Technical and Repair Assistance

[133MHz]

What AC adapter are you using?

[Jero32]

Already got one......local store had one. So now I have 2 adaptors one with a proper rating for the fami (enough amps) and the same for the fds :-D

[133MHz]

I have the feeling that our friend GinoZX is using his NES AC adapter with his AV Famicom

[manuel]

That would be not so good.

[son_ov_hades]

So I'm a tech n00b, why is it that nearly everything will die when powered by the NES AC adapter but the NES will run on just about anything?

[ericj]

The NES adapter provides AC output but almost all systems require a DC input. The NES adapter plug fits into many other game systems.

[son_ov_hades]

Yeah but if the NES adapter outpus AC why can it run on say a Sega Genesis adapter?

[133MHz]

Because since the NES AC adapter puts out AC, the NES has an internal diode bridge rectifier to turn that AC into DC, which then gets filtered by the big filter capacitor and regulated down to 5V by the 7805 voltage regulator.

If you get DC into your NES (like using it with a Genesis adapter as you say), it will pass right through the bridge rectifier, unchanged. In fact the NES can run on AC, and DC of either polarity since the internal bridge rectifier will always convert the power to the correct polarity. The only way to blow up a NES would be feeding it a ridiculously high voltage (more than 30 volts).

If you get AC into a Famicom or similar, the alternating current will destroy filter capacitors and sensitive electronic components (remember alternating current oscillates between the positive and negative 50 or 60 times per second depending on where you live). Polarized electronics don't like when you feed them reverse voltage, they blow up if there's no protection. Since alternating current oscillates polarity so rapidly, it will damage stuff fairly quickly. Think of it as switching your console on and off 60 times per second WHILE reversing the polarity of the plug. Pretty nasty stuff .

Reversing polarity alone is just as damaging, but most systems come with some kind of protection. Most have a diode in series with the power input (a diode is like a one way valve for electricity, so if the power is coming in the wrong way, it won't be allowed to flow through the system), but don't count on it. Usually the first things to blow due to reverse polarity are the filter capacitors and the voltage regulator, and if you're unlucky, something else (like delicate chips) too. Other type of protection is a diode in reverse across the power input. This approach is a little weird but pretty effective. When the polarity is correct, the diode won't conduct (since it's in reverse), but when the polarity is reversed it will conduct fully, causing a short on the power supply (usually blowing a fuse or something), scaring the hell out of the user and protecting the equipment at the same time. Needless to say, this one's my favorite

In a nutshell, the main difference between the NES adapter and the Famicom adapter is that the Famicom adapter has the bridge rectifier and filter capacitor inside it, while in the NES it has been moved to the insides of the console. This gives the NES a fairly good amount of protection (it allows it to run on pretty much everything) while making the NES AC adapter a dangerous console killer.

Hope this helps. 

[ericj]

Excellent explanation. 

[son_ov_hades]

Thanks 133MHz, that helps alot.

[wentle85]

You should write up some more articles like this and have them put on the site. This was extremely helpful 133MHz. Thanks

[133MHz]

BTW a protection diode won't save your console from the perils of feeding AC into it. The diode will just rectify the alternating current converting it into pulsing DC, which again would be the equivalent of switching your console on and off 60 times per second. You wouldn't do that to your beloved Famicom do you?

That's why I say don't count on any internal protections. If you're testing polarity or whatever, switch on your console. If it doesn't work, or it displays rolling lines, buzzing, or anything weird, switch it off immediately.

Oh and BTW, please don't use your NES AC adapter for anything else than the NES.

[JC]

You should write up some more articles like this and have them put on the site. This was extremely helpful 133MHz. Thanks

We have plans for 133MHz and the stuff in these threads...the ball's in UglyJoe's court right now...

[GinoZX]

Thanks 133MHz for the expenation. I didn't know about the NES adaptor......I tried using it when I accidentaly blow up my original Famicom adaptor. I ordered a new Famicom converter and also gonna buy a better elektricity converter >.<

[son_ov_hades]

You used a NES adapter with a Famicom? Better start looking for a new Famicom too.