nesdev.com

Hi there, I struggle with a problem I can't solve by now. I have a Famicom Classic console (the first version, not classic mini) that functions rather strange- all normal carts work just fine and the games work just as normal and you can play through them but all multicarts I have simply refuse to work. They freeze right on the selection menu or while the game starts. There is no exception, ALL multicarts I have just don't work at all

What I've done is change 74LS139 into a new one, replaced the voltage regulator for a new one and added a small capacitor to the PCB from another Famicom (originally I noticed some empty slot for a small cap so I added it) but there is absolutely no change whatsoever, the console behaves the same. I think there is some problem with M2 pin or clock in the console but can anyone guess what may be faulty here the most likely?? Maybe some small component should be replaced or changed or something??
http://nesdev.com/Ntd_8bit.jpg

Please for help and suggestions, many thanks in advance!!

The Control Deck is model HVC-001, correct?

Do you have an adapter to try 72-pin cartridges like Super Mario Bros./Duck Hunt and Donkey Kong Classics?

Yes the model is HVC-001. I don't even have Mario Duck Hunt carts or any NES carts lol

Try bigger capacitor for the one that holds console in reset after powerup.

OK bigger but what value?? The original cap is 0.47uF if that's the correct cap I'm looking for but I don't think it's the issue here. I just soldered 2x 0.47uF = 0.94uF in place and still no luck, the same things happen...

Multi carts sometimes rely on the CIC (RESET Signal) from what I noticed. If using a NES anyway. But that's not the case.

Also check if CHR ROM /OE is connected to cartridge connector pin 17. If it isn't lift it from the board and connect it there.

Got any pictures of the carts PCB (front/back)?

WTF its not the case here... Those multicarts are made in 1990s and they are 100% fine

On the side note, I heard that there are some Famicom motherboard revisions with minor changes, my Famicom is HVC-CPU-05 that causes problems with multicarts. Anyone have any idea how to fix it if possible??

Someone else had a problem with multicarts on HVC-CPU-05 revision. The earliest boards, especially from the square button era, may have different electrical characteristics that cause M2-interruption reset detectors to perform less reliably.

Wow this looks like my problem actually. Do you have any solution for this?? I couldn't spot any definitive answer in those topics

OK, it looks like I've found solution to my own problem (probably)- it looks like the CPU is probably defective. I have no idea whether these older CPUs are worse or my unit was just broken. I did a test where I swapped CPUs between this faulty Famicom Classic and working Famicom AV. Once I tested Famicom AV with the iffy CPU, multicarts didn't work and normal games worked even worse, overall the console behaves strangely but when I tested Famicom Classic with Famicom AV CPU, the console worked perfectly fine, even with all multicarts. So to everyone that has a Famicom Classic with the motherboard HVC-CPU-05 I suggest you should test if your board can play multicarts or flashcarts like Everdrive. Looks like the worst possible scenario unfortunately but at least I've found the issue, the only thing I can do here is swap the processor from another donor I think

The 2A03 is significantly different from the later 2A03E and 2A03G CPUs in ways that are known to be incompatible. For example, Vs. System mainboards won't work at all if given a newer CPU.

I wouldn't assume that your 2A03letterless is defective at all.

The part number is RP2A03, so yes it is letterless. Does it mean that the CPU is probably "100% working" but it is incompatible?? If I can't play any multicarts then the CPU might as well just be defective for me...

Yeah, I'd say it's exactly that. "100% working but incompatible"

I suspect someone else would happily trade a functioning later-revision famicom for your older less-compatible famicom.

If you or anyone else is interested in buying or trading this unit then you are free to go. The console was meant to be given away and it has been AV modded, as well as reduced jailbars