Trying to RE and fix an old Atari 2600 cartridge

Discussion of development of software for any "obsolete" computer or video game system. See the WSdev wiki and ObscureDev wiki for more information on certain platforms.
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Fisher
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Trying to RE and fix an old Atari 2600 cartridge

Post by Fisher »

Hi.
Recently I got an Atari 2600 game that wasn't working.
Unfortunately, I didn't have enough time to properly disassembly and photograph the PCB, but here's what I've got:
Component side
Component side
The game is Smurfs - Rescue in Gargamel's Castle.
After I connected the D3 and D4 from the left ROM on D3 and D4 to the right ROM the game boots but crashes when I jump.

So far so good, I tried to get its schematics with a multimeter, which I think would be the best way to try to troubleshoot it.
Since the ICs have their ID erased, I tried to guess who is who, but I'm still in doubt about one of them.
I'm not sure if the IC on the top left of the picture is a 74'01 or a 74'02, maybe I'm wrong and it's none of them.
Can someone please tell me which of these schematics makes more sense, if they even do some kind of sense?

Thanks in advance.
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Joe
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Re: Trying to RE and fix an old Atari 2600 cartridge

Post by Joe »

It's a 74'02, which makes it a two-ROM version of the F8 mapper. Accessing $1FF8 enables one ROM and accessing $1FF9 enables the other.
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Fisher
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Re: Trying to RE and fix an old Atari 2600 cartridge

Post by Fisher »

Thanks!
It's nice to know that I'm starting to learn how to do this stuff. :-)

I marked all the ICs with my cheap Dremel knock-off, except the IC I had doubts about it
WhatsApp Image 2022-09-10 at 13.02.16.jpeg
I tried the IC on my tester with either the 70'01 or 74'02 configuration and it said it was defective.
In fact the only IC it says that's fine is the 74'74!
I think I need a better IC tester...

By the way, what would be of a RE thread without some nice PCB p0rn!?
Here it is. The scans of the naked board, or what was left of it after I removed the ICs:
Componentes - peq.jpg
Solda- peq.jpg
I dumped and tested the ROMs and according so Stella, the CRC after emerging the files is fine.
So the only thing left that could be causing the bug would be bad or broken contacts/tracks.
So I'll try to redo the tracks, clean the contacts an reassemble to see what I will get.

Again, thanks in advance.
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