Help! Sega Master System 2 RGB mod - no Sony chip?

Or just program a replacement bios? its just a 27c256 or 27c512 iirc

 

Which pin is the composite pin for that chip?
I remember assuming that the sync pin was composite when I did it, it didn't turn out so well.
I notice on these machines that even the RF has pretty bad ghosting.
On the older SMS2 machines with the sony chip, you can grab the composite from where it goes into the RF box and it gives a nice clean signal as a plain composite output and as the RGB sync.

 

Ah well, at the time it was "why the f&*k would someone do that?" "You know what? I don't want to know in case it makes sense". (I gave up years ago wanting to know why people do shit).

I just wanted to know if it would work, which it does so it was a case of just put it back together.

Pin 20 is the composite pin.

The only pin I haven't connected is C-sync as I am using composite for syncing. It works fine through the RGB-component converter, I likes it.

To use C-sync on these guys (ie SMS2) you can't just tap off C-sync. I remember reading somewhere else (Viletim was involved, I remember that) that you do need additional components. I guess you could refer to the SMS model 1 circuit and implement that but on the SMS model 1 it is actually taped of C-sync IN on the video encoder.

 

I used C-sync for the RGB without any issues, I probably used the 75ohm resistor and 220uf cap but I'm a bit snowed under right at this moment so I won't have time to open it up and have a look for a while.

 

Progress - implemented the RGB and 60Hz mods and in the first round of testing.. there is no sound. Probably something simple so i'll take a look at that. A couple more troubling issues though:

Quite a lot of .. crosstalk (?) on the colours. Not bleeding in a normal sense, the colours are crisp and the picture is sharp and bright. It has Sonic built in, so say on the blue background on the first level, where there are three yellow rings in the picture, in the horizontal lines that they occupy, the blue will be very slightly darker. So I have horizontal bands of slight colour interference, even though the picture is pixel-crisp. Any ideas? It *could* be the cable I'm using as I haven't tested it with any other consoles yet. It's a Master System 1 / Mega Drive 1 RGB cable bought new from eBay.

Secondly with the 60hz mod, there is a shit-load of slowdown in places. i.e. the framerate drops dramatically. Does the console need an overclock? There doesn't seem to be a lot of info on this.

Thanks guys

edit Sound rectified, just plain had it on the wrong trace. Still having the other two problems though.

 

Can't overclock SMS, they go nuts.

It has been covered (I am sure) on smspower.

 

Yeah seems like you can't do it without it screwing with the sound etc. I'm happy with the mod overall, made a clean job of it i think. The colour interference is going to bug me, though. Still, the difference between washed out, fuzzy, slow, squashed 50hz RF and 60hz RGB is night and day. I've been reading about the choppiness with sonic at 60hz and apparently it's just the way it is. Having a hard time believing that a stock NTSC console would suffer in the same way though, it's really noticeable to me. That said I'm a frame-rate freak, a lot of people don't notice the same slowdown on some 360 and PS3 games that I find unbearable.

 

I might end up importing an American mark 1 SMS at some point. Same goes for MegaDrive / Genesis.

 

The RGB cable for MS1/MD1 has the resistors and coupling capacitors built in. If you put those components into the MS2 when you did the mod, you now have two capacitors in series with the video signals, and it'll all be out of whack.

Incorrect coupling cap values causes banding like you describe.

 

You, sir, are my favourite person on the internet tonight. I was really hoping someone would know what I was talking about with the banding (now added to my vocabulary). I thought the point of mmmonkey's mod was to be able to use these cables, so why he put the capacitors in there I don't know? I understood that the cable had resistors built in, but not the capacitors.

Too late to look at it now but I'll have a go at running straight from the chip to the din socket tomorrow and report back. If this is the case then i'm kind of miffed that I walked halfway across the city for the capacitors and built the vero board for nothing

All part of the fun. Thanks for the reply.

 

I don't personally think mmmonkey is the most technically inclined person. His way isn't always the best way, that's for certain.

 

My pleasure!

Check this page out: http://members.optusnet.com.au/eviltim/gamescart/gamescart.htm

It describes how the video encoder chip is connected to the AV-out socket on various consoles, and what the AV cables should contain.

The guide that mmmonkey based his mod on (which is mirrored here) is designed to have a SCART lead attached directly to it, hence the components. In essence, mmmonkey's MS2 RGB mod is wrong.

Tru dat!

No worries!

 

RE slowdown, might be the case where you're pushing a faster refresh rate which is taxing the hardware a bit more if you're playingf a PAL title.

I remember back in the day when I first added a 50/60hz switch to my Saturn (which was... in 1999 IIRC) that I was surprised by the slowdown on some titles that weren't apparent when pushing at a lower framerate (Marvel Super Heroes in particular was quite noticeable on 60hz!).

 

Ah hadn't considered the double up of capacitors. I orginally had the caps in the SMS2 but since referring to the Sega manuals no caps are present in the console so I removed them and have ordered some small (physically) 220uF caps to put into the scart cables (as they are missing).

I think if you really want a SMS2 with RGB with no effort, just get a french one (no RF but RGB socket).

 

So I cut the capacitors from the board (rendering them pretty useless in the process) and simply joined the tracks together on the vero board. The picture is terrible, now. Very dark and the banding is much, much worse. The colours are all over the place. In comparison, the picture before was excellent with only slight darkening of the blue background in places. I thought maybe the messy vero board was causing the problem so I cut the cables away from it and joined them together with the exact same results. What on earth is going on? The wires are going straight from the chip to the DIN socket, straight into this cable - http://www.ebay.co.uk/itm/261180150983

 

Very weird!

Do you have a multimeter? I'd be checking the cable, to make sure it has been correctly made.

 

I don't recall off hand which does what between the capacitors and resistors but I'm guessing you have too much resistance going on there. I'm having a hard time telling what exactly you've done so far but I'm going to point a finger at the SCART cable having resistors inside you aren't currently aware of.

 

Tell me about it. I don't have one, I was very close to picking one up in a shop the other day, not sure why I didn't.

All I've done so far is follow mmmonkey's mod to the letter, albeit with the previously mentioned video chip, and then scrap it and connect the pins straight up to the din socket for the ms1/md1 cable. I don't have anything else to try the cable with, though I do have a mark 1 mega drive on the way from ebay. In the meantime I will assume that I'm the problem and not the cable. Though I've checked over all my solder joins on the pins and they look clean. (Which is surprising, because they are tiny and I was loaded at the time.)

 

I agree with this. strip the SCART plug back and have a gandar.

It may be picture time....

If you can take a pic and edit it in paint (or the like) number each core of the wire from A to B (example 1 on the AV socket to 1 on the video encoder etc).

 

Ok - I'll get some pictures up tomorrow. Do you know if the components are likely to be in the scart plug end? Would seem a bit of a squeeze to get them in behind the DIN plug. I'm just really surprised that the quality took a dive when I removed the capacitors from the master system, when there must be the correct capacitors in the scart cable for it to be compatible with SMS1 and MD1.

Another thing is I don't know if I'm being too fussy here, especially with the first banding problem I was seeing. My Mega Drive 2 with RGB looks *fantastic* and I'm expecting the same kind of quality from the master system. Am I being too optimistic?

Thanks again for all of the help guys, I'd have probably given up by now if it weren't for you.