Alternate type of power supply for Famicom

[toadhall]

I've been studying this Famicom schematic just to familiarise myself with the mainboard and to help make future mods easier for myself.

If I were to remove the RF/Power board (after an AV mod let's say), would it be possible to wire in a 5V USB power supply directly into P3? It would have to be from a regulated, dedicated USB power supply of course and I was thinking a good one that provides 1000mA should be enough, like an iPhone charger. I doubt a PC USB port would be enough, though perhaps a Y double connection might help. The Famicom needs at least 850A and PC USB ports tend to provide 500A at best. So a dedicated, proper USB power supply would be the way to go.

What do you guys reckon? Am thinking of doing this as a rainy day project one day for one of my spare Famicoms.

Bonus question: There seems to be a lot of potential power inputs on the mainboard! Am I right in thinking I can provide power via inputs such as the controller ports and even the cartridge port(!)? If so, that would be CRAZZZZYYYYY  

Thanks in advance for any feedback!

[Pikkon]

I have ran a snes off 5v just plugged into my pc so yes it should work.

So do you just want to wire up a usb?

Since the famicom has a 7805 you will want to start there,if you wanted to do it real quick solder the postive usb wire to the input and the output of the 7805,and ground is the middle and the power switch will not work as you would have to wire that up as well

[toadhall]

I have ran a snes off 5v just plugged into my pc so yes it should work.

So do you just want to wire up a usb?

Since the famicom has a 7805 you will want to start there,if you wanted to do it real quick solder the postive usb wire to the input and the output of the 7805,and ground is the middle and the power switch will not work as you would have to wire that up as well

Wow, a SNES! You didn't have problems with not providing enough current?

If I were to solder to the input and output of the 7805 wouldn't I have to take the regulator out as well? In any case, I was curious if I could bypass the whole RF board and power it up without it.

[Great Hierophant]

Most USB wall-warts can provide 1A and the SNES only requires .85A.

[toadhall]

Well yes, but Pikkon said that he plugged it into his PC which don't normally provide 1A through USB.

[famifan]

well, technically you probably might power up your famicom via the different VCC/GND points.

BUT

you have to consider the PCB traces resistance and overall power consumption. In other words, just think of it as the PCB was designed to be powered via only certain points. Other points could be weaker.

OK, since the famicom doesn't drain too much current, it will most certainly operate with no flaws.

Also, please bear in mind that the analogous part of famicom could be very picky about VCC/GND points and could start to produce extra amount of noise/humming.

[P]

What about power spikes? Doesn't the 7805 give extra protection aggainst such unwanted things?

[Pikkon]

You could add a fuse and a nice power cap to give it protection.

[toadhall]

well, technically you probably might power up your famicom via the different VCC/GND points.

BUT

you have to consider the PCB traces resistance and overall power consumption. In other words, just think of it as the PCB was designed to be powered via only certain points. Other points could be weaker.

OK, since the famicom doesn't drain too much current, it will most certainly operate with no flaws.

Also, please bear in mind that the analogous part of famicom could be very picky about VCC/GND points and could start to produce extra amount of noise/humming.

Cool! So you can theoretically do it, it's just not a good idea. I guess it could come in handy when trying to diagnose a power issue or faulty 7805. Maybe I could wire a usb cable to expansion port or something and temporarily power it from there to diagnose a mainboard?

What about power spikes? Doesn't the 7805 give extra protection aggainst such unwanted things?

You could add a fuse and a nice power cap to give it protection.

Plus, make sure to use a good regulated power supply as well. Should be ok.

[Arkanix38]

Any source of regulated 5V power with enough current capability should be fine to run a Famicom. From the 7805 output/ground pins any regulated 5V supply will be treated identically as long as it can provide enough juice to run whatever you're doing. Some PCs have USB charging ports which can provide more than 500mA and these (with a little circuit protection) should be ideal.

[Pikkon]

I have ran a snes off 5v just plugged into my pc so yes it should work.

So do you just want to wire up a usb?

Since the famicom has a 7805 you will want to start there,if you wanted to do it real quick solder the postive usb wire to the input and the output of the 7805,and ground is the middle and the power switch will not work as you would have to wire that up as well

Wow, a SNES! You didn't have problems with not providing enough current?

If I were to solder to the input and output of the 7805 wouldn't I have to take the regulator out as well? In any case, I was curious if I could bypass the whole RF board and power it up without it.

You can leave the 7805 in,it's not going to hurt anything.

As for the whole rf board the ribbon cable that leads to the motherboard has some 5v points,that should work.

[toadhall]

Awesome. Thanks for the feedback guys. I'll update when I get some time to experiment.

[Arkanix38]

No problem! Best of luck.