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PostPosted: Fri May 15, 2015 6:00 pm 
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Hi, I'm a super noob to the forums, but I've been lurking for a while.

I am an electrical engineering student and avid retro gamer. I am interested in converting famicom carts to english using either official NES rom translations or fan translations. Specifically, I have a copy of Princess Tomato in the Salad Kingdom that I'd like to flash to the US rom version. The reason for this is both as a learning experience, and also I have an A/V Famicom as my primary Nintendo, so the carts look better in there. I have access to an *prom flasher, so really my only barrier to entry is knowledge.

I'm looking at the mask rom pinout here: http://wiki.nesdev.com/w/index.php/Mask_ROM_pinout

My question is on which legs will I need to lift on a 27C64 eprom in order to place in the mask rom socket? If I'm understanding the article, I will need to lift A16 - 19 and bridge them to the place under the PRG column. So for example, I would lift A19 and wire that to the PCB where A17 would normally go. Is that correct?

Also, will I place the eprom so that the lower pins match up? I think pictures would best describe what I'm talking about here.

Picture A:

Image


Picture B:

Image



Also, as a confirmation, which eprom size will I want for this rom?

I think that's all my questions for now, but if there's something obvious I'm missing here please let me know! Thanks in advance for any help you can give me!


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PostPosted: Fri May 15, 2015 6:14 pm 
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Location: Seattle
catskull wrote:
27C64
Danger, Will Robinson! That is a 64 kibibit UVEPROM, suitable only for NROM CHR and/or Galaxian's PRG.


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PostPosted: Fri May 15, 2015 6:45 pm 
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lidnariq wrote:
catskull wrote:
27C64
Danger, Will Robinson! That is a 64 kibibit UVEPROM, suitable only for NROM CHR and/or Galaxian's PRG.


Oh snap! Thanks for that. Bootgod says is 256KB, is that kilobit or kilobyte?


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PostPosted: Fri May 15, 2015 7:11 pm 
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Location: NE Indiana, USA (NTSC)
NesCartDB sizes are in kilobytes.

If you want to see whether a particular database uses bytes or bits, look up a game with a known size. For example, Super Mario Bros. has a 256 Kbit PRG ROM and a 64 Kbit CHR ROM, and its iNES image is 40,976 bytes (16 bytes header, 32,768 bytes PRG ROM, 8192 bytes CHR ROM). A reproduction would use a 27C256 or bigger for PRG ROM and a 27C64 or bigger for CHR ROM. NesCartDB's entry for SMB1 reports "Mask ROM 32 KB" and "Mask ROM 8 KB", so NesCartDB must be using bytes.

With two 27C64s, you could probably make Forehead Block Guy, which uses only the first 6.5 KiB of its PRG ROM. Cut out PRG ROM $1FF0-$3FEF after splitting, which is blank in FHBG, and it should work.


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PostPosted: Sat May 16, 2015 9:23 am 
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Thanks for all the input. Can someone confirm that the eprom I need is the 27C020?

Also can someone confirm about lifting the legs and bridging the wires?


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PostPosted: Sat May 16, 2015 11:47 am 
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Yep the 27C020 are 256KB chips, and should work fine.

There is a guide on how to do the wiring, by Callan Brown here. That guide is for MMC3 games, but the wiring is the same for PRG.

Also, in your pics the EPROM is facing the wrong way! Flip that around, the indent should be facing the outside of the cart (same as the PRG maskrom thats on there already).


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PostPosted: Sat May 16, 2015 12:23 pm 
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getafixx wrote:
Yep the 27C020 are 256KB chips, and should work fine.

There is a guide on how to do the wiring, by Callan Brown here. That guide is for MMC3 games, but the wiring is the same for PRG.

Also, in your pics the EPROM is facing the wrong way! Flip that around, the indent should be facing the outside of the cart (same as the PRG maskrom thats on there already).


Thanks for that confirmation. Going forward, am I safe to just stock up on 512KB chips? I can just double/quadruple the rom if needs be, right?

About the picture, is my face red! :oops: I didn't intend to place the chip in the picture, thanks for pointing that out!


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PostPosted: Sat May 16, 2015 3:22 pm 
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Location: Germany
512kb (27c040/27c4001) are just fine for nearly any reproduction out there.
However, NROM boards use 28 pins so you will need 27c512 for them.

UNROM/UOROM uses 28 pin as well but can be changed to support 32 pins.


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PostPosted: Wed May 20, 2015 7:21 pm 
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Thanks to everyone who helped out! I finally got the correct eproms and everything went super smooth! Can't wait to do more conversions. Looking at you Lagrange Point!

Image

Image


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PostPosted: Fri May 22, 2015 2:53 am 
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You broke the cart tabs while opening ! :shock:


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PostPosted: Sat May 23, 2015 8:25 pm 
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aarkay_14 wrote:
You broke the cart tabs while opening ! :shock:


I know, I'm sorry. I didn't really know what I was doing at the time (well I guess I still dont). That's why I wanted to try on a cheaper game first.

I do have another question though. Tonight I tried my hand at Lagrange Point using the larger 27C40 eprom. I followed the exact same steps for the PRG ROM but once I soldered everything up I get nothing. Does anyone have any tips for me? Is there a reason why Lagrange Point would need different pin swaps than Princess Tomato?

Here's the board:

Image


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PostPosted: Sat May 23, 2015 9:02 pm 
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Location: NE Indiana, USA (NTSC)
Non-Nintendo Famicom boards are more likely to already to use the EPROM pinout.


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PostPosted: Sat May 23, 2015 9:53 pm 
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tepples wrote:
Non-Nintendo Famicom boards are more likely to already to use the EPROM pinout.


Hmmm, I just put it in without lifting any legs and I still just get a white screen.


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PostPosted: Fri Jun 05, 2015 10:02 pm 
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Just an update here: I was able to get this working. I got a new eprom and soldered it pin for pin in place of the mask rom and it worked first try!
Notes:
The exact eprom I used was a 27C4001 from ST.

Lagrange Point will show a grey screen for approx. 1 second before showing the title screen. Make sure you're leaving it on long enough and don't just assume you have a bad flash right away!

I was able to replace the battery with a socket using this part: http://www.ebay.com/itm/5-x-New-Button- ... 2c61fdce98
I had to bend the legs of the socket a bit and I used a clamp to hold it in place while soldering but it seems to fit fine and it fits inside the cart shell with no problems.

The first time I started a new game with the translation, the name at the new game screen was a bunch of jibberish. This seems to be because the game stores whatever the last name entered was in memory, so it was probably filled with garbage data from the japanese tileset. Once you overwrite the name with a good one, you won't have that problem. Also if you remove the battery and don't start a Japanese game before you start the English one, you shouldn't have that problem.

More info will be on my blog: catskull.net

Thanks to everyone for their help!


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PostPosted: Wed Jun 10, 2015 8:13 pm 
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Location: Brasilia, Brazil
The Lagrange Point translation has a bug:

When you boot the game with a blank save memory it will glitch the name entry screen. That happens only on the very first power cycle if the memory is blank. Next time you use that screen it will work correctly.

Considering they made the miracle of fitting the translation on the original ROM space I don't think it's fair even consider that being a big problem.


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