Modified CGA to VGA Scaler to accept clean sync RGB SCART

[fagin]

Since the release of the SLG3000 I needed to look at cheap solutions to enable a retro console to connect to an appropriate scaler. The scaler had to accept SCART RGB and obviously output VGA via a DSUB15, which could then be fed in to a SLG300 and finally to a LCD / Plasma.

RGB SCART from a retor console does not have a separate H & V sync, which is what is needed for most CGA scalers. Finding a scaler with a RGB input is fairly difficult, especially for a good price here in the UK. One of the commercial solutions would be to buy a HDBOX Pro and then a SCART to Component transcoder.... this is not that cheap by the time you have bought the transcoder and is slightly messy. The other solution is to buy a SYNCBLASTER cable. These cost around £70 on their own!

The ideal solution is to have something that accepts an RGB SCART signal and splits / amplifies the sync, so I decided to make my own complete solution (just as an experiment and to help out some mates).

I took a CGA to VGA Scaler from Ebay, which uses the same chipset as the HDBOX Pro and costs a very reasonable £50.

I then bought the parts required to build a sync stripper / amp and the interconnects etc.

This comprised of:

LM1881 IC
680k ohm resistor
2 x .1uf disc capacitor
Female SCART connector
2 x phono connectors (for audio breakout from SCART)
PCB to mount components

Total cost about £7 for parts.

A sync amp / stripper is very easy to build and there are various schematics on the net.

Here is one (curtesy of gamesx.com):


Ignore pin 7 & 5 on the IC as it is not needed.

Pin 1 on the IC is HSYNC.

Both IC grounds can be connected to the composite ground on the SCART plug (pin 17).

Composite Input is SCART pin 20.

The CGA to VGA scaler has a RGBHV header and loom provided.

Wire the RGB of the header loom to RGB SCART (pins 15,11 & 7).

Wire the HSYNC of the header (grey) to pin 1 on the IC.

Wire the VSYNC of the header (yellow) to pin 3 on the IC.

Wire the GROUND of the header (black) to SCART pin 17.

Wire COMPOSITE SYNC from SCART (pin 20) to the capacitor in-line with pin 2 on the IC.

Wire IC Pin 8 (power) to the positive on the CGA to VGA scaler.

Wire the phono audio breakout to SCART pin 2,4 & 6 (Right, Ground and Left).

Job done!!! Tested and working!











Assuming you buy a case, you are talking about £65 all in for a CGA / VGA Scaler that has SCART RGB (with sync stripper / amp), Component (this scaler already has this input), DSUB15 and JAMMA connections.

[Fudoh]

nice work! Will you add a case ?

btw: when's your Cinemateq coming in ?

[emphatic]

Very cool. How is it powered?

Edit: Do you have any photos of it running with the SLG3000?

[Sparda]

Awesome great work ^_^

since the cga to vga scaler is a "kind of" HDBox Pro clone, did you think we can add the same input ?

Can you upload some closeup of the stripboard, both faces ? did you cut some track or not ?

[KBZ]

I have a similar setup, but I just use the plain RGBS header with the sync cleaner that came with my JROK. Why did you need to use the H/V sync header? I thought that was for medium res and 480p.

[fagin]

Fudoh,
I was going to add a case, but that means I will have to fit remote menu buttons etc to the top of the case...... I also need to find a case that either fits the board exactly (so existing surface mounted connectscan be used still) or again remote fit connections. I don't think I can be arsed.

Cinemateq *should* be with me by the end of the week!

Emphatic,
The sync circuit is powered off the scaler, which is powered via a 5v supply. One power feed needed only for both devices.

Will get some pictures up tonight mate.

Sparda,
This scaler has the same inputs as the HDBOX Pro and MORE!

The stripboard was for IC use, so had the middle channel taken off, but I also ended a few tracks..... you will see on the images I upload tonight.

Kingbuzzo,
I didn't have to use the RGBHV header, but since the scaler comes with a RGBHV header loom it made sense to use that. I have no spare JAMMA video loom so it was a no brainer.

[ckong]

Hahaha, what a coincedence. I have been making the same connection myself last night. I used a completely build sync splitter which I once made for a console>jamma project (it was working but messy with all those wires and therefore obsolete, Villetim's first series adapter is so much more elegant ) and the same CGA to VGA scaler. The only difference with your solution is that I used the 5-pin RGBSGr connector.

But it didn't work. When I switched my Megadrive on (with a RGB scart cable) the monitor screen turned from completely green (the colour of the scaler when powered on) to pink, but no game image. I tried to get ot to work but I couldn't. So, just a few hours ago I gave up. I had already decided to buy the very expensive syncblaster cable, I disassembled the scart cable, put the sync circuit back in a box and threw the messy scart cable with all the loose wires away.

LOL, I guess I will take it out of the bin again and try harder to get it to work, with the help of this topic.

[emphatic]

Emphatic,
The sync circuit is powered off the scaler, which is powered via a 5v supply. One power feed needed only for both devices.

Will get some pictures up tonight mate.

Thank you kind sir!

[fagin]

Hahaha, what a coincedence. I have been making the same connection myself last night. I used a completely build sync splitter which I once made for a console>jamma project (it was working but messy with all those wires and therefore obsolete, Villetim's first series adapter is so much more elegant ) and the same CGA to VGA scaler. The only difference with your solution is that I used the 5-pin RGBSGr connector.

But it didn't work. When I switched my Megadrive on (with a RGB scart cable) the monitor screen turned from completely green (the colour of the scaler when powered on) to pink, but no game image. I tried to get ot to work but I couldn't. So, just a few hours ago I gave up. I had already decided to buy the very expensive syncblaster cable, I disassembled the scart cable, put the sync circuit back in a box and threw the messy scart cable with all the loose wires away.

LOL, I guess I will take it out of the bin again and try harder to get it to work, with the help of this topic.

Mine didn't work the first time I tried it as I had taken the +5v (to power the LM1881) off the wrong point on the scaler PCB!

If you need any help mate.... I will do my best to advise. I hope the pin out details I have given above should give you all you need.

[trunk]

...
Wire the GROUND of the header (black) to SCART pin 17.
...

I just wanted to make sure I got this straight. In the picture it appears that the ground header wire is going to the lm1881 connected to pin 4 and 6(after res and cap) and that pin 17 on the Scart connector is connected to that vs what is quoted above. I know that either way you connect is the same:

anchoring the gnd header wire to SCART pin 17 (as explained)

vs

anchoring the gnd header wire to lm1881 pins 4,6 (as shown)

Either way it should be good to get the same ground point so that they have the same reference?(Like when you run two ac adpter devices on a power strip vs 2 different power sockets)

I ordered some lm1881's and the converter and plan to make this. Thanks for the good information.

[fagin]

...
Wire the GROUND of the header (black) to SCART pin 17.
...

I just wanted to make sure I got this straight. In the picture it appears that the ground header wire is going to the lm1881 connected to pin 4 and 6(after res and cap) and that pin 17 on the Scart connector is connected to that vs what is quoted above. I know that either way you connect is the same:

anchoring the gnd header wire to SCART pin 17 (as explained)

vs

anchoring the gnd header wire to lm1881 pins 4,6 (as shown)

Either way it should be good to get the same ground point so that they have the same reference?(Like when you run two ac adpter devices on a power strip vs 2 different power sockets)

I ordered some lm1881's and the converter and plan to make this. Thanks for the good information.

As long as you connect ALL GROUNDS to PIN 17 on the SCART you will be good to go.... how you bridge them (if you decide to do that) is up to you! If you look at the PCB I made you will see the link wire on top, going from IC pin 6 to 3. I then connect IC pin 3 to PIN 17 on the SCART (along with the ground from the header on the scaler). Happy days.

[Sparda]

i bought the parts few hours ago..4,50euror at my local electronic shop :p now i just need to order the converter

Did the vga input share common points with the rgb input on the board ? If they share common points, maybe we can adapt the "hack" to HDBox Pro. Ill order one unit next week.

[fagin]

i bought the parts few hours ago..4,50euror at my local electronic shop :p now i just need to order the converter

Did the vga input share common points with the rgb input on the board ? If they share common points, maybe we can adapt the "hack" to HDBox Pro. Ill order one unit next week.

I am not sure this will work with the HDBOX Pro as I *think* the DSUB15 IN on that is only used as a passthru, not as a CGA input to go through the scaler. I could be wrong though.

[fagin]

Yep... according to the HDBOX Pro website the DSUB15 IN is purely for VGA passthru!

[KBZ]

that's correct, whereas the vga in on the cga2vga isn't passthru if I'm correct.

[fagin]

Fudoh,
I missed a delivery today from the Post Office.... could this be the Cinemateq waiting for me at the Post Office.

Emphatic,
They say a picture speaks a thousand words.... a video will speak even more!

http://www.youtube.com/watch?v=Gvv4rHRaVpk

Sparda,
Don't mock my "bird shit" soldering..... the tip was mullered on the iron!

[fagin]

that's correct, whereas the vga in on the cga2vga isn't passthru if I'm correct.

That is correct.... the DSUB in is for CGA that will be upscaled.

I can accept the fact that this device does not have the motion detection software on it (like the HDBOX Pro), for the multitude of connections (especially after this mod) and purposes it contains over and above the HDBOX Pro.

[Fudoh]

I can accept the fact that this device does not have the motion detection software on it

really ? Ever tried to play a Mega Drive or PC Engine shoot'em up on it ? Those use 30Hz flicker all the time - clouds, enemies, shadows and it can get real messy without it.

[fagin]

I can accept the fact that this device does not have the motion detection software on it

really ? Ever tried to play a Mega Drive or PC Engine shoot'em up on it ? Those use 30Hz flicker all the time - clouds, enemies, shadows and it can get real messy without it.

I'm not suggesting it would not look better, but it is not a showstopper for me......

[Fudoh]

I already see you selling this one once the Cinemateq hits you. I'm looking forward to your impressions. I haven't seen their linedoubler model, but it should be close to the other ones...

[emphatic]

Thanks for the video, it looks stellar!

[fagin]

I already see you selling this one once the Cinemateq hits you. I'm looking forward to your impressions. I haven't seen their linedoubler model, but it should be close to the other ones...

I doubt I will sell it as I have no real use for it anyhow.... it was all about experimentation and knowledge building. I normally use my arcade CRT's for all my retro gaming with direct connections.

It certainly will be interesting to see how the Cinemateq shapes up. I will let you know.

Emphatic,
No problem mate.

[ckong]

..... Wire IC Pin 8 (power) to the positive on the CGA to VGA scaler.

Your tut is very easy to follow, but I don't see you mention something about connecting the ground wire (black wire) of the 5V power connection on the scaler. Shouldn't that be connected to one of the grounds of the sync circuit?

[fagin]

..... Wire IC Pin 8 (power) to the positive on the CGA to VGA scaler.

Your tut is very easy to follow, but I don't see you mention something about connecting the ground wire (black wire) of the 5V power connection on the scaler. Shouldn't that be connected to one of the grounds of the sync circuit?

Which ground are you referring to?

I have said the black ground on the header needs to go to pin 17 on the scart socket.

[ckong]

Which ground are you referring to?

I have said the black ground on the header needs to go to pin 17 on the scart socket.

I'm referring to the 2-pin 5V header on the scaler, next to the 5V jackplug. Like you I try to power the sync circuit from the power of the scaler. So I wanted to use the 2-pin header for that: the red wire of the 2-pin connector (which came with the scaler) goes to pin 8 of the IC and the black wire of the 2-pin connector goes to pin 6 of the IC. At least, that is what I would think, but I'm not an electricien.
It could be that your option to connect the black wire of the 8-pin connector, together with pin 6 and pin 4 of the IC, to pin 17 of the scart also makes a 'closed' circuit for powering the cync circuit.

But I'm probably doing something wrong because after my second attempt I only get the message 'no signal' on my LCD. I can access the scaler menu, so I know that is working, I guess the message means that there is something wrong with my cync circuit.

[fagin]

Which ground are you referring to?

I have said the black ground on the header needs to go to pin 17 on the scart socket.

I'm referring to the 2-pin 5V header on the scaler, next to the 5V jackplug. Like you I try to power the sync circuit from the power of the scaler. So I wanted to use the 2-pin header for that: the red wire of the 2-pin connector (which came with the scaler) goes to pin 8 of the IC and the black wire of the 2-pin connector goes to pin 6 of the IC. At least, that is what I would think, but I'm not an electricien.
It could be that your option to connect the black wire of the 8-pin connector, together with pin 6 and pin 4 of the IC, to pin 17 of the scart also makes a 'closed' circuit for powering the cync circuit.

But I'm probably doing something wrong because after my second attempt I only get the message 'no signal' on my LCD. I can access the scaler menu, so I know that is working, I guess the message means that there is something wrong with my cync circuit.

Are you using the power header to power the scaler or the jackplug? It sounds like you are using the jackplug to power the scaler?! If that is the case the power header is redundant. You need to take the positive from the jackplug (it's the rear underside solder joint on the scaler PCB) to IC pin 8. The black wire from the RGB header goes to PIN 17 on the SCART cable, along with your two grounds from the sync circuit, IC pins 4 & 6. You don't connect the ground from the power plug (on the scaler) to anything!

[trunk]

As long as you connect ALL GROUNDS to PIN 17 on the SCART you will be good to go.... how you bridge them (if you decide to do that) is up to you! If you look at the PCB I made you will see the link wire on top, going from IC pin 6 to 3. I then connect IC pin 3 to PIN 17 on the SCART (along with the ground from the header on the scaler). Happy days.

Thanks for the clarification, I'm also going to take a guess that you meant pin 4 of the IC in the above statement.

[fagin]

As long as you connect ALL GROUNDS to PIN 17 on the SCART you will be good to go.... how you bridge them (if you decide to do that) is up to you! If you look at the PCB I made you will see the link wire on top, going from IC pin 6 to 3. I then connect IC pin 3 to PIN 17 on the SCART (along with the ground from the header on the scaler). Happy days.

Thanks for the clarification, I'm also going to take a guess that you meant pin 4 of the IC in the above statement.

Sorry... yes IC PIN 4.

[fagin]

I have just taken delivery of a Cinemateq Picture Optimizer, which in it's day was a (price wise they were over £1k when new) higher end piece of equipment for line doubling to 480p and scaling up to HD resolutions. After playing with it since last night, I am impressed but at the same time dissapointed.

The CPO does a better job of dealing with the image overall than the CGA to VGA convertor (and so it should!). Assuming you have no SLG connected, the image is vibrant and sharper. The quality is not not and day imo over the CGA to VGA convertor, but it certainly is better. If you connect the SLG to both devices, the different is certainly less noticeable, to the point that is is negliable imo.

The CPO does a better job of handling the 30hz shadows.... they look artifact free to me, so the added benefit of the motion adaption engine shows it's worth.

However the biggest issue is the fact of the CPO working with the SLG3000 at 640x480 resolution. Obviously to achieve real scanlines on 480i or 240p games, you need to use this output resolution. Unfortunately the sync on the CPO is not the correct polarity, so you either get crap scanlines (flicker) or a dull image (SLG dip settings dependant). The only way round this is to whack up the output resolution on the CPO, which means you don't get the real proportion of scanlines from SLG on 480i or 240p material.

I know the CGA to VGA convertor is not perfect, but imo it is a better solution (if used with a SLG3000)..... certainly for what I want and need.

[Fudoh]

Doesn't the CPO allow you to set the sync polarity in the menu ?