Who's interested in having an S-Video Modulator?

[arnoldemu]

Hi. I´m rave_dj ...

Welcome to cpc wiki forums!

Your English is fine. I understood you well!

[al]

i really really really want a composite adaptor for my 6128! s-video and scart are very rare in australia!

[Bryce]

Hi al,
     the AD724 Modulator gives a very good S-Video picture, but a mediocre (typically crap) composite picture. There are several alternative ways to get a composite signal, the easiest being to convert an MP1/2 to composite output (if you have one of these).
More info here: http://www.cpcwiki.eu/index.php/LCD_And_Plasma_TV_Solution
If you don't have an MP1/2, there are further (less simple) solutions available. Register an account and send me a PM, then I can give you more details of all the conection methods.

Bryce.   

[RockRiver]

Hi!! Bryce and all...
Sorry if this is a little off topic.
That I want is the "vice versa" S-Video to RGB. Maybe I must write a new post about it.


My intention is to connect a commodore [ups!!, one of the eternal rivals] C64c (s-video able) to an Amstrad/Schneider CTM-644 monitor.
[But, mates, this is a CPC forum and CTM 644 is a CPC monitor  ]
In all Net I didn`t find anything about s-video to RGB.


Is impossible to make that or only crazy? 

[TotO]

Better to plug it on a CRT TV with S-Video IN.
Better display, better picture, and cheaper solution.

[TFM]

Of course. And no waste of Amstrad hardware

[Bryce]

Converting RGB+Sync to S-Video is simple, there are many ICs that do everything for you. Converting S-Video back to RGB is a completely different story and very complicated. There are devices that will do it for you, but you'll probably pay alot for them. Unfortunately none of the VIC II graphic chips output RGB anywhere, the picture is already converted to Colour / Luminance signals internally, so there's nowhere on the C64 PCB to acquire the RGB and sync signals you need.

Bryce.

[RockRiver]

I found that:

Composite S-Video to Video RGB Sync On Green Converter

Yes, expensive... and I would see inside of it (which ICs...)


And another questions:
Could I transform easy or connect RGsB to normal CTM-644 RGB and syncro?
I could solder Gs to Green and to Syncro pins of CTM connector and would work?   

[Bryce]

Unfortunately not. The output of this device is Component Video, not RGBS. This couldn't be connected to a CTM-644. As far as the ICs inside are concerned. There are no dedicated S-Video to RGB converter ICs, so I suspect there's an FPGA and a mixture of analogue ICs inside.

Bryce.

[RockRiver]

Thanks for answer, Bryce, but sorry, I think you are wrong... this device has RGsB out option too. It's a RGB option but with Sync + Green on same wire (a Sony invention ? ). My question is now about how to separate this Green & Sync junction.
Maybe CTM-644 is strong and I would connect Green+Sync from RGsB to Green and Sync pins on CTM, to both. Interference then on green?
Or maybe use a Sync separator ic as LM1881N 

[Bryce]

That's exactly what I said in different words The Sync is on the Green signal, so you can't connect it to a CTM644. You would need to seperate the Sync and this is also not an easy task. You would need a further (possibly expensive) device to do this. You could possibly do it by building one yourself using the LM1881, but the LM1881 is expecting a complete Composite video signal, so I have no idea how it would react when it just gets Green-Sync. It also only outputs the V-Sync signal, whereas the CTM needs a CSync signal (H+V Sync Combined).

Bryce.

[RockRiver]

Thanks Bryce for your answers...
I have the solution for C64 s-video on CTM644 -----> a second hand DVD recorder [s-video to RGB] Yeahhh!!!![size=78%] [/size]

[Bryce]

That will work, but isn't it rather large?

Bryce.

[Devilmarkus]

That will work, but isn't it rather large?

When you remove the C64, it isn't! 

[Munchausen]

I built this circuit on strip board and just couldn't get it to work. I was sure it was the capacitor value for the crystal but whatever I did I would just get a fuzzy black and white image.


I decided the problem might be that the strips in the strip board are providing too much latent capacitance - so I made them as short as possible, and still no luck.


At this point I gave up completely and built an RGB SCART cable, which works perfectly.


It was just after I got the SCART cable working that I realised what was going on. It was the latent capacitance in the strip board - but because the AD724 is surface mount I had mounted it on its own little daughter/breakout board, which I also made with strip board, and I forgot to cut the lines on there! Now it all works perfectly... and I guess I now have two options for connecting displays to my CPC!


So, for those that build this themselves on stripboard, beware: The traces attached to pin 3 where the oscillator connects must be as short as possible, so make sure not to have traces heading off to nowhere as is typical in strip/vero board circuits!

[Bryce]

Yes, the 4.7pf capacitance and the crystal tracks are critical. Anything that increases the capacitance in this area will cause the AD724 to start up improperly and give a pretty shit picture. I think you are the first to have made your own though

Bryce.

[Gryzor]

Well, look at his nick, for all we know this is a tall tale

[Munchausen]

Heh, well spotted. But no, it's true!


Maybe I'll post some pictures later, though it's all a bit messy - I accidentally broke off part of the board and had to solder the tracks back together, and the surface mount 'adapter' I built is also not ideal.. I made that bit around 10 years ago when I got a couple of AD724s as samples but never ended up using them.

[Gryzor]

Oh, we've seen plenty of messy boards here  Do show us!

[Munchausen]

Ok, here ya go...


You can see the crack in the strip board where I broke it, and also the hole in the 'daughter board' which I drilled to reduce the length of the track going to pin 3 (I couldn't be bothered to unsolder the whole thing, cut the track and put it back again).


It's only wired for composite, but it would be very simple to add s-video. I might make another couple at some point and will probably do a much better job next time (at least I'd hope so).


The wires going off to the left are the inputs (Sync, GND, R, G, B, in that order top to bottom), and the two wires going off towards the top of the photo from the left of the board are for power. In the second photo you can see there are a few components underneath the daughter board too, which saves some space.

I'll mount it inside my CPC when I find time.

EDIT: I just noticed these pictures are rather large to view in the forum... so you should click on them and then right click and hit view image to see them properly.

[Bryce]

For a strip board build it's very good, well built. But these type of circuits (frequency critical analogue circuits) definitely shouldn't be done on strip boards. You're just asking for trouble. Congratulations on getting it working though.

I didn't think anything of your Nickname, other than the fact that you possibly live in Munchausen? Besides, if you meant the Syndrom, you would have written it properly: Münchausen or Muenchausen.

Bryce.

[TFM]

... you would have written it properly: Münchausen or Muenchausen.


Nope   Münchhausen ;-)

http://de.wikipedia.org/wiki/Hieronymus_Carl_Friedrich_von_M%C3%BCnchhausen

[Bryce]

Oops, yeah, two Hs, it was actually the Umlaut that I meant And actually I think the place is spelt Munshausen anyway because it's Letzebuergesch, isn't it?

Bryce.

[TFM]

Dunno, just remember his name Münchhausen. Well, the crippling of the German spelling can't touch persons names at least *hehe*

[Munchausen]

Thanks for the positive comments

And yes, I've missed the umlaut and possibly otherwise misspelled it... TBH it's more a reference to the film that I watched as a kid as anything else.. as it happens the man for whom the film is named is also the source of the name for the condition. The film was amusing and therefore I thought the name was kind of funny, and then found that the man and his tall tales also seemed quite silly. And it's quite good as an interweb name because it's fairly different but not so different that you can find all my posts by searching for it!