Seiken Densetsu 3 / Secret of Mana 2 repro resets on menu

Hi all,

This is my first post here.

I am making a Seiken Densetsu 3 / Secret of Mana 2 reproduction cart. I have used the schematics that used to be on the now defunct French site Fudjiland. Here they are:


This shows how to connect the 74LS139.


And this shows the pinout differences between the mask ROM and the EPROMs

I have finished all the soldering. I used an NTSC Madden '97 cart as the donor (which I tested and worked correctly right before I started removing the mask ROM). The EPROMs I used are ST 27c801-100F EPROMs. When I put the cart in my SNES, the game starts and I can see the introduction scene. However, after the title screen, when I press start, I can hear the menu screen music play for a couple of seconds, but then the game resets and goes back to the Squaresoft logo. Also I noticed that during the intro, when at some point it shows the world map (and then zooms in on the Mana tree), the map's graphics are a little bit garbled, as shown in the pictures below:




I have tried several different things to try and figure out what is wrong.

The first thing I tried was to dump the modded cart. I have a SuperUFO flash cart, so I dumped the SOM2 modded cart to the SuperUFO DRAM. When playing this re-dumped version directly from the SuperUFO's DRAM, the game works correctly. This lets me think that (correct me if I'm wrong):
a. The ROM file I programmed the EPROMs with is compatible with the SNES hardware
b. The EPROMs were correctly programmed
c. The EPROMs and 74LS139 were correctly soldered to the PCB

Also, the re-dumped ROM file works correctly in bsnes.

Then I remembered that the modded cart still had Madden '97 save data in its SRAM. The game resets when loading the menu screen and this is probably when it checks for existing save data, so I thought that it was trying to read wrong data and that maybe this was what was causing it to reset. So, I started playing the game using my SuperUFO until I could save, and then transferred the save data from the SuperUFO's SRAM to the modded cart's but the problem is still occurring.

I have searched these message boards for similar issues, but I could not find any. Nevertheless, I have read this topic:
viewtopic.php?t=7445

It is about EPROM timings. I don't understand all of the technical stuff but from what I get my 100ns EPROMs should work.

Does anyone have any idea of what could be causing this? I'm a bit lost here.

Thanks.
Remslug

Seriously, when will people stop to register to nesdev to make post like this ?
It starts to get really, really annoying.

This is a nes-development board, not an super-nes-illegal-repro-selling-without-translator's-agreement board.

I posted this in the SNESdev section so I assumed I could post about SNES stuff. Although this topic is not exactly about dev stuff, I have used the search feature and found several topics about repro carts (including the one I referenced in my previous post and others like this one: viewtopic.php?f=12&t=8289). Otherwise I would not have started this topic here. The information in these posts was interesting and people obviously knew what they were talking about so I thought I could get some help.

Now about your "super-nes-illegal-repro-selling-without-translator's-agreement" assumptions. As far as I'm concerned, I'm not doing anything illegal. I do not sell repros nor will I ever. I could play this game using my SuperUFO, but I want to make this cart as a hobby/pastime. I have a legally acquired original Japanese copy of this game and the translation is available for free use on Neil Corlett's web site. The patch's readme file even mentions this (which means the translator is not against people using his translation in an EPROM cart):


I'm sorry if its not the correct place to ask about repros, but please don't assume people are doing illegal stuff before even asking.