Hello,

I need a little help with a reproduction cart I made of Devil World.  I've made repros of FFIII and Simon's Quest Redacted and really didn't expect to have trouble with a simple NROM chip swap for Devil World, but here I am.

I used Golf as a donor so the mirroring should be fine, they are both listed as horizontal mirroring.  
I used 27C64 for CHR ROM and 27C128 for PRG.  I bent up the VPP and PGM pins on both chips.
Then I dropped them into position, soldered it together and went to play it.

The game loads fine and plays perfectly for about 3 minutes.  After that glitches start to form.  The graphics get progressively worse until the entire screen is a mangled mess.  The rest of the game seems fine.  
I thought it might be dirty connectors but it's not.  

Anyone have any ideas about how to fix this?

Thanks

I'm gonna guess its a bad eprom, try burning another one at a slow speed. Or maybe one of the pin holes is damaged, it happened to me and made the game graphics garbled. Either way it sounds like the rom isnt working as intended. Of course, other people here know a lot more tham me and I could be wrong.

Did you ground/+5 all pins?

You don't need to bend up pins for a NROM or CNROM reproduction. Just program, drop in, and solder.

Sounds like a short around the CHR rom. Did you clean the board after removing the chips? Sometimes dust and particulates end up getting trapped under the chip and cause a short circuit.

That's all I can think of as it sounds like you did the rest right.

Thanks for the advice.

Yes, the ground pin and VCC are in the right holes. I'm going to check the board for bad connections tonight. This is actually the second time I've attempted Devil World. The first time I got no response at all from the game, just a blue screen. I think it was a bad split of .nes file. I checked the files, and burned again. I did two sets of roms the second time and made two copies of the game. I know I don't need to bend up Vpp and PGM, but these aren't used anyway so I figured it couldn't hurt. Both copies have the same issue. However, one of them will play about twice as long as the other before glitching up. It seems unlikely that I would have a bad solder point on both boards, but I think it's either that or bad eproms.

I'll let you know if it turns out it was just a bad connection.

So, I cleaned off the board and tried it again... still glitchy.

I have ordered some new 27C64 dips and will attempt this again when they arrive.