RGB to S-Video Adaptor

[Charlie]

Hello all,
After a few false-starts and some most helpful advice -Thank You!- here's a little something to expand video connection options for the CPC (and other retro boxes).


Of course Bryce has already made such a board for the Wiki - I guess the choice for prospective builders will be down to component availability.


-Prototype Board-

The input & output headers above are cut-down IC sockets. This is a bit of a bodge for the sake of easy testing, directly soldering in or proper sockets would be much better.


This board should work with anything that can provide the required signals: R+G+B+Sync+Gnd+5v


Why?
S-Video isn't going to be quite as good as RGB->SCART but it isn't half bad and what if SCART isn't a viable option? The board can be configured for PAL or NTSC.


Here's a few example photos, taken with a rubbish camera I'm afraid:


-6128 Sitting on unusual plinth-



-Close-up of CPC screen-



-Chukie Egg Pro Edition on BBC Master-



-Extreme Close Up thumbnail. LARGE IMAGE-




Should anyone wish to make one the latest version of the PCB layout can be found among the
project pages of my web-site (see link in sig) along with more detail.


I hope this proves useful to someone...

[Charlie]

P.S.
If you don't like / want S-Video the output header has Composite Video too!

[Bryce]

Hi Charlie,
       as previously suspected, the AD 724 seems to produce a better picture than the older MC 1377 and the MC 1377 is also getting difficult to source these days, so I wouldn't consider your circuit as an alternative, rather a modern and upgraded version of mine. As soon as I can get my hands on an AD 724 I'll be making one of these to replace my RGB to Composite circuit

Bryce.

[Charlie]

 
The board layout is 'published' as a .pdf ready for printing. I'm afraid I made this one in ExpressPCB but if the original file is of any use to you..?
I can imagine some of my choices over the layout (not very experienced) may not be ideal. (Or maybe a fully SMT version?)

[arnoldemu]

Of course Bryce has already made such a board for the Wiki - I guess the choice for prospective builders will be down to component availability.

I hope this proves useful to someone...

I think any hardware even if it's an alternative design is welcome.

So what plans do you have next?

[redbox]

That's pretty rocking, thanks for posting the photos.


I was wondering if it would be possible to steal components from a broken GX4000[nb]not that I have one, of course  [/nb] to make a better one of these boards?

[Bryce]

@Redbox: The circuit used to create the video signals in the GX4000 is much more complicated than the AD724 design and uses a CXA1145 (also obsolete these days). It would be possible, but not very practical. The AD 724 circuit is a very clean and simple design that gives a great result. What more could you want?

@Charlie: Thanks for the offer, but I'll probably just do my own layout, due to it's size it shouldn't take more than a half hour or so. Your layout may not be "ideal", but it doesn't seem to have any mistakes that would be detremental to the signal quality or anything though, so if anybody does intend using it, it should be fine. I will probably go for complete SMD design, so that I can put it inside my V2V

Bryce.

[redbox]

The AD 724 circuit is a very clean and simple design that gives a great result. What more could you want?

So is using this circuit means it much more likely to work with newer LCD TVs than by just using a straight SCART lead like this one on eBay?

[Bryce]

Yes, a true composite signal (as this circuit delivers) is guaranteed to work on any LCD / Plasma TV. The SCART cable will have problems on some modern TVs depending on how strict the TV manufacturer adhered to the SCART protocol.

Bryce.

[Charlie]

Thanks for the kind words chaps.


The next thing I have in development is a (hopefully) universal PS2->Quadrature mouse adaptor - possibly not much use for CPC's though...


It's quite possible this is already well-known to everyone here but me. The connections for the RGB port on the back of the 6128's PCB weren't as obvious as I expected...


Here's what I doped-out:




In case it's of some use to others.

[Bryce]

Hi Charlie,
           I don't know what the interface to the Quadrature is for your mouse project, but I have done a CPC PS/2 Mouse adapter that can also take USB mice and auto-detects what type of mouse is connected, if this is any use to you (it may be simple to adapt to the Quadrature?) then let me know (send me a PM) and I can give you some more info. You can check out the details here: http://www.cpcwiki.eu/index.php/PS2Mouse

Bryce.

[redbox]

http://www.cpcwiki.eu/index.php/PS2Mouse

Not only is this a great project, it's also a superb wiki page too 

[Charlie]

Yes, I have a fairly ambitious road-map of mods for my 6128 - Bryce's projects are pretty high on the list of plans...


...as an aside does anyone know if Yarek is still taking orders to do his 4Mb upgrade? May be safer for my CPC in the hands of a more expert person than me.


So here's my first CPC mod:



The hole for the 12v cable seemed like a good / solid place to mount the S-Video connector...
...my CPC won't have a 3" drive for long so the cable will be redundant shortly. I can always replace the 5v socket with a 3-pole socket for 5+12v if I change my mind.


It's not as 'pretty' as I'd like, but nice 'n strong - if the S-Video standard does have a failing it's how stiff the connection has to be to work: Puts a lot of strain on surrounding plastic.
If I get fed up looking @ this bodge I'll properly build up the plastic on the inside for internal / factory look. Maybe a composite connector would be easier, but possibly @ the cost of ultimate quality. 


P.S.
I seem to be getting a little power-rail type interference. Really only noticeable with very large blocks of colour...
...I wonder if bridging the power rails with a nice meaty electrolytic cap +/- a tantalum one) would  help..?

[Bryce]

If you haven't done it already, then stick a 100µf electrolytic capacitor across the 5V where they connect to the board and a 100nf ceramic capacitor across the power pins of the AD 724 as close as possible to the IC. If this doesn't resolve the problem, then it's not a power rail issue, it's the typical refresh ripple that tends to mess up the picture when you convert RGB to composite (much worse on the MC1377) and there's not a lot you can do about it

Bryce.

[Charlie]

Thanks for that...
...220uF cap across the motherboard power rails (I didn't have a spare 100uF to hand) and all fringing has gone!


I'd swear the output is now 'cleaner' than my BBC Master attached to the same TV via SCART.


The Mk2 is nearly ready - even smaller and more neatly laid out + one fewer caps. (I'll need to test output quality before release)

[Bryce]

Good to hear it worked out, 220µf is fine too, but for the final design I'd stick with 100µf (also because it's physically smaller too). Now I'm really eager to get my hands on an AD 724 but I've only found one supplier here and they want almost 15€ for one!! How much do they cost in the UK?

Bryce.

[ultrasyd]

Hello guys,
I've been lurking on CPC Wiki for quite a long time, but now i think it's time to register : ) Thank you for all the amazing projects and new developments, that's great. Sadly, this is not easy for a newbie like me, for anything concerning electronics.
I've been looking for a device that would permit to hook up my CPC with a very small LCD TV with composite video.
I saw the Bryce's LCD and Plasma TV solution, and now this thread, and it's very interesting. A little box powered by the cpc and able to send S-Video or cinch connector would be perfect.
I'm wondering if any of you can offer to build such a device ? Yes, no, maybe ? It would be very useful to me, as i fear that starting such a project is far beyond my capacities, not only due to lack of time : )
Thank you for your answer, and keep up the good job.

[Charlie]

Hello ultrasyd,
I hope you enjoy your time here - I'm pretty new to the CPCWiki and have to say I've been made to feel most welcome.


Thoughts on home-made projects:


For myself (like you) life is very busy, I would hate to offer to construct stuff only to let people down. A recipe for making myself very unpopular - sorry.


On a more positive front I'm in no way a hardware guy (more of a butcher) and my soldering is frankly pretty poor. I've got as far as I have because of my sad obsession with 32bit Acorns - if I don't make it myself it probably won't happen.
So armed with that necessity + Youtube + some cheap/rubbish equipment I went and took the plunge...
-El-Cheapo soldering iron + lead-solder + FLUX PEN(s) (+ hobbyists heat tool*)
-Practice soldering with some old PC stuff
Then
-Get some Press 'n Peel + 'Copper-clad PCB boards' + Ferric chloride granules + Acetone + steel wool + access to a laser printer + some designs + small drill + carbide drill bits
You'll have everything you need to make your own boards from scratch - it really isn't hard!


(Almost) everything you need can be found on eBay and if you're stuck I can point you in the direction of a few other useful sites.


*optional for SMT stuff: A bit like a small, very hot, hair-dryer. £10.00 for one or £450.00 for a proper SMT rework station? Hmm... let me think about that one!


PS
The above list is the bare (cheap) minimum - a good soldering iron is a big help & DON'T FORGET TO GET SOME FLUX!


PPS
I tend to make PCBs in batches when 'her indoors' is out of the house. (nasty stuff ferric chloride)  Having practised a bit give me a PM - I have a spare PCB for this project, drilled & ready for components, if you like.


PPPS
Might I invite you to take a look @ the projects on 'my' website (see sig)? Once past my odd literary style see what can be done, even if like me, you're pretty clueless. There's a couple of 'how-too's' in there.


All the best,

[ultrasyd]

Thank you for your answer Charlie ; ) I sent you a PM.
I can do little soldering and follow basic schematics but making PCB is really impossible for me... well, nothing is really impossible i know : ) But that would mean learn all the basics and buy tools, and let down many projects i've got to finish first.
It would be great if you could provide the PCB !

I'm going to check all the things you said for making boards... maybe i could give a try someday. I really feel like you can do everything when you can deal with electronics.

Going to check your website now !

[robcfg]

Hey Charlie,


Your are not the only one obsessed with 32-bit Acorn machines 


I have an Archimedes A3010, an A3020, a A7000+ and a 233Mhz StrongArm RiscPC.


Feel free to send me a PM or start a post in the Other Retro thread for some Acorn chat.

[Charlie]

Ah, that's a nice collection of Arc's...
...will start a thread.

[Bryce]

Hi all,
      I've built an AD724 based converter too now (thanks to Charlies kind IC donation) and I can confirm that the picture quality is 1000 times better than the MC1377 based solution. No ripples, flickers or other artifacts to be seen, mode 2 is perfectly clear and readable and even dithered colours don't have that funny rippling seen on the MC1377 converter. I went for an almost complete SMD layout, just cos I happened to have the parts here, other than the sockets and the crystal. If anyone wants the layout files let me know.

@Charlie: Do you intend doing a Wiki page for the converter? If so I will add the layout there when it's done.

Bryce.

Here's what mine looks like:

[Gryzor]

Man, you should start a regular production line with subscription packages for us punters

[Bryce]

If only I had the time. If I win the Lottery and quit my job, I'll let you know...

Bryce.

[Gryzor]

Cool, I'll just have to wait some then.