Amstrad Mega PC running Mega CD games

Hi there! I got reccomended to post here and show around what I did a while ago.

As you already guessed from the title I found a way to hook the Mega CD Model 1 up to my Amstrad Mega PC. I used a modified import adapter and the setup is a nice mess, everything fits just barely together.
I used this quick solution for basic testing because I've never seen any kind of material or info of the Mega PC and Mega CD running together. Sure enough it worked and it was really cool to see those two beasts running.
I want to build a cable sometime so it can be used with the systems just sitting next to each other, like you'd expect them to be but I'm not entirely sure how to.

Anyways, enough with the reading. Take a look at the video I made. It's much more interesting then anything I could possibly write here.

http://www.youtube.com/watch?v=3WxHOjfIt14

 

Very nice! Well done! How is the image in RGB? That will be a question a few might ask......

 

RGB? Well that's the only thing the system can put out, it only has the VGA output. Since it's 15khz only very few monitors are able to accept the signal. The image on the Amstrad monitor is pretty good, very clear colors without any problems. Of course it's only an old 14" tube and contrast, brightnes and the size obviously can't be compared to modern devices. I'm going to get a scan converter soon so I can use it on anything that has VGA, so I can hook it up to my TV.

 

I actually want to get one of the mega drive ISA cards from a mega pc. The ISA slot is pretty much just providing power, so you should be able to run the thing "stand alone" with some wiring.

 

^ the md card also doubles as an Adlib for the pc side... also there is a ribbon going from the md card to the mobo, that ribbon carried the 15khz signal and the signal to "power on/off" the md card. It is possible to install the card in another pc but except from the ribbon pinout one should heavily modify the host case to accommodate the card with it's cart/pads connections that are on a separate pcb that forms a T shape...
I had one and I thought about it at some point but IMHO it does not offer anything more than a normal md, the video output is still 15khz and the needed hacking does not justify the hassle...

 

i think half the fun is just showing it can be done, regardless of time and hassle etc.

 

Where is your sense of adventure?

Also, they apparently do not suffer from jailbars and have the best quality (I say apparently, as that is from a forum post somewhere - not personal experience).

 

You're right on the jailbars. The Mega PC doesn't have that problem, unlike all the other MD hardware I have and use with Scart on my TV. Since it doesn't have composite on VGA and syncs better the image is as good as it can possibly get. That's why I want to get a converter and use it on my TV, I absolutely can't stand the jailbars. Well nobody could on 55".

I want point out that the sound on the Mega PC is a little bit strange. The ISA card has a 315-5487 and so it's similar to some Model 2's. Fortunately the sound is actually quite good, mostly on par with good Model 1's but much louder. It's definately the loudest MD version I heard. There is some noise creeping in that reacts to what's on screen but not too bad since other MDs tend to have that aswell. What's weird though is that the PSG is REALLY loud, noticeably louder then FM wich makes some songs and sound effects sound quite confusing. I actually like the PSG a little louder then the typical MDs do it but the Mega PC just does it TOO loud.

 

That is so cool. I want to get one of those Megadrive ISA cards and a model 1 CD drive. Stick it into an old Windows 95 or 98 machine that still has the ISA slots and make the CD drive into a 5.25 drive to stick into a free bay. Also make a 3.5 drive adapter for carts. That would make for a cool looking slightly more modern Mega PC. Maybe even add a 32X in the mix for the fun of it. Region free modes, ect...

As for the cable to connect your setup, the cart slot for the Cd attachment is 60 pins just like the old Famicoms. You can use a cart slot and adapter or cheap game to make the cable. Floppy drive cable should be the best choice. They are 34 wires each. Just my 2 cents for ya man. You have me green with envy. :excitement:

 

That would be quite an ambitious project but a really cool thing, especially if it would be in a black case. But of course the parts for that system are rare and make the project expensive. A region mod on the ISA card would definately be nice.

As for the cable, I thought about splitting the adapter I used in the video in half and then solder an IDE or FDD cable to it. I need to take the protective coating on the PCB off tough, not sure how to do that yet.
I heard that the wiring for a cable like that has to be pretty short (about 15 cm / 6 in) and it needs shielding but I don't know if it's really that limited.

Could you show me, what adapter you mean? I've seen those Famicom to NES converters that are hidden ins some carts, do you mean on of these?

 

heh, glad to see many adventurers, just don't forget to take pics on the hacking/slashing

regarding jailbars , you can mod your sms1/md1 machines to use c-sync instead of compisite on RGB and the jailbars go away... I have done that in both my consoles and the difference is huge

 

I did some more thinking about the cable mod. It would be easier to just mod the expansion adapter on the CD side. It is a female to female plug. Split the board and go from there. I would cut the board down all the way to the connector and solder directly to the pins. Scraping the protective coating off is easy with light pressure from a slightly dull knife.

I'm not sure on the cable length limit. The Demo System DS16 has a long cable from the dummy cart to the changer and it is a standard ribbon cable. Seems to be 2 foot to me. No signal problems there.

As for the Famicom to NES converters, here's some pictures:

NES cart to Famicom


Famicom cart to NES.

 

I know about that double sided connection thing in the Mega CD but I would never think to cut one of these. I don't want to mess up the system, Model 1 Mega CDs are rare and the whole purpous of a cable would be to connect the systems without modifications on them. The Famicom adapter would be a good thing for both ends if the pins are the same width. It would eliminate the need of careful insertion because I had to place the adapter I used VERY carefully so the pins were all aligned.

 

Pin spacing is the same. Hell the pin spacing of all those old things is the same. NES, Famicom, ISA slot, Megadrive, ect. The pin spacing is the same on them. The only difference is the pin count. Since the Famicom and the Mega CD connection share the same pin count it is the way to go. That way the only way to mess up then would be to turn the connector 180 degrees.

For the sake of making it look halfway decent I would just remove the double female connector from the CD unit and get 2 Famicom cart slots from adapters or wherever and solder the extension cables to that.

If you need someone to do it for ya, I'm open. I have enough soldering experience to pull this off without any issues.

 

I think I'll try around with the import adapter for now since I have all the stuff I need here already. If that somehow turns out bad (or good and I want to make a nicer one) I'll look for alternatives.

Going back to the jailbars again, I already messed around with one of my RGB cables to use C-Sync instead of the composite crap but the TVs here then didn't show any picture. I think the sync line has to be buffered by a capacitor, at least some diagrams include one. Or isn't the C-Sync signal correctly fed to the connectors on the MD side? I always though it was but I may be wrong. It would be nice if you could explain a little on this, kerpoi. It would go off topic but I'd appreciate it.

 

Yeah I did not get any picture too by simply modding the cable... see the pinout posted here



what I did is to completely disconnect any signal going to pin1 on the av port, on the md1 you just lift an easy to find nearby diode (just trace from the av port) and it is cut off completely. Then just connect pin11 of the Sony rgb-amp to the pin via a 220mf+75ohm resistor and you get a vastly improved picture

Below is a pic I found from an old sms1 mod I did



it's pretty simple once you disconnect pin1 from any signal

 

Love it! And of course welcome to the forums! :congratulatory:

 

Thanks for the welcome RetroJunkie and thanks keropi for that explanation on how to get the propper sync signal.
The mod inside the system worked although I had to use a rewired cable because with the other one it always took the composite signal to sync.
The jailbars didn't go away completely but to about 80-90%. I see them faintly in some darker colours like brown and even black, but really just very faint. They are gone on blue where they used to be annoying so the image is a lot better.

But there is a bad thing. My TV just has problems with the sync signal that the MD outputs. The image makes about a 1/4 screen high jump every half second. The weirdest thing about this is, that there are some exeptions like a title screen here and there where the image stays on screen just fine. I tried doubling and trippling the capacitor but that didn't change anything. I tried a stronger resistor and the the image changed from jumping to constant rolling.

It works fine on my mothers CRT but my HDTV refuses to take the MD without composite for the syncing. I think it lost the ability to properly sync on a real sync signal some time ago. I remember that the MD1 RGB cable gave me jailbars while the MD2 didn't and it worked fine. Then one day I hooked everything up again after not playing for a few weeks and then the TV started to have the strange behaviour with the MD2 it now has with the modified MD1 to use c-sync. I really think that something inside the TV got messed up back then.

Sorry to take the topic so far to the jailbars but the whole story just annoys the hell out of me. As for the construction of the cable, I hate to say that I can't seem to do it, at least not with the 40 pin IDE cable I wanted to use. I couldn't properly take off the insulation without ruining the cable in the end. The tools I have here are just not good enough to properly do what I want to. I cut the import adapter in half, that part worked but then I gave up.

I came up with another plan that is propably the easiest but also more expensive and not flexible to use. With four of those passive import adapters stacked together and the last one modified to 30 pins it should easily be possible to connect the Mega CD 2 to the Mega PC in an L-shape without blocking the controller ports. The question would be, if a extension of that lenght would work and I think only testing can tell...

 

Sorry to hear about the sync troubles CobaltBlue , is your lcd tv by any chance a Samsung? They are notorious with scart/sync problems...

 

I have a Toshiba 55SV685D though coincedentianly it has a Samsung Panel inside. What bugs me about it is that it used to work but then it stopped out of nothing. Now I have to chose between jumping image and jailbars but at least the latter one works and so does everything else on that TV.
Well, I wanted to get a CGA2VGA for the Mega PC anyway and I guess I'll also buy a Sync Strike so I can hook everything up to the VGA input.