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

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

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Two other things that should be mentioned in the FAQ,

The tip for the Famicom / Super Famicom should be 5.5mm outer tip size, 2.1mm inner hole.

Order codes for the UK and the US are

Maplins (UK) order code - AQ88V (Power Tip E)
Radio Shack part number (US) 273-344 (Adaptaplug M has a blue tip)

Although most power adapters with the 6 or so tips come with the correct tip.

Another thing to mention about unregulated PSUs is that if you use a PSU that has a higher amperage rating then what the device draw then the voltage can be higher then 12V, I have seen a PSU output 19V when it was meant to be supplying 9V just because the device was drawing a lower current then what the PSU was rated for.


Hmmm but 9V 1A unregulated PSU is still safe for the famicom, right? That's what I use and sell.
Selling  Japanese games in Sweden since 2011 (as "japanspel").
blog: http://japanspel.blogspot.com

Da Bear

fredJ: I think your adaptors in fact ARE regulated. Measure the voltage when they are under load, and when they are not. It'll shows the same value. E.g ~9V
Always measure the voltage before you sell them to be on the safe side :)


9V at 1A unregulated should be fine as the voltage increase of the PSU of it being used with a Famicom will be tiny.


Pretty much. I need to check a factory adapter to verify if it is or is not regulated, but I seem to recall that it is not.

I so still stand on the point that a step-down transformer is a wise precaution. Not all PSUs have a high tolerance, and the industry standard is often +/-10%, not +/-20%.The excess heat is also a long-term issue, again majorly for the PSU. I see no reason to damage old-stock parts, and the slim chance of overheating, and causing a fire, means that I will mention it as a safety precaution in the FAQ.  :bomb:


December 28, 2011, 12:44:56 pm #20 Last Edit: December 28, 2011, 12:50:54 pm by fredJ
I agree with you. I also recommend that.

Since so few famicom users have the 3D Glasses, I think it is good to mention that specifically as you do.

Anyways, the suggestion for a PC Engine power source could be misleading. Pc Engine needs far less ampere. The standard adapter is DC 9V 650mA http://www.digitpress.com/forum/showthread.php?t=93487

Another question, what is best to do in case the adapter catches fire or melts? Suppose it is mounted to a wall. Can I pull it out?

And yet another thing. What happens if the polarity is wrong? I usually test PSU polarity on my SFC console, it only starts with the correct polarity. So I know it is safe to try on. If I use the wrong polarity on the Famicom, will it break?

Oh, and while I am at it. Is there a difference between heavy PSU units, the way they all were built back then (500 grams!), and the light modern ones (<100 grams)?
Selling  Japanese games in Sweden since 2011 (as "japanspel").
blog: http://japanspel.blogspot.com


Quote from: fredJ on December 28, 2011, 12:44:56 pm
If I use the wrong polarity on the Famicom, will it break?

Most likely it'll cause the large capacitor on the RF/power board to blow. If that occurs, the capacitor can be easily replaced and the system will be fine afterwards. It may also fry the 7805, which is also an easily replaceable component. Always remember to mind polarity when trying out power supplies, and you'll save yourself some grief later.


December 31, 2011, 03:31:39 am #22 Last Edit: December 31, 2011, 04:14:33 am by Xious
Possibly; it could also do nothing, at least if done briefly. It's nowhere near as harmful as applying AC to it. I can always test this to verify the results but don't expect me to do so immediately.  8)

To answer Fred's other question: The lighter adapters are 'switch mode' power supplies, whereas the older and heavier type use linear transformer circuits. In theory, the SMPSUs are less thirsty, but I personally prefer the power curves on the older models, not to mention that linear transformers are more resilient all-round, and are more likely both to survive a surge (or overheating) as well as less likely to pass that shock to the device they are powering.  :bomb:

P.S. I added the barrel connector measurements, as well as the definition of the term for the Famicom PSU, plus the specs for the FDS and Twin system PSUs. I will add the Titler PSU when time allows, although this is largely pointless, given how specialized it is.

I will also need to verify the barrel size of the FDS PSU with my calipers.it may be 5.3 or 5.7mm by 2.1mm instead of 5.5mm by 2.0mm. I just remember that it is slightly off in either direction to prevent crossing over.  :diskkun:


Quote from: Xious on December 25, 2011, 02:00:59 pmI so still stand on the point that a step-down transformer is a wise precaution. Not all PSUs have a high tolerance, and the industry standard is often +/-10%, not +/-20%.The excess heat is also a long-term issue, again majorly for the PSU. I see no reason to damage old-stock parts, and the slim chance of overheating, and causing a fire, means that I will mention it as a safety precaution in the FAQ.  :bomb:

There is a slim chance that plugging any PSU in to the wall will cause a fire. Although I think you should add, People should as a precaution unplug any PSU or plug from the mains when they are not using them as they do use some electricity and it reduces the risk of a fire if the device fails. I have seen PSUs fail, all cases have been cheap chinese PSUs.

You sort of emphasise that "Using a 100VAC AC-Adapter on 110-120VAC current (the USA standard, which we average to ~115VAC) will damage it over time.", however do you have any evidence at all that this would be the case? Ther is not much to the FC PSU, a transformer, a bridge rectifier and a cap, all of which are rated at a high enough voltage that even if 12V went through them they would not be stressed.  I do understand the use of caution but you do make it sound like if you do not use a 120>100V step down then your house will burn down and frankly in my experience that is just not true.

As mentioned before I do have FC (and Japanese megadrives) PSUs running off 110V to 120V (depending on location) and they are running at least 8 hours a day, 7 days a week for at least 6 months a year, and these have been running for between 9 years (one has and it will be 10 years come may) to a year (so all in all, probably a lot longer then the average person will use a FC) and it is not like I am using 1, I do have about 6 FCs running plus 5 Megadrivers. I've not had any issues with overheating or any of them failing (or indeed any of the FCs failing...), in fact the multivoltage PSUs I use have broken down but the FC and MD ones are working fine and are certainly more bulletproof then the

Still nice that you added Barrel lengths and sizes. :)


January 02, 2012, 04:09:53 am #24 Last Edit: January 02, 2012, 01:57:55 pm by Xious
People are welcome to use whatever they wish. The design of the factory PSU for the Famicom is certainly more durable than others; however, you aren't taking into account that people import systems that arrive with aftermarket adapters, including poorly made brands and horrible little switching adapters, and not all of them are rated with a high tolerance.  

This doesn't mean that old-stock adapters are fine and dandy to use in my book, as the potential chance of damaging the caps and the additional heat (and thus additional entropy) will shorten the lifespan of the parts over time, even if that means over thirty years. Aye, I have PSUs that are far older than that still in operation, and I prefer to keep them thus.

I also have to consider that any traditional design that either uses a cheap rectifier, or forgoes one will have a different ripple on 110-120VAC/60H than on the Nippon standards, which may also cause issues, and that a stepdown transformer will (or should) ease the effect of that problem. Even with the 7805, this can affect video performance / noise, and may cause certain amounts of system faults, although these are generally only temporary, from the same line noise issues.

The damage is primarily to the electrolytic cap in the PSU: Yes, I have seen evidence of this, often in increased video distortion, causing increased ground-plane noise from a dirtier signal off the PSU supply-line. Badly-made adapters could have more serious problems as well. Remember also that I can't assume that people are using a factory adapter, or even know what one would look like. I get FC systems--even boxed/complete systems--all the time that include an aftermarket PSU.

I can of course change 'will.to 'may' in that statement, and clean it up a tad ;) I will keep my recommendation there, and people who wish for more details may read the thread. It's rather beyond the scope of the F.A.Q. to discuss things like power-rail noise and frequency distortions in its body...

On another subject, I'm not sure why Sharp used such odd ratings for all of their equipment. The AN-50X-series use that nutter rated at 7.6V/1.25A, and the AN-510 has a dual-voltage set-up with one GND and two voltage pins; something like 14V and 9V, but not so simple, on a bizarre connector. I don't even see the practicality of the 7.6VDC PSU for the Twins, however I suspect that it is to lessen the heat output on the voltage regulator, from running all that HW on one AC adapter.

Why the two voltages are mandatory on the 510 (Titler) is a question for another day, when I have more sanity to spend dissecting one of my units. I could also use some news on that C1 and the other Sharp objects, if you've any.  :bomb:

P.S.  I made some modifications: I gave a slightly expanded and reworded explanation of the logic behind the stepdown transformer, as well as directing people seeking more technical information to read the thread. Further, I cleaned the definitions for the barrel connectors somewhat, and did some other tidying.


Most aftermarker PSUs are trash, I am surprised that it is not one of the questions in the FAQ... even PSUs that seem to output the correct voltage have a maximum current draw as much as the Famicom and have the correct input voltage can still go up in smoke.

The first thing that tends to go in the PSU is the smoothing cap drying up and causing ripple but you would get this regardless over years of use. Japan uses 100V at either 50 or 60Hz AC (for most transformer based PSUs the ac fequency does make little difference) depending on where you are in the country. However the frequency makes little difference as the smoothing cap does clean up the ripple, mostly anyway.

The Sharp Twin Famicom probably uses a lower voltage so it can get a larger current output without increasing the wattage, most voltage regulators will happily work at 7.5V anyway. The PSU has a maximum wattage of 9.5W which is only 1W higher then the FC PSU...

The wording to may is better but it is still scary to someone reading it, where it should be a gentle warning not a doom and gloom wording.

One thing you are missig which I think is worrying is about third party and multivoltage PSUs, first you do not anywhere make any note between regulated and unregulated PSUs! Secondly the maximum amperage you should use should probably no be any more then 1.2A as there is no reason to have more then this.

On these two points if someone used a 10V unregulated PSU rated at 3A then someone using it might be surprised when their Famicom goes pop as the unregulated PSU wil probably have a higher voltage if there is not anywhere near the rated amperage being drawn from the PSU.

With multivoltage PSUs you should buy a more expensive regulated PSU, you may also need to look at the current that can be drawn from the PSU at 9V to 10.5V, some will be advertised as 1.5A PSU but then you notice that is only for 3V at 9V it drops to 500ma.


Short question. Is there an european console PSU that will work  with the Twin Famicom. Could a PCE-Duo (i have a custom made) or PAL TGX powerbrick do the job? I'm a bit clueless about those technical things^^'


January 13, 2012, 04:39:36 am #27 Last Edit: January 13, 2012, 04:55:02 am by fredJ
No the PCE Duo is wrong afik, I don't think it fits.
The PCE-Duo is center positive according to my own original adapter for that console. Mine outputs dc9v 1000mA so it should match the Twin. But the plug size is much smaller on the PCE-Duo.

The Twin has different polarity from most other consoles. However, most ordinary PSU have the same polarity as the Twin has. Check what you have and make sure it has the correct voltage and ampere that are listed in the FAQ.
Then all you need is a little chord to go from the ordinary 2.1 mm to the twins 2.5. On eBay such chords cost 1-2$.
Selling  Japanese games in Sweden since 2011 (as "japanspel").
blog: http://japanspel.blogspot.com


Quote from: fredJ on January 13, 2012, 04:39:36 am
But the plug size is much smaller on the PCE-Duo.

Actually the Duo tip is much bigger than on the Twin Fami. The Duo's measurements are 6.3 mm by 3 mm, whereas the Twin's are 5.5 mm by 2.5 mm.


For an aftermarket Twin PSU with close to correct ratings, you can use (IIRC) a PSOne adapter (7.5VDC) and replace the tip. I don't however recall what the amperage rating of the PSOne PSU is, so this may not be acceptable. I have used (polarity reversed) generic console PSUs (e.g. MegaDrive type) on the Twin, however other people have made claims of problems doing this, which I have experienced seen in practice.

I use a stock Sharp adapter on my main unit, and on my bench (for testing and restoration/repair), just to be safe.  :bomb: