Scavenge video encoder from Master System

[kendrick]

I fear electrocution at the back of a video tube. For that reason, I find myself more often needing to convert RGB to chroma/luma or to composite instead of the other way around. Yes, I'm aware of the safely enclosed, commercially available RGB monitors on the market, but I already have enough picture tubes in my house to set off geiger counters. Also, I can't lift as much as I used to.

Anyway, I'm building a SuperGun and rather than get an RGB-capable monitor, I'm planning to wimp out and just hook it up to the composite TV port. Is there any technical reason why I couldn't rip the video encoder out of one of my spare game consoles and redirect the RGB signals from the Jamma board into that? I only ask about the Master System specifically because I happen to have a half-dozen of them lying around. But if there's a better candidate for reclaiming such a part, I'm all ears too.

-KKC, who will bankrupt himself buying Mega CD games and CPS2 boards. How come Xmen vs. Streetfighter boards from Japan are so rare?

[kendrick]

Well, just so you don't think I'm a complete moron... I found out that the encoder in the Master System is a Motorola MC1377, which I gather is considered a relatively low-end encoder. Definitely not in league with the mighty Sony CXA chips, but possibly usable for MVS board output? Some experimentation is definitely called for.

Oh, it's worth mentioning... Thank the gods that the Jamma spec calls for the sync signal to be a separate pin, instead of included on the green line. Not that it's hard to do, but I don't want to have to build the circuit to separate the sync signal just to feed it into the chip to get reintegrated into the composite signal. I can only make my stuff so complex before I burn myself on the soldering iron, give up and then spend money.

-KKC, who is saving his pennies to give to Lawrence. He's a good dancer. :)

[phreak97]

some master systems have cxa chips.. at least some master system2's do.. my friends girlfriends does. mine doesnt however.

[kendrick]

Didn't know that, thanks. The four Master Systems I have in my house are all the first variety though, so I imagine that I'm stuck with the Motorola. Or maybe I should just open them all up and have a looksee. Weekend project!

-KKC, recoiling at the thought of having to enter Radio Shack and ask clueless salespeople for voltage regulators. "I'm sorry, I don't understand your question. Would you like to buy a phone?

[Endymion]

I fear electrocution at the back of a video tube. For that reason, I find myself more often needing to convert RGB to chroma/luma or to composite instead of the other way around.

Wait a sec--does this mean you have an RGB monitor? An arcade unit perhaps? Why do you fear it? Just learn what not to touch, and build your own enclosure? What is it you're using presently?

[kendrick]

I don't have an RGB monitor, but I am presently using a pretty high-end Sony TV to display my games. It does everything but RGB, and it was made before 1998 so it's free from the usual quality problems you find in Sony picture tubes. The only thing I can't connect is a Jamma board or anything else that does only RGB output.

The main reason I fear the exposed picture tube is because I lack perspective vision. I'm blind in an eye, and so I have tremendous difficulty judging relative distances in close quarters. I frequently reach for doorknobs and miss, I hit my head on too many things for a short guy, and it takes me three times as long as the next person to solder anything together. And man, if you heard some of my ex-girlfriends complain... :)

But seriously, I understand intellectually that it's simple to discharge an exposed picture tube element with a screwdriver and a ground strap. All the same, I don't trust myself not to touch the wrong thing. If both my eyes worked and my color sense were fully functional, RGB would be just as important to me as it is to most hardcore gamers.

-KKC, who missed buying an MV-1C board by THAT much.

[Endymion]

So, in your OP, you referred to adapting the screen to work with an RGB signal? That's a fool's errand as has been discussed here before. It is possible, but not likely without a lot of skill and possibly some technical information that your TV maufacturer just won't hand to you (hence the need for more skill/knowledge in these matters), you should look at the jrok and other encoders as they're a pretty easy ready-made solution. Working with a SCART box (+/- 5 bucks on ebay) it should be a pretty short project to deal with for optimal results.

[kendrick]

No no, not trying to shoehorn RGB input into a regular TV. That way lies madness and death. Just trying to downsample the RGB output of a Neo Geo MVS board into something that any composite input will accept. Ideally, I want to make the MVS board accept a wall wart power supply and have regular RCA jacks on the side so I can still plug it into a Jamma harness at some distant, fantastic future point.

Well, I finally pulled apart one of my spare SMS machines. Guess what? It's got the Sony CXA1145 chip in it. I spent all afternoon printing out the wrong spec sheets. Dammit. On the other hand, I know for sure that this chip will do what I want at the resolutions that the Neo Geo board can produce, so now all I have to do is find an MVS board. Dammit.

-KKC, who wonders if there's any value to keeping one of each of the SMS variants just for completists sake.

[viletim!]

kendrick,
I did the same thing myself when I was after a video encoder for my tv test pattern generator (link). I used a master system 2 which had the CXA1145 inside. It's not the best encoder around but it'll do the job. It's a step up from the MC1377 at least.

[Adeptus]

Anyone have a spare CXA1145, with or without console wrapped around it?
I'm actually looking to build a shoestring-budget Supergun myself... picked up a Mortal Kombat board for the cost of postage! B)

[phreak97]

i'm willing to bet i've got one somewhere if you want to make me an offer, i wouldnt ask much for it. i might have more than one if youre lucky. though they might be surface mount ones.. im not sure. if they are i can solder them down to a bit of perf board for you no problem, that way you dont have to worry about any crazy soldering. (charges may apply:P)
just had a look, i have a 1645M here, and at least another one in the other room still attached to a fried saturn. i dont remember if the 1645 is better or worse than the 1145, but theyre pin compatable as far as i remember, so itll probably do the job. im sure someone can tell us the differences.
anyone?

[Adeptus]

Cool thanks Phreak
(and I'll take you up on the soldering offer! Imperfect depth perception sucks...)

[viletim!]

phreak97,
The major difference between the two is that one requires more external components than the other. The 1645 is an improved and more integrated version of the 1145. And as fas as I know the 1645 is only available in a surface mount package.

[Adeptus]

In that case... I'll have a 1645 please Phreak!  

[ConsoleFun]

I found out that the N-PAL converter (aka. PAL Booster) for the PlayStation has a CXA1645 inside..

N-PAL PCB post

Cheers..

CF

[Adeptus]

So, it takes RGB + sync in from the PSX?
And outputs composite?

Sounds like a perfect Supergun component... just cut the cable & rewire it (or put a PSX A/V connector on your SG )

AU$20.50 shipped... if all that's involved is cutting the cable, then I'm buying one...

[Computolio]

   Did they ever make an NTSC Booster, or is there a way to switch this thing to NTSC?

[kendrick]

Theoretically, all you need to do is switch the input on pin 7 of the chip. Apply ground if you want PAL-timed output, or +5V if you want NTSC-timed output. Unfortunately, pin 6 is a 'subcarrier input' that I don't completely understand, but which may also use a crystal oscillator that could also need replacement. So on the surface, it seems relatively easy to switch this puppy to NTSC.

Anybody with better knowledge of the subject is welcome to correct me. I shouldn't be posting at 7 in the morning anyway. :)

-KKC, who never knew there was so much porn for the Super Nintendo...

[phreak97]

lol i have a spare pal booster aswel:P
i still have those 1645's spare if anyone wants them, and ill still attach them to a pcb for a little extra, not too much.

the subcarrier is the frequency of the video carrier for composite/svideo. it's not just a matter of high or low, you have to put a crystal on there, and a couple of extra components aswel. i can help out with that if you need me to, i've done it in my megadrive to keep colour no matter the refresh rate.