Modified CGA to VGA Scaler to accept clean sync RGB SCART

[BuckoA51]

I'm researching an article on upscaling for a friend and I just wondered if you feed this scaler a 50hz (i.e PAL) signal does it output 50hz VGA or do a framerate conversion?

[Fudoh]

converts to 60Hz. *THE* selling point for arcade operators is that whatever you connect to the input, it will work on a VGA LCD in standard VESA modes.

[justice99]

Hello,

I would like to know if it existe any "all in one" box like the HD BOX PRO, because i have not any soldering skill and sync strike and too expensive for me.

I cant find any good RCA/RGB to VGA box.

Thanks in advance.

[fagin]

Other than making it yourself, the Sync Strike is the cheapest and easiest solution available!

[justice99]

Other than making it yourself, the Sync Strike is the cheapest and easiest solution available!

Yes i understand, but it still expensive, and i will have to buy a CGA to VGA.

I already have the HD Box Pro so i decided to buy a Scart to YUV ( a good clone of the CSY2100, write SCART to RGB on ebay ), what it does is turn rgb direct into component, maintaining the original resolution & hz rate. (240p in = 240p out. 60hz in = 60hz out. Etc.), then i will link it to my HD Box Pro, i have found somebody on assemblers forum saying that it works and looks great on GameCube.

That's the setup : http://i1039.photobucket.com/albums/a47 ... tmap-2.jpg
Probabbly the same price than a modded CGA to VGA + Sync Strike, but with box.

Will see if the quality is nice.

Edit : There is also another cable, write ''cga to vga scart'' on ebay, but it only works with NTSC console.

[fagin]

If you had said you already had the HDBOX Pro then my answer would have been different, and the same as your conclusion.

[emphatic]

So, I'm using this scaler in the supergun I'm building, but I have a huge problem. The picture just keeps growing brighter and brighter until I'm watching a near white screen with washed out stuff that is hard to see. I have to power off and on to get a good picture again.

I'm feeding it RGBS straight from the JAMMA harness and I've tried both MVS 1-slot and a CPS2 with the same results. I'm running the scaler on 12V from the PicoPSU's input power (the lead that then also powers my PSU). Is this a simple power issue or should I worry about the scaler? Same thing happens on LCD screen and Plasma TV.

[bencao74]

Hmmm, but the scaler accepts only 5V according spec...

[emphatic]

I read somewhere it will run on both +12 & +5 volts. To be honest, I might have it running on +5V, it was a while ago I hooked it up. I'm gonna run the scaler on a dedicated power adapter and see if this issue goes away for troubleshooting.

[emphatic]

OK, to troubleshoot, I did some testing with a separate PSU starting with:

• 4.5V (flickering image but works)

• 6V

• 7

• 9 and

• 12V

All of these works like expected but the brightness issue still happens, so I did some checking inside the scaler's menu. I changed the image setting that had the brightness and contrast yanked up to 80 for some reason down to 50 and now I get a stable picture that gives me no issues whatsoever. And this is at 12V btw.

So, I re-connected the scaler to my PicoPSU's 12V (the one leading into the PSU from the power brick) and everything's running 100%. Tested with Progear for 20+ minutes, no issues anymore. Time to finish the input part of my supergun! iPhone pictures ahoy!

[fagin]

[d0rg]

Hi All.

I am going to give this mod a try but am fairly new to electronics. My question is, does it matter what the voltage rating is on the resistor and capacitors? I have found the following on ebay. Would these work?

http://www.ebay.co.uk/itm/ws/eBayISAPI. ... OC:AU:3160
http://cgi.ebay.com.au/ws/eBayISAPI.dll ... 979wt_1107

Thanks heaps for any help!
A special thanks to fagin who got me interested

[sanni]

Hi,

I have bought a GBS 8220 V3.0 (2010.12.20) and added the LM1881 to clean the sync signal.
Now it works very nice with my NTSC N64 (rgb modded, standard Gamecube RGB cable) on 240p games but it refuses to display games that run on 480i.

It also doesn't work with my PAL Gamecube, with the same RGB cable.

Does anyone know why it would display 240p but not 480i?

Thank you very much.

[Whitesnake]

Has anyone noticed a waving swooshing interference over the video when using 800x600 and 1024x768?
You have to look up close to see it.

It looks like electrical interference but I've tried two different power supplies one of them with a ferrite core, I've also tested multiple consoles and some with a ferrite core on the rgb scart lead and none of that has made any difference.

The interference doesn't seem to happen at 640x480 or at 1360x768

is this a flaw in the GBS8220 design?

[fagin]

Hi All.

I am going to give this mod a try but am fairly new to electronics. My question is, does it matter what the voltage rating is on the resistor and capacitors? I have found the following on ebay. Would these work?

http://www.ebay.co.uk/itm/ws/eBayISAPI. ... OC:AU:3160
http://cgi.ebay.com.au/ws/eBayISAPI.dll ... 979wt_1107

Thanks heaps for any help!
A special thanks to fagin who got me interested

Try and stick as close as possible, although for the capacitors it's certainly less of an issue about the voltage (going higher that is).

[fagin]

Hi,

I have bought a GBS 8220 V3.0 (2010.12.20) and added the LM1881 to clean the sync signal.
Now it works very nice with my NTSC N64 (rgb modded, standard Gamecube RGB cable) on 240p games but it refuses to display games that run on 480i.

It also doesn't work with my PAL Gamecube, with the same RGB cable.

Does anyone know why it would display 240p but not 480i?

Thank you very much.

Shouldn't make any difference - does it say "no signal"?

[fagin]

Has anyone noticed a waving swooshing interference over the video when using 800x600 and 1024x768?
You have to look up close to see it.

It looks like electrical interference but I've tried two different power supplies one of them with a ferrite core, I've also tested multiple consoles and some with a ferrite core on the rgb scart lead and none of that has made any difference.

The interference doesn't seem to happen at 640x480 or at 1360x768

is this a flaw in the GBS8220 design?

Not noticed in all honesty.

[Whitesnake]

I'll try and take a picture of it.

[Fudoh]

Why do you want to upscale anyway ? I can't imagine that your TV or monitor does a worse job in upscaling compared the the GBS ?

[Whitesnake]

In this image you can see the interference is more curved and sweeping



and in this one it is more diagonal



it changes constantly and is all over the screen and is more noticeable to the human eye than the camera and pretty irritating.

Like I said before it only occurs when using 800x600 and 1024x768. I've pretty much ruled out power supply and video source as the root of the problem.

[sanni]

Okay this scaler really is a little wierd.
I already tried to fix my problem with the AUTO button countless times. But just now after I did go rampage and AUTO configured the picture 10 times in a row it finally shows a moving picture in 480i.

Can anyone tell me the exact timing of the AUTO button?
I normally press the button for about 5 seconds then let go, the picture then goes black and comes again in 800x600 resolution.
But all the previous times after going black it would just show a missaligned still image in 480i (240p always worked great) and just now it was the first time it actually worked for 480i.

And just in case anyone has a similar problem, the scaler auto configured his settings to (Coast st 07, Coast sp 16, Clamp st 90, Clamp sp 95)

[fagin]

Whitesnake,
You're doing passthru surely in those examples!?

Sanni,
It can be temperamental at times. So your experience is hardly surprising.

[Whitesnake]

Whitesnake,
You're doing passthru surely in those examples!?

Sanni,
It can be temperamental at times. So your experience is hardly surprising.

Yes I just plugged in a laptop for those screenshots, it has the same interference if I use a SyncStrike with an RGB Scart console.

I did that to eliminate the SyncStrike as a possible cause for interference.

So far logical deduction dictates the interference is localised to the GBS8220.

[qeocjcns]

i tried this mod but i have a problem.
the screen shakes up and down.
it only does this for dreamcast games that dont support vga.
im trying to play some bangai-o.
can anyone help please?

[MintyTheCat]

Hello all,

I asked Fagin directly if he had the Pinouts for the Gonbess 8220 and he refered me here - thanks!

I built the Circuit on a Breadboard and then hooked up the Header-Cable and it worked first time. However, I noticed that the Video was a bit jerky and tried adjusting some of the settings. I then tried the Auto Function and it completely screwed everything up I am actually trying to get this up and running with a Megadrive Model #1. What Values should I be using for:

Coast st
Coast sp
Clamp st
Clamp sp

I have my Resolution as 640x480.

I have another Gonbes Board somewhere so I might try that one to then copy the Settings. It would help if I knew what Coast and Clamp actually were.

Cheers.

[fagin]

As per PM, get a video up but this sounds like a sync issue.

[MintyTheCat]

As per PM, get a video up but this sounds like a sync issue.

Hahahaha, well I could try to put up a Video but generally it's hard to tell what's wrong with Video using YT

I experimented with some Settings, namely I found that 1360x768 performed better than 640x480 - that's actually a surprise to me.

My Settings are as:

[Display]
1360x796

[Picture]

B=99
C=64
Sa=98
Sh=10
C. st=02
C. sp=02

[Geometry]

Hp=50
Vp=00
H size=50
V size=50
Clamp st=90
Clamp sp=90

I shall try to take a Video and then upload it tomorrow.

It could be the Upscaler but I should also add that my 'Cable' is actually on a Breadboard at the moment and this 'can' cause Issues wrt Signals.

Cheers.

[MintyTheCat]

As per PM, get a video up but this sounds like a sync issue.

Fagin, I have uploaded a Video to YT but the Quality is pretty bad. I can see the wobbling on it but it's much clearer with the Naked Eye.

https://www.youtube.com/watch?v=j5mzdsoqIoU

It may be easier to simply build the Cable then add soem Capacitors to smooth. I do not have a Scope with me so I can't check the Signals at this Time.

Let me know if you can pick up anything from this terrible Video

[fagin]

I've never seen that extent of wobble before. If you're sure it's not deinterlacing artifacts, I'd look at moving away from your breadboard.

[MintyTheCat]

I've never seen that extent of wobble before. If you're sure it's not deinterlacing artifacts, I'd look at moving away from your breadboard.

Yes, I usually breadboard Circuits before I build anything unless it's really high Frequency but I haven'T had to do any of that for Years.

I'll build a Cable now and get bakc to you

Thanks for the Circuit, it's more than useful as it stands now for development purposes.