How is this possible?!? (Calling all electrical engineers)

[jgenotte]

FACT: NES requires 9V AC 1.3A

FACT: I have been running a 9V DC 800mA power supply to the NES for months without realizing it.

FACT: I has worked fine through many multiple-hour gaming sessions.

Question: DC instead of AC, how is this possible? I can understand it kinda working for a few minutes, but for hours and hours? WTF? Help?

ps: I know that I am an idiot and should, by all rights, have a broken NES, so please keep the idiot bashing to a minimum.

[FABombjoy]

The 9V AC from a stock NES adapter is first rectified (changed to DC) and then regulated to 5V.

By using a DC adapter, you're bypassing half of the rectifier array, but still providing 9V power.

The NES may not need as much power as the stock AC adapter puts out. OR, and I'm very unsure of this, the total rating of the stock AC may be at peak, not RMS (average) current. At any rate...

I(rms) = .707 * I(peak)

.92 = .707 * 1.3

So, if that's how the supply is rated, then 920mA isn't much more than 800mA.

[ClubNinja]

So, if that's how the supply is rated, then 920mA isn't much more than 800mA.

I'd go with that viewpoint as well... just as an unnecessary second opinion ;)

[jgenotte]

Why would nintendo do this when AC to DC adapters are so easy to come by? Is there a part of the NES that needs AC power?

[RichD]

Because the conversion from ac to dc and the power regulation at 5V are "not perfect" electrical processes, you get heat energy as a byproduct. It is possible the engineers decided to put the ac to dc in the power cord and the dc voltage regulation inside the game to spread the heat output around so no one area gets real hot.

[jgenotte]

RichD: The power cord doesnt convert AC to DC though. The NES itself converts to DC and steps down the voltage.

anybody else have any idea why they would have done this?

[FABombjoy]

There really are tons of possible reasons:

-Cheaper deal on AC supplies from mfr.
-Perhaps the design originally required AC, but last minute parts change negated it
-Lessen heat from power plug
-Because neither method is right or wrong