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Core Grafx 1 RGB mod

Started by Midori, September 21, 2009, 05:13:13 PM

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I finally collected the guts to mod my Core Grafx PC Engine. The composite quality is fair for composite from 87 but it's still composite. I've read Lawrence's wiki part ( ) and mmmonkeys guide ( ) countless times and decided it was time to take action.

I'm not done yet but I have successfully tapped the RGB signals from the expansion bus and the other signal from the DIN port. One of the most difficult parts of modding the Core Grafx so far has been to choose a good RGB connector and mounting it. I usually use a DB9 connector with a pinout close to identical to the one Lawrence described here( ) but I thought that a DIN8 would be simpler to put in the Core Grafx... Turned out I was wrong.

It's pretty damn tight inside the Core Grafx :-)

I considered taking out the 5-Din connector but that wouldn't really helped since the hole for that one is almost too big for a usual DIN8 connector to sit good. I choose to install the DB9 instead and found a tight corner to do that in(to the right of the DIN 5).

As I said I already have tapped the signals now but like most RGB docs for modding a PC Engine says the colors ain't very strong. So I am also going to build an amp, my design is already done( it's based on the japanese schematic on the PCE RGB wiki page) but I have to buy a few components to make it so I have not tested it yet. I noticed a few others on the board were a bit confused by it( here: ) and so was I. But after learning a few new bits about how to read schematics and the help of a friend I have something that is quite simple and easy to build( in my opinion) that can hopefully help others too.

... Although, as I said, I have to see if it works first ;-)

A pic of the poor Core Grafx in its current state:

Will hopefully have an update with a succesfully installed amp later. The thing I fear the most right now though is how to get the unit together again...


Arrgh, bad and good news. First the good ones. The amp works! Woho, I get a very nice picture with it. Perhaps not flawless but good, much better than the original RGB.

The bad one is... I can't close the Core Grafx any longer ;-) I guess I hoped for too much. The amp is just too big. Although I could get it a bit smaller at least.

I'll post my schematic of the amp I build.

I couldn't find 1815 transistors so I went for BC337s instead. They hade a different pinout so if someone likes both my schematic and 1815s' take heed.

This is the smallest I could get one of the amps(the real idea is of course to have all three amps on the same board):

The other two I built were slightly larger, but even if I Shrink them to this size it'll be a extremely tight fit, too tight.

I think I'll do so that I pick out the amps and build myself a small box for amplifying the signal for the PC Engine instead. Not the most pleasing idea but the most reasonable right now.


On the bright side, if your amp is external then you can use it for all your consoles that need it.


That is true. I still can't belive the amp didn't fit in the Core Grafx though. One day I will give it another go... On a different PC Engine though. I don't want to mess around more in this one.

I've now made the amp external, but have yet to put it in a nice box. Still have not found one... I can offer a pic of my Core Grafx though. So that all my fans can watch were I put the DB-9 ;-)

It looks a bit less neat up close but hardly my worst work.

For all that doesn't know and/or wants to see the difference I have taken a few shots for you of R-type with and without the amp:



I took two more(and better) pics of one of the enemy sprites up close



The same brightness, contrast and color levels on the TV for all the pics of course.

Now, where shall I find a nice box for my amp...


I have an idea, how about use a serial switchbox, with the same plug and pins you can turn this box (or any similar) into an on/off switch for your amp.


Well, that could be useful of course. But at the moment I only have my PC Engine that requires it so it would probably do little else than take up space.

Although one of those with five or so inputs instead, that would be useful! I could use it as a switchbox for all(or at least quite a few) of my RGB consoles, not having to switch cable every time would be comfortable :-)


Quote from: Midori on September 23, 2009, 05:49:08 AM
Although one of those with five or so inputs instead, that would be useful! I could use it as a switchbox for all(or at least quite a few) of my RGB consoles, not having to switch cable every time would be comfortable :-)

Here's a 4-port, I would not say switches with more ports do not exist but I don't know where to find one.


Extremely late answer but thanks! That looks quite interesting. Although, you are perhaps not aware of this but i live in Europe, Sweden. :-)

But those kind of switch boxes probably exist around here too... Will have to check around.

I  have mounted the amp in a small box now by the way, to conclude this adventure. It didn't turn out very nice though. I just grabbed whatever was closest to me. And the result is a sturdy construction but not a very pretty one ;o) If I take my time to update it some day I'll probably post it here to redeem myself.