Thursday, 20 December 2012


Howdy pardnurs,

Well now that the Jamma fingerboard is securely attached to the Megadrive 2's PCB and it fits into the case with its new expansion port we'll move onto the wiring. Through the whole process I will keep dibbing away at finishing up the expansion port as I'm using milliput and it takes over night to cure really. So I add little bits here and there and allow them to cure without the chance of me poking them...cus I'll be asleep :-P

To start with I found a few guides on how to make Sega Megadrives into Jamma-drives and all had a similar starting process:
1) Tap the RGB, sync and ground from either the RGB encoder chip or the additional solder pads on the A/V connector under the PCB.
2) Tap the audio from the solder pad under the A/V connector.
3) Plug the Megadrive into the arcade machine / or Supergun's jamma harness with the normal Megadrive PSU and check that video and audio are working okay.

This allows you to problem solve any issues as you haven't made that many connections so far.

Seem's easy enough right. A few wires and your away. Well, thats kind of right.

I decided to solder directly to the RGB encoder chip as some people said that this may provide a stronger RGB signal. I googled the chip in my V01 megadrive 2 and found the pin-out and started trimming and tinning wires and soldering the sucker up.

Well what do you know?! I get picture!! But, the image seems to move, kind of clicks from one point to another and back again. Like its switching between either PAL / NTSC or aspect ratio. Also the biggest problem, there is horizontal bluring through the colours. Really distracting and causing weird colour clashes. Bugger!

The wiring is so simple where could the problem be?! I assumed that my soldering wasn't neat enough and i'd either bridged two of the suface mount points of the chip so I checked them out and they seemed fine. Hmmm. I unsoldered the wires and then looked up the A/V pinout for the port and wired to the solder pads underneath it. Maybe you can't wire to the chip?

I go upstairs and test and darn it! The same problem! This is frustrating!

I got a few more pinouts and did some google searches and couldn't find anything on the problem. Then it occured to me that its essentially the same as doing an RGB cable so maybe I need to add the 75ohm resistors and the 220uf capacitors?

I made up a little Vero board with the resistors and capacitors and wired it up to check. Same problem only this time its a little darker now as the resistors are lowering some of the signal strength. Stupid horizontal RGB blur!! Its a little harder to see in the Zombies photo but that mottling on the circles is caused by the blur and shouldn't be there.

Thinking that maybe the RGB encoder chip might be at fault I decided to make up an RGB Cable for the Megadrive 2. I'd been planning on doing one anyway and had the parts so I got soldering. Using the great guide from

Another test but with the Megadrive 2 hooked up as normal (no jamma) and the new RGB cable and BING, picture is perfect. Nice and sharp with bright colours. Awesome for the cable as that will be used on my other Megadrive 2 and Neptune but bugger because it shows that something is still up with the Jamma wiring.

Looking over the wiring guide for the RGB cable I noticed that its got Composite Video hooked up via the scart but no Sync. Comparing that with the Supergun wiring guide I noticed that the sync pin on the jamma board is hooked up via the Composite Video pin on the Superguns Scart port. Could it be that?!

I found the composite video solder pad on the A/V port area of the Megadrive 2 and moved my sync wire over to there. A quick test and WOOP! The video is perfect!! No horizontal blurring and everything looking like its using the RGB scart cable!

I know, it seems like such a simple and stupid problem to have with the A/V but when everyone says follow the Encoder pin-out and hook up the RGB Sync and Video ground as is rather than using Composite Video out for sync then your going to run into problems. This took me a week and a half of headscratching and fruitless searching to figure out haha. Yes Im that tentative with hooking wires up incase I blow something.

Now that the Video is sorted I hooked up the Mono Audio out from the A/V port area to the Jamma finger board and hooked the Audio ground up to the Jamma fingerboards ground. Thankfully this worked straight away and is super loud through my arcade speaker, so loud i might have to put a volume switch on haha.

Here you can see my testing setup with Zombies (ate my neighbours) running on the Jamma-drive 2 with the audio hooked up. Thank goodness that stage one is figured out!

The next step is to hook up two switches, one for the 50/60mhz PAL/NTSC mod and the other for the English / Japanese language mod. I followed the guide from again as I've used this mod on my other Megadrive 2 and it worked a treat!

My aim for doing this project was to try and keep my wiring as neat as I could. This is a problem though when your trouble shooting and having to hack up wires for testing. Its still fairly neat and easy to follow though.

Here you can see the points I soldered the wires too for the language and PAL/NTSC mods.

Pretty neat wire routing for me I think :-) and with this mod the hot glue is definetly needed as the points your soldering too are very small and you don't get much solder on there and its very easy to pull and break traces if the wires get snagged or pulled.

And here is my wiring up for the A/V parts of this project. I used some ribbon cable from an old DVD player to try and keep them more neat but the problem solving caused me to seperate the wires out doh. Still, its not too un-tidy I don't think.

Here is the view of the top of the Jamma fingerboard with the Red, Blue, Video ground and Mono Audio wired up. Actually looking again it looks pretty neat still. Once I've completed it the wires will be hot glued into place on the PCB and hopefully routed away from the voltage regulators heatsink as I think that might start to melt the wire casings if used for a long time.

And here you can see the underside of the Jamma-drive 2 with the wiring going to the solder points of the A/V port. Still not too messy and once I'm properly happy they will be hot glued into place to make sure they don't come pulled or anything. :-)

The orange wires are the power lines to the underside of the voltage regulator which are supplying the Megadrive 2 with +5v from the Supergun's arcade power supply so I no longer need to hook it up using the Sega power supply. The Jamma-drive 2 is now A/V and PSU cable free! :-D

Next up is hooking up the first joypad so that I can use my arcade sticks via the Supergun rather than a pad out of the front of the Megadrive.

Catch you later


Monday, 17 December 2012


Hi Everyone,

Yep that title is correct! A megadrive 2 that runs in an arcade via JAMMA connection! :-D

I've been eluding to it in the last few posts and seen's I've made a breakthrough with my A/V problem this morning I thought I'd post up the 1st part of my build of this unit.

Its nothing new really building a Jamma compatible megadrive, I'm certainly not the first to do it by any means but I've found a few little things out while building it that weren't really documented when I'd been doing research on them before I started soldering. Also I'm trying to do this Jamma drive a little differently to the others I've seen on the internet. The main difference being that it will be very nearly totally stealthy!! Most jammadrives I've seen have the Jamma fingerboard sticking out of the side of the casing which doesn't look too bad, but to me it won't look just right on the shelf with all the other consoles. So I've decided to make it hidden via a second expansion slot on the megadrives casing. Also I will be over-clocking it and doing the 50/60mhz and language mod's as well as having it power the Sega CD 2 all from the Supergun's power supply. So there won't be a big ol mess of cables everywhere.

Well thats the plan so lets start the progress photos and a bit of rambling. :-)

The first thing I did was scour the internet and read as many forum posts, watch youtube videos and read web-pages about creating the Jamma drive. Trying to get as much research in as possible so that it will run as smoothly as possible. There isn't that much info on doing the mod to a megadrive2 as there is for the megadrive 1, but it shouldn't be too hard to do. . . Also I re-printed the schematics I used for making my Supergun so I had the correct Jamma connections I used.

The next thing was ordering the Jamma fingerboard from ebay. I initially wanted to get the blue fingerboard a lot of the american's use but it was a bit hard to find so I opted for a very generic looking plain fingerboard from the UK. Nice and cheap and as long as you check against a schematic you should be fine.

While the fingerboard was on order I decided to start modifying my case so that I will get the stealthy look by hacking it up and trying to add in a new expansion port. As I have some spare megadrive2's around and I had a spare case from a megadrive2 I'd scoured for parts I decided that would be sacrificed for the cause.

I got my dremel out and amputated the right-hand sega-cd expansion port from it. Then I turned to the Jammadrive's case and dremelled out the space for the expansion port to go.

Here you can see the normal expansion port on the right and the new one that will be fitted on the left. I've had to cut the slot a fair bit wider for the Jamma connecter to fit inside the casing so it will reach the fingerboard. I will have to milliput some extra sides onto the port cover to make it all fit nicely together.

With a bit of electrical tape holding it together I tested out that the Jamma connector would fit into the case. With that double checked I set about milliputting and hot glueing the new port into the case.

Here you can see the port now milliputted with some hot glue 'tacking' sitting in the jammadrive2 case. Its nice and rigid and should handle the pressure you have to exert on the case to open the darn thing. Next is to extend the cover to make it meet the edges of the case so it looks all OG. ( sitting in the case in the left image is a Neptune button being re-milliputted, yep it's still going on haha)

While I'd been working on the casing the fingerboard turned up from ebay so I set about lining it up with the new expansion port and hot gluing and milliputting it into place so that it should stand up to the connecter being put on it. You don't want it pulling away from the motherboard when your trying to connect up the Supergun to it!! haha.

Here you can see I tried to place it inward enough so that the motherboard will take some of the load of the connector but not interfer with areas I will need to solder too. Once the milliput cured it really was stuck on there like rock! Brilliant!

And here's how the Jammadrive sits in its case. Pretty nicely I think!! :-D The fingerboard fits nicely in the gap down the left-hand side and seems to balance the megadrive out a bit now. Also I've extended the sides of the port cover so there are no gaps down the side now. There is some finishing up to do to the case but as I'm an eager beaver I will jump onto the soldering to make sure it is starting to work.

Next part : " The woe's of using multiple guides and information from the interwebs to do simple wiring. " haha


Wednesday, 12 December 2012


Hi All,

This post goes a little bit off the retro console track but more along the emulation route this time. A short-time ago I was looking eagerly at the new Neo-Geo X portable console thats coming out this christmas. It looks like quite a nice little handheld and I like the look of the AES style base and fullsize joystick. Unfortunetly the plastic doesn't look as good quality as used in the original AES. And I would ultimately love to have an AES over everything else still a geeky 12 year old in my head .

Anyway what the Neo-Geo X made me do was dig out my old PSP again. Mainly because I read that essentially the NG:X is emulating the games, so I thought why bother when I already have one of the nicest looking portables (in my opinion, it still looks stunning) that used to be able to play emulators.

I originally imported my PSP from japan so that I got the version that could be easily hackable to play 'homebrew' and emulators. And after playing through Vampire Saviour a load of times I got the eboots of the interwebs and got a load of emulators on it. Man that was brilliant! Having PC Engine, Neo Geo and Mega drive games on the go with a crispy glossy screen was great!

Unfortunetly for me I got Metal Gear solid for the PSP and you needed to update the firmware to play it. At that time, every firmware that came out they generally hacked it to bits within the first week so I though "what the hell!! I'll update and play this and in a week I'll have the emulators back! woop"......wrong!!! That was the firmware that caused a real problem and the soft-hacks no longer worked and they eventually found out you needed to use a Pandora battery to get the custom firmwares installed. I wasn't going to buy a new battery for my PSP so I had to stick to buying proper games and then It basically started gathering dust on the shelf.

Fast forward to a month ago and a curious google search. WHAT?! you can eboot the PSP again and play your emulators again on it!?!?! oh yes!! :-D

What I found was someone has made an eboot hack the same as the old way to do it called HEN or Half-Byte Loader. You basically upgrade your firmware to a more up to date version and then you get Half-Byte Loader from

You pop that into your PSP folder and your away!!! Occassionaly it doesn't load or crashes but if you get the trick to loading it your fine.

I couldn't be happier again!!! I've got Cave Story PSP and finally working my way through the game as I got stuck on the PC version a few years ago. Its an awesome game and works perfectly on the portable.

I finally got an Amiga emulator to work as well which has always flumaxed me in the past so I can play the games I used to own when I was at school. Complete nostalgia kick and has got me chatting some old school friends about the sundays where we used to have full on game days! :-D

And thankfully SCUMM still works so I can pick away at finally getting through Beneath a Steel Sky and The Dig.

So yeah, if you have a PSP that's gathering dust on your shelf, which to be honest is a real shame for such a good looking and playable console get the HBL on it and get some retro goodness on the go!!

Catch you later for hopefully a post on making a Jamma-Megadrive 2 which I'm in the process of doing. But I'm getting some issues with the RGB out at the minute which is causing some head scratching.

Catch you soon