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Started by Drakon, September 18, 2010, 11:06:08 PM

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I managed to get my hands on this beautiful piece of electronics after a nasty bidding war on ebay

(if you don't know what this is it's a playchoice 10 dual moniter arcade board)

Then the next step was to carefully remove the rgb ppu from the socket.  I got the ppu that seems most compatible so I guess I was lucky in that respect.  It would be the mighty rp2c03b!  Since it was simply socketed I easily pried it out with a mini flat blade screwdriver.

I've have some bad experiences desoldering chips in the past.  The solder sucker I use works great but it sucked away the solder as well as the trace that the solder was connected to..........destroying the connection  :'(

So instead of desoldering I used wire cutters and clipped the pins of the original nes ppu chip since those chips are stupidly common and cheap anyway.  Then soldered all 40 wires onto the solder side of the nes pcb (solder side had soldered pins stickin out so it was just easier to solder wires to this side).  I built myself a nice little ppu mount using a small piece of breadboard and a 40 pin ic socket.  Here's what it looks like

Then I spent a crudload of time designing a rgb amp that makes the picture nice and beautiful.

It's one of these:

Then I added some resistors to make it more like this circuit:

Adding those resistors allowed me to attach the output to the moosmann amp:

then I changed some resistor strengths to get the amping strength to how I like it.  Here's the final product...

The only problem I have with this amp is it doesn't work right when running off of power from the nes pcb.  But when I hook it into my external computer atx psu it works no problem

The next issue was the stupid 72 pin slot that just doesn't connect well to games.  I noticed it has 2 slots for the connector.  One slot connects to the system pcb and it's a very regular slot.  And the other side connects to the cart and it's a piece of dung.  So I cut off the dung slot, and CAREFULLY soldered all 72 wires from the pcb onto the good slot.  This took me an entire DAY to do.

Then I stuck everything back into the case and added a port for the rgbs ground signals.  I also glued some pcb feet onto my ppu socket board and glued the feet onto the solder side of the upside down nes pcb

Then I put the case back together and built the ugliest but 100% problem/issue free cart slot.  I just removed the part of the slot with springs that lets you push it up or down and glued the slot onto the top of the case.

The scart cable is almost completely built.  I decided to make the amp external from the system so I'm gonna work on that today and update with pics.


Okay so I discovered that for some strange reason my rgb picture was getting big vertical lines on the picture EXACTLY like these ones..

obviously this kind of video interference completely defeats the purpose of installing a nice rgb ppu into the system.  I basically spent all this time between my above post and now trying to find a way to solve this issue.  Thankfully....I solved it....all thanks to user rt9342 for coming up with the idea of how to solve this.

Basically no matter how hard I searched I wasn't able to find ANY detailed info on my rgb ppu (rp2c03b, seems to be the standard playchoice ppu?).  Apparently rt9342 discovered the missing information by's what he said

"I learned about the PPU's separate grounds by accident.  When I first put a PPU socket in my NES, I left pins 14-17 disconnected, for the RGB outputs, and I figured, well, the PPU is already grounded by pin 20, so no need to ground pin 17.  And there was no picture..... until I grounded pin 17, and all of a sudden, picture!  Later, I pulled out the PPU and connected an ohm-meter across pins 17 and 20, and they were definitely not connected.  That's how I found out - I'd doubt that any info on that exists on the internet - maybe you and I can help change that."

Disconnecting pin 17 of the ppu and using it as a video ground works and clears up the jailbars but it also creates other video issues.  And if I don't leave the other ground (ppu pin 20) connected to the nes pcb the ppu doesn't work.  I later tried adding a ground wire from ppu pin 20 and using that as video ground while keeping that pin attached to the nes pcb and that finally cleared up all video issues I was having.  AND for some reason it grounds out my audio which is great because if I attach audio ground on the regular audio rca jack the picture gets worse for some reason.

Basically there's only 1 person who actually has a guide out there on how to install a rgb ppu on a nes system and that's Moosmann.

This's a pretty good guide.  The rgb amp is a bit tricky to build and didn't work at all which is why I modded the crud out of it to finally get it working..  Using a precision 40 pin ic socket I don't think makes sense.  The playchoice pcb has the ppu seated in a regular 40 pin ic socket.  Therefore I think it makes more sense to use a regular socket.  How wrong could nintendo be about their own hardware?

Keeping ppu pin 17 disconnected from the nes pcb doesn't affect anything so I just left it like that
Here's the inside of the system after I cleaned things up a little.

It's a bit overkill but makes for easy troubleshooting.  Another strange thing is my rgb amp works but the picture looks.....a bit off.  I noticed that the unamped video signal from the system is dark but has REALLY saturated colour.  So instead I just used one of my amps on the brightness wire of my s-video cable and now my picture looks absolutely perfect! (no idea why)

It's very important that you run a wire directly from the solder point on the nes pcb for ppu pin 20 and use that as video ground.  And it's also VERY important that you keep the audio ground disconnected.  On my system using ppu pin 20 for video ground also grounds out the audio and connecting audio ground from the audio rca jack makes the picture look worse.  I wound up connecting ppu pin 17 to my s-video amp ground and s-video ground and that cleaned up the picture some more.

I'm so relieved that I got this to work out.  There's nothing more annoying than installing an expensive rgb ppu into your system and getting big white lines across the screen.  My fix doesn't completely get rid of the jailbars but it cleans them up severely.


Okay I've played around a LOT with how grounds are wired and basically my nes picture now looks like an arcade machine so I'm definitely going on the right direction.  Here's some comparison screenshots of my s-video picture vs the picture of a composite signal from an unmodded nes.  The top picture is s-video from my rgb nes.  The bottom picture is composite video.  Both are taken from the same capture card.



That wiring is pure evil :-) or perhaps braided.

There is a definite improvement in sharpness but I feel that the composite images offer much more lush colours. Nice work anyway.


Quote from: Midori on November 12, 2010, 04:51:35 AM
That wiring is pure evil :-) or perhaps braided.

There is a definite improvement in sharpness but I feel that the composite images offer much more lush colours. Nice work anyway.

The wiring isn't really necessary you could just install a socket right onto the nes pcb like most people do.  I just did wires for the sake of being able to change how the ppu is wired to the nes which wound up being a huge help in cleaning up the jailbars.  The s-video has less colour because instead of amping the rgb signal I'm amping just the brightness of the s-video.  But trust me it still looks great on a tv.  Actually the composite picture has the colours too strong on my tv compared to my dvd player/pc/other stuff.  Since everything that goes into my tv now works over s-video I just turn up the colour settings on my tv and everything looks great.  Right now I'm doing a commissioned rgb nes where I'm going to amp the rgb signals themselves and once that's done (I've already installed the ppu and got it working) I'll take screenshots and trust me it will have super strong colours.  Most people who do this mod will amp the rgb signals and not the s-video like I did so don't let my screenshots make you think that this mod gives you weak colours.  And thanks for the compliment I really hope that this thread will help out anyone else who's considering doing this mod.

oh yes I also forgot to mention that the rgb ppu doesn't have exactly the same colour pallette as the composite ppu.  So in a couple of games the colours will be a tiny bit off.  But it only makes a small handful of non popular games unplayable.  From what I've read and experienced myself all popular nes games work fine with this mod and the off pallette colours don't ruin the experience at all considering the pallette is about 97% the same


I've seen a RGB NES in action actually so yeah, the colours sure aren't weak :-) Actually those colours I saw that time was almost to strong... But I didn't really care since it looked so darn nice otherwise.

It's a shame the RGB PPUs doesn't have a reliable source, having to take the from other games isn't perfect... But the only way right now.

And yeah, it's great that you document. Threads like this is pure gold for me at least :-) Keep on writing!


Project is currently on hold I'm doing a commissioned job.  Will continue once that's done  ;D

*edit* commission job still in the works but I came up with some updates since it's rgb nes related

okay so I've been rgb modding another nes and made some interesting discoveries.  Yes it had jailbars, yes I got rid of them by my patented re-wiring of the video grounds.  But here's the strange thing, after I made the amps/encoder board run off of the nes power I had to re-wire my grounds to make the jailbars go away and the picture very nice and clean.  The ppu in this system is the darker coloured one (not the white one) and the nes pcb looks a little different from the first one.  So there might not be a 100% perfect way to wire video grounds that will work on all systems and ppus.  But luckily re-wiring grounds so far has fixed all combinations of ppus and nes you just have to do some trial and error.  I've discovered that you need to connect all of your video circuit grounds either to ppu pin 17 or ppu pin 20 making sure that ppu pin 17 stays disconnected from the nes pcb.  I can tell you what I know so far....

Keeping ppu pin 17 seperate from the nes pcb doesn't at all affect how the ppu runs.  Also using this pin for ground on different parts of your video circuit really does help clean up the jailbars as long as it's kept seperate from the nes pcb.  So keeping ppu pin 17 seperate from the nes pcb is very important.

Keeping ppu pin 20 attached to the nes pcb is necessary.  Grounding parts of your video circuit to just a regular ground connection on the edge of the nes made the jailbars worse.  But grounding video amps/encoder boards to ppu pin 20 instead of another spot cleans up the jailbars.

Using the nes to power video amp/encoder boards changes the way that grounds need to be wired up.  But for anything on your video circuit like general video ground, rgb amp, amps for s-video/encoded signals, and rgb to s-video/component encoder boards you SHOULD attach the grounds of these components to either ppu pin 20 or ppu pin 17 to clean up the video jailbars.  Also keeping audio ground disconnected might help the jailbars.

I really hope this helps people who have annoying jailbars.  I've only done these fixes on systems that're being encoded to s-video and havn't tested these on a rgb screen.  Doing this won't 100% get rid of the jailbars but it gets rid of about 95% of them basically to the point where you really can't see them anymore.  Also it fixes other video issues I came across like a bright white border on the right side of graphics.  And in some cases a dark smear on the right side of graphics.

oh and ps.  Don't run the ppu off of a seperate power supply from the nes this just makes the jailbars go into full blown insanity  ;D  And also that nice super strong s-video brightness amp I built only works on my atx psu for power.  Running it off of the nes power makes it not work right for some reason.  I probably designed it wrong but it still works great on my atx psu.