Famicom PPU+CPU to NES(PAL) mod

[jpx72]

This is a little proof of NES-Famicom similarity:

These are pictures of my modded -PAL- NES: the PPU, CPU and the CIC chip were removed, and I've placed chip sockets instead of them. The CIC chip has the region lockout disabled by adding a switch on one of it's legs, that's a classic mod for removing the lockout, nothing special.

But instead of the original PAL chips (CPU and PPU) I've reinserted PPU and CPU from a broken Famicom (which has NTSC standard). I had to exchange also the Xtal, cause the Famicom's -NTSC- PPU needs different frequency to run at.
So there it is, a working NTSC NES with Famicom's "brain" inside. Working like a charm.
(yes, now it's a normal NTSC NES, like all other NESes in US, but in Europe )

And by the way, the screen is perfect, no vertical/horizontal bars, no interference, just pure NES-awesomeness (of course now it's detected as NTSC by my TV)

[MWK]

Nice work jpx72.

Have you tired to socket down a CPU+PPU from some PAL famiclone before swapping the crystals ?

[jpx72]

An interesting thought, no I haven't tried it, but in another project I did, I have exchanged Famicom's PPU with famiclone(PAL) and it didn't work untill I've exchanged the Xtal. So I'm thinking there might exist a famiclone with some custom PPU that works in both PAL and NTSC, but I haven't seen one yet.
What about that custom HongKong Famicom? Does this one have a multi fruequency PPU or it's only NTSC and the custom chip only slows it down in PAL mode?

[Xious]

The HKFC has an NTSC CPU/PPU, as I suspect your clone does as well. The PAL output is derived from some interesting electronic trickery on the RF/Power board. (NCL even patented this concept, which may have expired by now, but I'm not certain as I don't know when they filed it.)

You may want to examine how they did that. I'm curious about the SECAM NES from France with RGB adaptation built-in (but not raw RGB, for you folks getting your hopes up).

Those systems may make awesome candidates for NEScades.

An interesting thought, no I haven't tried it, but in another project I did, I have exchanged Famicom's PPU with famiclone(PAL) and it didn't work untill I've exchanged the Xtal. So I'm thinking there might exist a famiclone with some custom PPU that works in both PAL and NTSC, but I haven't seen one yet.
What about that custom HongKong Famicom? Does this one have a multi fruequency PPU or it's only NTSC and the custom chip only slows it down in PAL mode?

[jpx72]

I have read that the French NES has only a Fake scart cable - that is, there is a scart cable but the only connected pin is that of composite output. So not a chance of getting RGB. But I may have heard wrong...

[Xious]

It's SCART, yes; however the SCART connection provides separated R/G/B composite video signals, which is interesting for some uses. It won't be any better than A/V in the end, but it allows the use of certain viewing devices, and it would be a curiosity to replicate the connection for non-PAL systems, if that is even possible, in order to hook them up to other types of monitors.

See: http://blog.hardcoregaming101.net/2009/12/french-nes-with-rgb-output.html

I'm not entirely sure what would happen when mixing the PPU from the French system with an NTSC CPU and X'tal. It'd probably go nuts, but it couldn't hurt to play with it. I'm hoping that as long as the monitor supports SECAM/SCART R/G/B inputs, it may work.

[jpx72]

Thanks xious for the link, I was searching for a info page about that French beast for a long time! It's interresting, I think I must look for one myself.
From what I've seen there, I think the PPU is the same as any PAL, only the extra chip hidden in the RF box is responsible for the RGB magic. But can't be sure...

[Xious]

That's my guess too. I'm wondering how that RF + SCART set-up would like NTSC inputs. Don't forget to get a suystem with a SCART cable: I'm pretty sure Nintendo's cable is non-standard, specific to the port o that one system.

[133MHz]

Well written article and nice pictures, but seems to be obfuscating the point about the French NES being a plain PAL NES with a PAL-to-RGB transcoder inside the RF box, not mentioning it explicitly but leaving it "buried" into that 2005 ASSEMblergames forum thread.

The RGB connector on the back of that NES seems to be the same one used in the FDS RAM adapter, which is little different than the SNES/N64/GC Multi AV port. The pinouts may even be (mostly) the same, being only a mechanical incompatibility.

As for what would happen if you were to apply NTSC NES video to that RGB transcoder box, my bet is that you'd get a steady 60Hz B&W picture or a rolling 50Hz B&W picture, much like displaying NTSC video on a PAL only TV. It might be modifiable by changing the logic state of a NTSC mode pin or similar and replacing the color crystal. I don't see that transcoder being too "smart" given its purpose and manufacturing period.

Thanks to a YouTube video about the French NES I learned that you can get PAL composite out if you can tell your TV to ignore the RGB signaling (force composite using the menu on the TV or disable pin 16 signal). That could be a good point for comparison between the two.


My Ultimate Dream NES™ that I'll probably never realize would be something like this:

• Get a French NES with SCART lead


• Get a RP2C03 RGB PPU


• NTSC-ize the French NES by replacing CPU & crystal like jpx72 did (or just swap the entire motherboard but that's amazingly harder)


• Remove PAL-to-RGB transcoder chip from the RF box and reuse its output amplifiers (if any)


• RGB mod the NES using the '03 PPU


• Hook up the RGB lines from the new PPU to the output amplifiers on the RF box (or build RGB amp and hook up directly to the RGB out port if the former is not possible)


• Enjoy completely stock true RGB NES!

[jpx72]

A DreamNes(tm)! That would be great...
Meanwhile somebody really should persuade some chinese manufacturer to build a pile of NTSC RGB PPUs (the playchoice ones)... Even I would have a job this way, offering my desoldering (machine) skills! (and xious would be building RGBamp modkits )

[io]

Hi,

Thanks to a YouTube video about the French NES I learned that you can get PAL composite out if you can tell your TV to ignore the RGB signaling (force composite using the menu on the TV or disable pin 16 signal). That could be a good point for comparison between the two.

That's weird, because I recently mod one of my french RGB NES to output composite.
And before doing that I did test if composite signal was available from the A/V connector (pin 1) and the SCART (pin 20) and it wasn't, it seems to be only a synch signal for RGB.

French RGB A/V cable pinout :
Original in french and  Google translated in english (numbers are a bit messed up after "translation")
Old pics I took of the SCART side.

My modded RGB to composite NES :
Original in french and  Google translated in english

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

By the way, your modification is very interesting jpx72. I will try it with a spare Famicom (with an horrible shell) lying in my attic.

Hummm... and I could solder the french PPU, CPU and Xtal on the Famicom board and make a portable (after replacing the cartridge connector too) because Famicom boards are smaller.

[jpx72]

Related topic:
http://www.famicomworld.com/forum/index.php?topic=6749.0
Post Merge: November 21, 2011, 10:47:42 pm

Hummm... and I could solder the french PPU, CPU and Xtal on the Famicom board and make a portable (after replacing the cartridge connector too) because Famicom boards are smaller.

Well you won't get anything better with French PPU, CPU and Xtal than with any other European PPU CPU and Xtal. The difference is the chip that lies in the RF box - the one responsible to decode composite signal to RGB.

[io]

Yes, I know that all the difference is in the daugther board (I have 3 different kind of NES : US, european and french).
My aim is not to get something better with the "french" PPU/CPU/Xtal (I wrote french just to note from where them came from). It's just that if I remove them from a working french RGB NES motherboard, instead of throwing them in the dustbin, I can re-use them in the sacrified Famicom motherboard.

Then I mod this mutant Famicom to output composite and I get a working console... I don't like to toss out stuff

And thank you for the link.

[jpx72]

...yes, but you can sell the FRA board to me and buy PPU and CPU (and xtal) from 80sFREAK. This will be better for you, because 80sFREAK is selling NTSC chips, and when you put chips from your French board, you will have a PAL Famicom.
But if you really want PAL Famicom, I will exchange my PAL PPU and CPU for your FRA board. ... what do you say?

[io]

But if you really want PAL Famicom, I will exchange my PAL PPU and CPU for your FRA board. ... what do you say?

I have a PAL NES and a Famicom, and I want to invert their PPU/CPU/Xtal to get a NTSC NES and a PAL Famicom...
so I say it's easier for me to do it with what I already have :p

...yes, but you can sell the FRA board to me and buy PPU and CPU (and xtal) from 80sFREAK. This will be better for you, because 80sFREAK is selling NTSC chips, and when you put chips from your French board, you will have a PAL Famicom.

If I sell you my board, I won't be able to mod this board to get an NTSC one

By the way, if we think about it, what you need is a RGB daughter board, not the whole board.
This I may can provide when I do my next NES mod, but it will be without the power and A/V connector.