I had to drive from Sacramento to Oakland to buy a very rare VGA monitor - for my Falcon - from ATY Computers that actually could support hertz signal of Atari RGB and display it. I no longer had my SC1224 at that time since I had sold it with my 1040STf to my cousin...

[OBO]

Hi,

 

I bought one of these (those from sandoubler.info), and I'm not completely satisfied with it as it is right now. (Atari STE, UK version, so with RF)

It's not related to the hardware of the scan doubler, so if the creator comes here, guy, don't worry

 

The output is somewhat blurry, there a strange effect around moving objects (like a bending of the picture), and I have little white dots blinking on the screen when i'm in 50hz output (OK in 60hz, strangely)... The VGA cable's ok, I tested it with a PC and it works.

 

Well, it is useful anyway, but I'm kinda spoiled as I'm used to RGB output on Atari computers since my childhood...

In any case, it'll be useful when TV manufacturers will stop providing us in France with SCART input on TVs

 

My next step will be to try it on an Atari 7800 with SCART output. Do you think the joystick port of the 7800 can provide enough power for it ?

[+poobah]

My next step will be to try it on an Atari 7800 with SCART output. Do you think the joystick port of the 7800 can provide enough power for it ?

It would be far better if you obtained a stand alone power supply for it.

[+Stephen]

I agree - the joystick ports are very limited in power output. Pretty sure it's on the order of just a few mA.

[OBO]

So, most my issues are solved.

I changed the port on which it is plugged : no more white dots blinking on black background.

I bought an overpriced VGA cable instead of my cheap one : no more blurry display.

 

There's still the "bending" effect of the picture, in low and med res, but not in high. Not much of an issue in fact in most games.

[+poobah]

I'd still get the external power supply.

The box is (trying) to draw too much current through the joystick port. The doubler box wont like that and may exhibit odd behavior, and the computer definitely won't like it.

The joystick power tap was a very poor design choice.

[OBO]

I agree.

 

I only want to be sure of what to use, 'cause I got mixed answers to this.

5V, OK, but the Amp ? on his description he says 2A, whereas 1.2 seems to be enough...

 

Let's make it clear, I don't wanna fry this box...

[OBO]

Ok, while playing with the cats, I had one of these " Bon Dieu ! Mais c'est… Bien sûr ! "moment when I remembered I had a look at the UK PSU for my SCART to HDMI upscaler. (whoever find the reference for this french sentence wins... errr... 1 Tunisian Dinar ?)

So, after the little brats stopped playing and I gave them food, I tested and it works.

It's a 5V 2A positive centered PSU

Edited July 7, 2012 by OBO

[SIO2]

Looks like I am getting in on this one a little late but, there still might be some people out there looking for a way to display their ST on a VGA monitor.

 

I picked up a VGA-2P board on Ebay for around $28 including shipping. From what I understand this is the same as the GBS-8220.

 

After trying several different techniques for mixing the horizontal and vertical sync signals from my 1040STF and not being able to eliminate screen roll, I tried adding a circuit called Video Sync Mixer for Atari ST which is based on the 74LS86. Diagram is here: http://www.labibleatari.fr/pages/accueil3.html and other places.

 

This circuit worked nicely. I now have a nice stable picture. From the little bit of research I did on this circuit it appears that it works for various models of Atari ST and Falcon. The circuit is easy to make so, I would recommend you try this method first.

 

I found a DM74LS86N on a scrap Intellivision board I have and was able to salvage it to use in this project.

Edited December 23, 2013 by SIO2

[+DarkLord]

Pictures please!?

[+poobah]

Looks like I am getting in on this one a little late but, there still might be some people out there looking for a way to display their ST on a VGA monitor.

here: http://www.labibleatari.fr/pages/accueil3.html and other places.

 

This circuit worked nicely. I now have a nice stable picture. From the little bit of research I did on this circuit it appears that it works for various models of Atari ST and Falcon. The circuit is easy to make so, I would recommend you try this method first.

 

The 74LS86 is definitely the way to go.

[SIO2]

Pictures please!?

 

I put a couple of images in a gallery.

 

I need to clean this up and get it into a case. I just wired the 74LS86 up dead bug style for testing.

 

This is the title of the listing for the VGA-2P on ebay: CGA/EGA/YUV to VGA arcade video converter *US Seller*

Edited December 24, 2013 by SIO2

[+DarkLord]

Thanks for the pics. Does it do medium res as good also?

[+poobah]

Thanks for the pics. Does it do medium res as good also?

 

Seems like med res is always the tough one.

[SIO2]

Thanks for the pics. Does it do medium res as good also?

It is not bad. I can comfortably word process in medium resolution. The stripes picked up by the camera are not noticeable to me as I look at the screen.

It has been a long time since I used an Atari monitor so, I can't really compare the two.

I have not tried any games since I can't find my games disks at the moment.

Edited December 25, 2013 by SIO2

[SIO2]

 

Seems like med res is always the tough one.

 

It looks fine to me in medium resolution. This is a better shot of medium resolution. For some reason in the earlier picture, the camera captured some stripes. I don't see any as I look at it though. Not sure if Full Metal Planette is medium resolution but, so far it looks fine for games also.

[+poobah]

It looks fine to me in medium resolution. This is a better shot of medium resolution. For some reason in the earlier picture, the camera captured some stripes. I don't see any as I look at it though. Not sure if Full Metal Planette is medium resolution but, so far it looks fine for games also.

 

 

There's almost always some weird quantization noise, since the ST image is effectively digitized twice, once at the input to the scan doubler, and again at the input to the LCD. Unless the planets are in alignment, and everything is magically synced, med res will show the artifacts.

You can see it in the first pic in the title bar of the window where there's a regularly occuring vertical space.

It's not a big deal, and the display is certainly quite usable, but it is something I wish that we could avoid. I've put a lot of thought into the issue, and I think there's a big thread somewhere where ijor and I discussed the merits of various approaches. Long story short, the only way to get a nice 1:1 display for all ST modes and refresh rates is with a full frame buffer that's synced to the ST pixel clock, and an ouput LCD that has a native mode that's an integer multiple of the ST's pixel count

[SIO2]

 

There's almost always some weird quantization noise, since the ST image is effectively digitized twice, once at the input to the scan doubler, and again at the input to the LCD. Unless the planets are in alignment, and everything is magically synced, med res will show the artifacts.

You can see it in the first pic in the title bar of the window where there's a regularly occuring vertical space.

It's not a big deal, and the display is certainly quite usable, but it is something I wish that we could avoid. I've put a lot of thought into the issue, and I think there's a big thread somewhere where ijor and I discussed the merits of various approaches. Long story short, the only way to get a nice 1:1 display for all ST modes and refresh rates is with a full frame buffer that's synced to the ST pixel clock, and an ouput LCD that has a native mode that's an integer multiple of the ST's pixel count

Yes, I see it now. Thanks for explaining.

 

For my use and for the low cost of this device, I am happy with it. At least until we can print new SC1224 monitors on our 3D printers

[npturton]

Can anyone post the ST pinouts on here plz, I do not have a Amibay account