Famicom AC-Adapter and General Power F.A.Q.

Started by Xious, November 18, 2011, 06:54:54 pm

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November 18, 2011, 06:54:54 pm Last Edit: January 02, 2012, 04:20:19 am by Xious
This is a F.A.Q. for any Famicom owner, that is intended to cover what AC-Adapters (Power Supply Units, or PSU) can be used both safely and reliably, as well as general AC and DC power-related questions. I will be expanding this as time permits. Please reply with any related questions not covered in this FAQ and i will add and provide answers to them as appropriate to this document.


AC (Alternating Current):
The electricity form that exists in wall outlets around the world. The exact frequency and voltage will vary from country to country, which I will cover later.
DC (Direct Current): This is the form of electricity used by most electronic devices that contain integrated circuits, like the Famicom.
AC Adapter: This is the power supply unit (PSU) that you connect to your Famicom and then to the wall for power. It transforms AC to DC for electronic devices.
Stepdown Transformer: This type of converter lowers the voltage of electronic current, but does not change it from AC to DC or vice versa.

Terms used on AC Adapters:

Input Voltage: This is the voltage that the AC Adapter expects to receive into itself, that it will transform to DC current. it is measured in volts (V) or (VAC) and cycles (Hz). This is often expressed as a range, such as 110-120VAC and 50-60Hz.

Output Voltage: This is the electrical current measurements for the output voltage; the power that the AC Adapter is conducting to your Famicom. it is expressed in Volts (V) or (VDC) and Ampere (Amp) or (A).

Ampere are often divided into units of one-thousand (1,000th of One Ampere). These are called milliamps (mA) or (mAmp). Remember that there are 1,000 mA to 1A, so 500mA is 1/2 of 1A (0.5A)!

Polarity: The connector that attaches to your Famicom has a positive and negative terminal: The little barrel is charged one way inside, and the other on the outside; this is required for the proper flow of current. The direction of charge is expressed with either Centre-Pin Negative or Centre-Pin Positive, or illustrated thusly:

(-)------------(o------------(+)   ---   Centre Pin Positive
(+)------------(o------------(-)   ---   Centre Pin Nevative

The (o is a representation of the central pin (or core) of the barrel, where the line touches the circle or dot. Thus, ( is the outer portion of the barrel, and o is the inner portion of the barrel.

It is important to understand and be able to read these definitions when using an AC-Adapter.
Note: The original NES PSU has an output voltage of 9VAC! This means that it outputs Alternating Current, not Direct Current and will damage your Famicom!

Watts (W) are an expression of joules of electricity per second. The conversion of Amps to Watts at fixed voltage is easily found with this equation: Watts = Amps * Volts (thus, 1 Amp * 100 Volts = 100 Watts). The actual equation, for those interested is P = I x V.

Barrel Connector: This is the 'tip' of the AC-Adapter; the part that plus into your Famicom. It has two measurements: The outer diameter (of the round, metal shell) and the inner diameter (of the hole / centre pin). You can measure this with a set of calipers (or a micrometer, etc.) if you are unsure of its size, and you can buy barrel connectors with fixed measurements, correct to all FC models, from most electronic suppliers.

******Questions & Answers******

Q1: Can I use a normal NES AC-Adapter / Power Supply on my Famicom?

A1: No, the factory (Nintendo-made) NES PSU is not an AC Adapter! It is an AC stepdown transformer and outputs alternating current that will seriously damage your Famicom.

Q2: What type of Power Supply Unit / AC Adapter should (or can) I use with my Famicom?

A2:The specific and original AC Adapter for the Famicom and the Super Famicom has the following specifications:
Input: 100VAC 50-60Hz
Output: 10VDC 850mA
Polarity: Centre Pin Negative
Barrel Size: Outer Diameter 5.5mm; Inner Diameter 2.1mm

The Sharp Twin Famicom AC-Adapter is different. Its specifications are:
Input: 100VAC 50-60Hz
Output: 7.6VDC 1250mA (1.25A)
Polarity: Centre Pin Positive
Barrel Size: Outer Diameter 5.5mm; Inner Diameter 2.5mm

The Famicom Disk System AC-Adapter has the following specifications:
Input: 100VAC 50-60Hz
Output: 9VDC 400mA
Polarity: Centre Pin Negative
Barrel Size: Outer Diameter 5.5mm; Inner Diameter 2.0mm*
*Most 9VDC universal AC-Adapters will work in its place, as it can accept the same tip as the Famicom and the MegaDrive, etc. The factory tip is slightly different (and red!) to prevent accidentally using it on the Famicom.

If you live outside Japan, what all you need to remember is the Output Voltage and Polarity, as you can use any AC-Adapter with the same output ratings (or very similar) and the same type of tip and polarity.

The Famicom has some leeway in the voltage that it can safely accept. We call this the tolerance.

You can use a power supply that varies as follows:
Voltage Output: Minimum 9VDC Maximum 11VDC
Ampere Output: Minimum 700mA, Maximum: -Unlimited-
Polarity: Centre-Pin Negative (+)------------(o------------(-)

Ampere Notes: The FC will draw upon demand, so you can pretty much go as high as you need. You need to worry about covering the minimum rating here, and I suggest an 800mA minimum if you plan to use games with lots of extra memory or if you plan to use external controllers, etc. I would not try to use the 3D glasses, for example, without the full 850mA. Using less won't damage your hardware, but it may damage your PSU.  Others may suggest more or less, but much more will cause the system to overheat, as will be explained below.

Q3: What AC Adapters (other than the original) that I can commonly buy are compatible?

A3: The Famicom will run from a Sega MegaDrive/Genesis (Type-1) AC Adapter and the Sega Master System/SG-3000 AC Adapter, from your local area, with no need for a step-down transformer. (e.g., a USA AC-Adapter for people in the USA, or a European AC-Adapter for people in Europe, or a Brazillian AC-Adapter for people in Brazil, etc.).

Local AC-Adapters (designed to run on your local voltage specifications) of this type do not need a step-down transformer, as they are (after all) designed to be used locally. If you use one fro out of your area (such as a MegaDrive AC_Adapter from Japan, when you live in the U.K., then you will need an appropriate step-down transformer to convert the current, as normal.)

If in doubt, check the label on the AC-Adapter and look for its Input Voltage, then compare that to what is used in your locality.

You may also find aftermarket power supply units meant for those systems, or power supplies meant to be used on the four big consoles: The NES/SNES/Genesis/Mastersystem. These usually come with an assortment of configurable tips, and because they support all four systems (not merely the NES), they output DC current. (The NES can run on DC currrent too, but the stock Nintendo NES PSU outputs AC.) In fact, some aftermarket NES PSUs are DC-output... Just be sure to read the markings!

The PSU from the NEC PC-Engine/Turbographx-16 may also work.

You can also purchase an AC-Adapter that has variable settings: On these, you select the output voltage by some means, and the adapter has a fixed amperage rating. Look carefully at the output amperage when buying one, as they are often sold rated by maximum wattage, which is not very meaningful. Be sure to select one only if one of its settings is 9VDC or 10VDC out!

These usually have a switch (or a changeable tip) with which you set the polarity. Be doubly-sure you do so correctly, and that you understand how to use the product...

Q4 What about Japanese AC Adapters? They use a different input voltage than anything in my locale, so can I use them in my country?

A4: if you want to use an original PSU from Japan outside of Japan, you should buy a step-down transformer. This device converts your local AC power to that of another country. What you want is to convert whatever your local standard is to the Japan standard of 100VAC @ 50/60Hz. Some stores may call these voltage adapters, or voltage transformers, or something similar.

From the USA, you need to convert from 110~120VAC @ 60Hz to 100VAC @ 50/60Hz. I use this model, which is easy to buy in Amazon. I find that the VCT brand is extremely reliable, very affordable, and smartly designed. It has a pass-through port for local devices, and the 100VAC port for Japanese devices. This means that you can use both USA and Japan devices without losing an outlet.

You can also attach a splitter to it so that you may run multiple systems or devices from the transformer. VCT makes models ranging from around 250W to 2,000W or higher. I suggest the 500W model, or the 1,000W model if you want to run many systems, monitors or televisions from one transformer. Your Famicom alone draws about 8.5W at maximum demand1. (Double this to 17W1 with the FDS attachment.) Even with the FDS, you have an additional 483W of energy to use, so you can safely use even more systems on the 500W transformer!

If you add an old CR TV or monitor to this, deduce 100W; a small 14" to 15" CRT (such as a Commodore 1702) will use around 40W to 60W at maximum demand. Larger CRT displays may use as much as 100W, so i suggest that value as a precaution. Large CRTs, over 20", could use 150W or more as well: The actual wattage rating should be on the manufacturer's labels or markings, somewhere on the back of the unit.

Using a 100VAC AC-Adapter on 110-120VAC current (the USA standard, which we average to ~115VAC) may damage it over time. This can cause it to overheat, and can cause other internal damage to the AC-Adapter (for a more complex explanation, please read the replies in this thread), especially on newer aftermarket AC-Adapters, and may also be harmful to your system. Using a power strip (i.e. 'surge protector') does not help, in any way whatever. (It does not change the voltage on your electrical line!)

In short: Either use an AC-Adapter designed for local current, or get a step-down transformer. Otherwise, you risk trashing your hardware, or other problems that you may rather avoid.

I you live in Europe (or South America, or Asia, etc.), you will want to first check your local power standard. For example, in the UK, you will have 220-240VAC (~230VAC) @ 50Hz, and you should either buy a step-down transformer to convert directly from your standard to Japan's 100VAC @ 50-60Hz, or you can be sly and buy the USA-->Japan step-down transformer, and a step-down transformer to convert your local power to the USA 110~120VAC @ 60Hz standard. This may be easier than finding a transformer to convert your local AC current to the Japanese standard, an it will allow you to use USA devices as well.

You can, of course, always use an AC_Adapter designed for your country, as usual. If you are in Wales and own a Mastersystem, for example, you can use its AC-Adapter, or any AC-Adapter with the correct output voltage and amperage ratings.

You can use this chart to deduce your local rating.

1I need to verify that this is completely accurate. In theory, 8.5W is the maximum demand that can be put on the stock Famicom power supply; however the actual AC Adapter should draw more from the AC source, as it is not perfectly efficient. I suggest that it draws as little as 2x the specified amount, and that you should apply this as a safety margin. I apply a 10x margin whenever possible. The FDS stock PSU is smaller and usually has a tiny demand, but often a 10V 850mA PSU is used on the system, rather than the legitimate red-tipped PSU, so the calculation is based on the same rating as the FC PSU.


Nice article.
But are you sure about the "Famicom alone draws about 85W"?
I always thought it used only 4W. Or do I mix something up here?


November 18, 2011, 10:32:41 pm #2 Last Edit: November 18, 2011, 11:35:57 pm by Xious
There is a difference between the wattage of the Famicom (internally) and the FC AC-Adapter... It should be 8.5, and even then, I could be mistaken as to the exact wattage demand, as I don't know off-hand if the amperage demand the AC-Adapter has on the AC source is less than its output amperage. The FC draws 4.25W from the 7805 (at full/maximum demand), and the output power of the factory AC adapter is 8.5W (again, this is the maximum demand possible). Usually, the values will be less.  

If someone wants to measure the amperage demand that a stock AC adapter places on an actual 100VAC line, and finds me in error, then I can correct the FAQ. It's here both to be correct and to be useful, thus I'd rather overestimate for safety.  

Additionally, I will field any questions that people wish to ask in this thread, so if there is anything you think I should add to the FAQ, post about it and I.ll add it to the top.  :bomb:


I wonder about this:
Voltage Output: Minimum 9VDC Maximum 11VDC

I have heard people use both more and less... it was on the NES, but still? I do know people use 12 Volt adapter safely for it. Internally it uses 5V, so shouldn't any adapter over 5V be okay?

I'm not sure if you mentioned stablizied power supply in the FAQ. As far as I know, the adapter doesn't have to be stabilized (i e use a cheap one).
Edit: though I just found this article now: http://answers.yahoo.com/question/index?qid=20071012223554AAt543O It could explain a previous problem I've had.  :D

If there isn't enough wattage on the power supply, it may overheat, right? Still, I think 650 mA is safe.

Here is an article about measurements of power consumption by the way: http://nes-101.wikispaces.com/Power+Research
Selling  Japanese games in Sweden since 2011 (as "japanspel").
blog: http://japanspel.blogspot.com


Then more you have Voltage output, then more you will dissipate on 7805 regulator. According to datasheet 15 is maximum and at this voltage 7805 will not work stable and easily overheated. Bottom voltage is drop voltage of 7805(2V) plus some more on pulses of DC. Yes 1000uF can not give you ideally "flat" voltage, but you can not increase it - no profit, but heating coils of transformer and bridge. So... minimum voltage is around 7.5V with load, ah, also keep in mind your power company - how stable voltage in wall socket. If tolerance about 5-7%, then you need exactly 8V minimum.
I don't buy, sell or trade at moment.
But my question is how hackers at that time were able to hack those games?(c)krzy


Quote from: fredJ on November 24, 2011, 05:02:33 am
I wonder about this:
Voltage Output: Minimum 9VDC Maximum 11VDC

I have heard people use both more and less... it was on the NES, but still? I do know people use 12 Volt adapter safely for it. Internally it uses 5V, so shouldn't any adapter over 5V be okay?

This is what I deem the safe zone: If you drop much below 9VDC, you enter, as mentioned, an uncertain area regarding power fluctuation; 8VDC is acceptable, but not particularly what I'd deem wise; 7.5~7.6DVC is possible as well, however the frequency of such a PSU that you will find in the wild, that has the correct amperage and the correct barrel connector (with appropriate polarity) is essentially zero.

Going over 11VDC increases the level of heat generated by the 7805, and as heat is a byproduct of entropy, that boils down (pun intended) to lessening the lifespan of the 7805. You also risk thermal overload of other components, although the chance is slight, as you apply more voltage, as heat spreads uniformly, and the 7805 is not fully isolated. You should also keep in mind that the FC, in addition to 5VDC internal, has direct unregulated voltage as well, and this expects to be 9~10VDC.

I'm not sure if you mentioned stablizied power supply in the FAQ. As far as I know, the adapter doesn't have to be stabilized (i e use a cheap one).
Edit: though I just found this article now: http://answers.yahoo.com/question/index?qid=20071012223554AAt543O It could explain a previous problem I've had.  :D

If there isn't enough wattage on the power supply, it may overheat, right? Still, I think 650 mA is safe.

A regulated PSU will supply cleaner, consistent current, which equates to less noise, and using a non-regulated PSU will affect some components, such as the PPU. (This can affect your video quality, as an important example.)

Insofar as lowering your PSU amperage, it is possible to drop to 500mA, but I would not by any means suggest or advise it, and anything that is ill-advised doesn't belong in the body of a FAQ. If you run a system with a 650mA PSU, and try to run external devices (such as the 3-D system, which draws ample amperage, and has a pass-through for a second set of glasses), or other external controllers, or games with additional CHR-RAM, etc. then your load will exceed the maximum demand on your AC adapter, causing thermal overload.

Have you ever seen a PSU literally split apart and billow out black smoke? I have; in fact, I recently saw that happen when using a 12VDC compressor on a 110VAC-->12VDC adapter that didn't supply enough current. It (the AC adapter) actually split apart and burst aflame. You can't have too high a maximum amperage demand rating for this application, but too low of a demand is dangerous, both in terms of damaging equipment, and as a fire hazard.

Imagine leaving the system on and going out for a cuppa only to come back home to a charcoal flat. That's not what we want to advise here. ...

Thus. no, you really do need the correct amperage (which is not identical to wattage) and I would not vary the voltage outside of 10% of design specification, which is a normal tolerance for many consumer-electronics systems.


Here is an article about measurements of power consumption by the way: http://nes-101.wikispaces.com/Power+Research

My FAQ is given to supply safe and accurate information. People will do what they wish, but I want to ensure that they don't destroy their equipment or have any other, grander problems arise from the information therein. Hopefully this clears up any questions you may have on why I gave that specific range of numbers.

I don't recall off-hand which (if any) attachments or devices use the unregulated voltage, but assuming that any exist, it would be even more important to stay within a certain threshold. Anyone that knows of something that uses this FC capacity should post about it in this thread so that it is directly referenced (pretty-please). :bomb:


Now my question is if I use the Sega Genesis Type-1 Adapter will I also need a stepdown adapter still or do I only need a stepdown converter if using a Japanese AC adapter?
Famicomman handle used since 2005
First Famicom Purchased December 12, 2011


Isn't it true that Famicom AC adapters are built for the Japanese standard, which was 100V 50/60?  The eastern half of Japan does indeed use 50Hz but the west (where I live) uses 60, just like the US.  I think since the US standard is 120V 60, you could safely use an original Japanese Famicom AC adapter in the states, though your machine would run a little hotter.

(I've talked to several friends who had returned and safely used small appliances with much higher wattage draws such as toaster ovens and denki pots with no problems.)


December 14, 2011, 02:07:56 am #8 Last Edit: December 15, 2011, 09:06:53 am by Xious
Running an AC Adapter designed for 100VAC on 110VAC will, over time, damage the AC Adapter, at the least: It is not safe for the hardware. They are however, 50/60Hz. :bomb:

P.S. I updated the 50/60hz issue: I had specified the Japan current as 50-60Hz  at one point in the F.A.Q., but earlier I only noted it as '50Hz'... It is now clarified, and I did some clean-ups, added additional information preemptively, as well as adding information regarding another question (i.e. clarifications) that I was recently asked.


Good work on the FAQ thus far.  I don't think I've said "thank you" yet ;D

I've been meaning to post the specs from my PC-Engine adapter, as you mention they "may also work".  They're not 100% the same, but may be close enough.


No worries; you are quite welcome. I thin this has saved the forum from the normal PSU questions assault, as FW was averaging at about one question per 3-4 days for a while, most of them the same or very similar in nature. I think I'm hard-pressed to come up with any more questions to answer, but I expanded it a bit today, clearing up a few matters, and adding the information to cover the 'local Genesis MK-1' question that I answered in another thread in the last day or three.

I'll continue to expand it as is needed to fit the demand of questions, even the esoteric ones. Why not, right?

My reason for the wording the the PCE/TG16 AC-Adapter is due to its lower amperage. I think that it may overheat, or fail entirely, if you try to run it on a system that carries any burden, such as the 3-D system (or two of them), additional controllers, of hardware-heavy games. IIRC, it is 650mA or 700mA maximum demand, which is 150mA to 200mA short of the maximum demand of a factory PSU.

Sure, on a basic system it will be fine, but I wouldn't run one on my system, which has a 3-D system and/or an external controllers on it much of the time, plus a PowerPak, which draws a deal of current for its support hardware.  :bomb:


Re : Japanese Famicom PSU on US power

The PSU is 100V to roughly 10V a 10:1 ratio, if you put 115V through it you will get 11.5V. Although the output voltage under load is going to lower. The Famicom PSU is also unregulated. Unregulated means if you do not draw a certain current from the PSU then the voltage will go up, measure a Famicom PSU without load and it will be much higher then 10V. However the Famicom with eh 7805 and other components means that it will draw enough current that the PSU will not drive more votlage into the machine.

Most transformers are designed to work within a wide tolerance because you are never going to get 100V perfectly in every home, under load the wall socket in my Japanese place is giving out 108V AC (the PSU is giving 10.6 volt under load). 120V is well within the tollerance level. Although the US power is nominally 120V as a lot of places are 110V or 115V.

In Europe, nominally the voltage shouldbe 230V, although it does vary from 220V to 240V, although you are likely to mesure between 210V to 250V, although the connectors may be different the PSU in europe is generally the same for games consoles and they have a much higher voltage load to deal with, however the 7805 will regulate the voltage.

I've used a number of Famicom PSUs both with US and Taiwanese power as well as using a 2:1 step down (so 240V in 120V out) and these on on Famicoms that are on 8 hours a day, 7 days a week, at least 6 months a year for the last 6 years at least and I've not had a FC break down or a PSU fail. Yes the transformer is working harder with a higher voltage as is the Famicom but in the grand scheme of things it is not going to make much difference.

So someone is going to ask why 100V <> 120V devices exist and it is because there will be devices that have a much lower tolerance and could be damaged with the higher voltage going in. Also plugging a 120V unit in 100V is more likely to draw excess current and this is generally what will cause PSUs to fail. Although this generally does not apply to transformer based computers and consoles as the transformer generally will work to the tollerance.


Wait, I was checking and noticed that my SNES AC adapter has these ratings:
Input AC120V 60Hz 17w
Output DC10V 850mA
(+)------------(o------------(-)  Center Pin Negative
So I'm assuming it would work as well, right? Why is it not mentioned in place of the Sega MK-1 adapter when it is much more likely someone will have an SNES adapter laying around? Would the SNES adapter also work for the Super Famicom?
Famicomman handle used since 2005
First Famicom Purchased December 12, 2011


The barrel plug on the SNES adapter is a larger diameter than will fit into a Famicom. Otherwise, it would be a good substitute.


I can say the barrel plug for the snes is the same on a super comboy.