Issues with translated EPROM in Lagrange Point cart.

[cr4zymanz0r]

So, a handful of months back the fan translation for Lagrange Point on Famicom was completed, but due to the special chip/mapper in the cart it is not currently compatible with any NES/Famicom flashcarts.

I've seen some people taking the "repro" approach of taking the original cart and replacing the original ROM chip with an EPROM that has the translated rom file programmed on it so it can be played on original hardware.

I'll start with the issue the give details on my research/troubleshooting to see if anybody has ideas.


Issue: When the EPROM is installed in the cart, the system just boots to a solid color screen (the same as if no cart is inserted).

Troubleshooting: Desoldered the ERPOM after things weren't working, installed a precision socket, put the original ROM chip back in and the game works fine. Removed the original ROM chip, inserted EPROM, still just a solid color screen. I even tried it on two different systems (AV Famicom and my toaster NES that I modded to have a Famicom cart slot too).
I don't have any equipment to program EPROMs myself, so I had an online friend that's been doing repros for a while program the EPROM and mail it to me. He used a prepared and translated rom file provided by another repro-er who has done a Lagrange Point cart. My online friend also verified it works in an emulator and was ready to be written to an EPROM (header removed, whatever else is needed). He also verified the write to the EPROM was successful. Unfortunately, he did not have a Lagrange Point cart for him to foolproof test it. I also triple checked that I wasn't inserting the EPROM backwards.

Research: Lagrange Point uses one ROM chip (where a lot of NES/Famicom games use 2 with one being for CHR and another for PRG). The ROM chip used is 512kbyte/4Mbit. According to what I've found people saying, a 27C040 EPROM is the same size and is a pin for pin replacement.
Direct sources:
http://krikzz.com/forum/index.php?topic ... 2#msg23652
http://krikzz.com/forum/index.php?topic ... 7#msg23907

At this point I'm pretty baffled as to what the issue is. I'm doubting my online friend botched writing the correct file/data to the EPROM since he's a very technical person and has done hundreds of repros, but at the same time the only issue I have is when I insert the EPROM into the cart. Is there possibly contradicting evidence that a 27C040 EPROM is not pin for pin compatible as stated in the external forum posts? Any suggestions are welcome.

[ApolloBoy]

Is there possibly contradicting evidence that a 27C040 EPROM is not pin for pin compatible as stated in the external forum posts?

I don't think so, I used a 27C040 for my LP translation and the game works just fine. I'd make sure the EPROM in question was thoroughly erased beforehand.

[andy251203]

I can second this. I used a 27c040 in mine and it also worked fine. 99% sure your problem is that your eprom was not programmed correctly. Invest $50 in a Willem programmer and do it yourself.

[muckyfingers]

Lagrange Point use a 27C4001 or 27C040 (same chip, different part number) as a direct pin for pin replacement. If your socket is working with the original rom then it means the chip you have is either bad, or programmed with an incorrect/corrupted file. If you need the chip reprogrammed let me know, just pay shipping both ways. I made myself a Lagrange Point translated cart, and have the equipment to test your EPROM. I'm located in SoCal if by chance you are nearby.

[muddy]

Hello all,

A friend of mine is writing the eprom for me, and is asking what speed the 27C040 needs to be?

Pics of the LP on krikkz forum looks like it's a 27C040-15. Can anyone let me know what speed chip they used?

thanks!!

[Einzelherz]

Does it only require a change of the PRG?

Edit: didn't see that it only has one chip.