Replace famiclone brains

Hi!

I have a nice old famiclone:

It's been mine all its life, since I was little and I like it so much. However, due to recent research, I learned it has the problem of reversed duty cycle so the music in the games doesn't sound 100% accurate. So, I obtained an NES board, took its CPU/PPU and put them in the famiclone (got the idea from here: http://133fsb.wordpress.com/2009/11/28/ ... ne-part-2/). It was easy because the famiclone doesn't have its CPU/PPU soldered to the board, instead it uses some nice sockets for the chips. Here's a picture of the famiclone board (with its original chips):

Now the problem: the famiclone won't work with the NES chips. Doing some tests I noticed these combinations work/fail:

original famiclone CPU + original famiclone PPU = it works
original famiclone CPU + NES PPU = it works
NES CPU + original famiclone PPU = it doesn't work
NES CPU + NES PPU = it doesn't work

so this seems to mean the NES CPU is not working. When I say "not working", it means that when turned on the famiclone will show a purple screen and nothing else. Resetting it has no effect at all, not even a blink on the screen.

My questions are:
- Is there a way to test if the CPU is effectively dead, or if it's maybe some incompatibility with my famiclone? I have a voltmeter and know how to use it, but not much else (no oscilloscope for instance).
- If the CPU is dead: can somebody please sell me a working NES CPU? I will gladly pay for it. Please keep in mind that I'm in Latin America.

Thanks!!

There's no requirement that a famiclone's CPU/PPU be pin-compatible with the ones in an NES. The circuit design could be very different.

Hi!

You are right, rainwarrior. However, from what I have read, the old famiclones (this one is from the early 90's) are usually chip-by-chip copies of the original family computer (even the chips layout looks almost identical to the original family computer), so that (and the link I posted earlier) got me thinking into the possibility of using the NES CPU/PPU to power it. Also, the PPU seems to be compatible, so I guess there is a chance that the CPU is also compatible. That's why I need to know if the CPU I have is fine (which means my famiclone is not compatible with it) or is damaged (which tells me nothing about the famiclone compatibility).

Thanks!

Do you have any advanced testing tools? (oscilloscope, logic probe, &c). Try my checklist: viewtopic.php?t=9555

Hi!

Sorry, no. I do not have or know how to use anything more advanced than a voltmeter. So, back to the original second question: could anybody here please sell me a known-good American NES CPU?

Thanks!

Actually, a voltmeter may be helpful here. With that you can at least test that the power, 5V, is where it is supposed to be.

^Or use the voltmeter's continuity setting to test if traces are going to/from the same places on each board.

Thanks for the suggestion. I got this pinout for the NES CPU: http://wiki.nesdev.com/w/index.php/CPU_ ... escription so, from what I can understand, the famiclone board should give 5V between pins 40 (+5V) and 20 (Ground). is that right?

Unfortunately, the NES board got badly damaged while extracting its CPU and PPU, a hot air gun was used and some of the tracks got damaged so I don't think this test would give correct results.

Thanks!

If the board was damaged how are you so sure that the CPU or PPU was not over exposed to heat and damaged too?

That's exactly my point here, I am not sure. I know the PPU is fine (See 1st post) but no idea about the CPU, that's why I need to test it somehow, but it seems that needs more tools that I have available, so I would like to know if anybody can please sell me a known-working American NES CPU.

Thanks!

There's plenty of them on ebay, I wouldn't guess you'll find someone here with good spares sitting around they'd be interested in selling. A heat gun isn't the best means of desoldering through hole components especially DIP-40's. I'd suggest trying again and invest in a desoldering tool from radioshack and do it right this time Then if you don't damage the PCB you could put a socket in the NES mobo. And swap back and forth on that to ENSURE you've got a good CPU. If the board you just heat gunned to death was still repairable I'd just suggest putting a socket in there to test your CPUs and make sure they're pin compatible.

As an aside, if you love this famiclone so much haven't you learned to love the wrong duty cycle by now? If you want authenticity why not just go for an original NES/FC? Just seems a little backwards to me sacrificing an original console (or two) to make a clone more accurate...

I learned to love it in the games I have from my childhood (Super C, Double Dragon II and III, Robocop II, TMNT II...), but recently got some more games for it that I didn't have when I was a child (Castlevania III for instance) and it sounds badly compared to the original sound. The reason I prefer destorying an NES board to fix the famiclone over having an original NES is actually four reasons:
1. The famiclone is what I grew up with, an NES means nothing to me (it doesn't have that sentimental value) even if the games look/are the same.
2. It's cheaper to find a broken NES board and get the chip than buying a complete NES (which I would have to buy in the US and import it, since Nintendo never sold NES in Latin America. The NES is a really rare thing where I live.)
3. The 60-pin connector in the famiclone seems more robust than the 72-pin ZIF from the NES, besides I have the converter to use NES games in the famiclone.
4. The famiclone can use the extra audio sound chips in the japanese games (Akumajou Densetsu for instance), whereas the NES doesn't unless you modify it (which requires skills a bit over me).

The desoldering process wasn't done by me (as I've told, I don't have those skills). It was done by a "professional" who obviously is not as skilled as I thought.

Therefore, that's why I'm looking for an original CPU for my famiclone

Thanks!

Desoldering isn't that unreasonable of a skill to learn on your own when done with the proper tools. If this is something you want this badly your best bet is honestly to not avoid your most reasonable options because "you lack skills". If nothing else since you're ditching the whole mobo you could test your desoldering skills on other smaller chips. Although that leaves fewer debug options/tools.

One reason I'm saying you're unlikely to find someone here who has a CPU to sell is because most of us aren't interested in sacrificing an entire working NES for it's CPU alone. Honestly I have one I could sell you if I really wanted to, but this isn't a worth 'use' for the one spare CPU/mobo I have unless you were offering an unreasonable amount.

I'm not trying to be a jerk, just trying to motivate you to take on your project including acquiring any needed skills. It's obvious your passionate about getting this thing to work, so it seems reasonable that you'd be willing to learn a simple task to accomplish your goal. Most of us enjoy helping out with suggestions and giving advice, not doing all the work to solve your problems

You can properly desolder a CPU or PPU or whatever dip chip with nothing more than a 15 watt soldering iron and a suction type solder pump pen. You won't damage the part if you don't do anything really dumb.

I have a NES console that appears to have a dead CPU and a live PPU. If I have spare chips I'd consider trying to sort that out, but since you can't really just get loose CPUs and PPUs there just isn't anything that can be done. Shouldn't the US and Japan consoles have the same CPU and PPU chips? You could possible source a good CPU from a messed up Famicom maybe.

Good luck finding just a CPU. Maybe you can find a broken NES on eBay and the CPU will be OK if lucky.

Maybe an alternative is to get a working famicom and just swap the whole board into the familiar famiclone casing.

Thanks a lot for your suggetsions!! I think I will try to get a good (de)soldering iron and try to learn what I need to get this done, as infiniteneslives suggested. I am not sure about the CPU in the family computer, teoretically it should be the same as the NES one (both being NTSC) but I am not 100% sure. Anyway, finding a famicom here is even harder than getting an NES, and importing from Japan is even more expensive than importing from the US, so I guess the NES is still the best option. I'll see what I can do to get the components and try to do the desoldering myself, based on your suggestions.

Thanks again