# Question on replacing a power adaptor



## 1dave123 (16 Dec 2011)

Hi there

I need to replace the power supply to my Eircom Netopia 2247NWG Router. The power supply says 

ac/dc adaptor
input 230v ~ 50hz 110mA
output 12.OV 800mA 

From various searches of the internet I understand that the replacement must have the same volts (i.e. 12v) and the AMPs must be higher than 800mA (0.8A). 

I tried an existing plug which has the following written on it 

AC Adaptor
Input 100-240v ~ 50/60Hz 0.8A
Output 12v 2.0A

I expected this to work as it seemed to meet the criteria - but it didn't. Any ideas? Is the fact that this plug says AC Adaptor rather than Ac/Dc adaptor significant perhaps?

Many thanks indeed


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## alexandra123 (16 Dec 2011)

I have a spare one if you want it ? You would have to pick it up as it would be a bit heavy to send in the post !


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## 1dave123 (16 Dec 2011)

Hi Alexandra123 - thank you for your kind offer. You're very good.  I should be able to pick up one pretty cheaply once I know what I need. I am as much interested in why this other plug didn't work as anything. My knowledge of electrics is pretty minimal. Thanks again tho.


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## alexandra123 (16 Dec 2011)

No problem, it is probably not working because the input voltage is too low..It might not be getting enough power to it for it to function correctly, but I am not sure !


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## chrisboy (16 Dec 2011)

Why do you think its the adaptor?


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## Guest125 (17 Dec 2011)

There are other criteria that need to be satisfied for the adapter to work. 1) Polarity,a diagram will be on the adapter with + and an arrow either pointing to the center of the pin or to the outside of the pin,this is very important. If the replacement adapter has its +(positive) the wrong way around i.e. on the outside instead of the inside the router will be destroyed instantly. 2) The internal diameter of the adapter hole must be the same as the original or it won't make contact with the pin in the router.


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## 1dave123 (17 Dec 2011)

Hi - a fair question, chrisboy. But it is definitely the adaptor rather that the machine. 

Thanks Caff. The diagrams on both are the same.  Good point re the internal diameter tho. I think that might be it. They look the same and the replacement fits snugly into the router .... but as a further test I switched them around and tried the router adapter in the machine I got the existing plug from .... it doesn't fit!

Well done - I think you solved it


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## Leo (19 Dec 2011)

1dave123 said:


> Is the fact that this plug says AC Adaptor rather than Ac/Dc adaptor significant perhaps?


 
The AC adaptor may be AC/AC, so just reduces the voltage (output is alternating current) rather than reduce and convert it to DC (direct current).

Does it state AC or DC alongside the output voltage, or does it display any symbols such as a sine wave (~) or a line in parallel with three dashes?

Another inportant consideration is whether the proposed supply is regulated or not. An unregulated supply cabable of delivering 2A at 12V will likely output more than 12V driving that load.
Leo


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## 1dave123 (19 Dec 2011)

Hi Leo

There is no mention anywhere on the replacement power plug of DC.

The output looks like this 

OUTPUT:12V 2.0A. Between the V and the 2 are two lines. The upper line is straight and the lower line is a ---.  Does this imply DC output?

The ~ symbol does appear on the input line as ... input 230v ~ 50hz 110mA

I have been reading about unregulated v regulated .. but I cant find the words regulated or unregulated anywhere on the power supply ... perhaps this means the power supply is unregulated?

Ta.


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## Leo (19 Dec 2011)

1dave123 said:


> The upper line is straight and the lower line is a ---. Does this imply DC output?


 
Yes. That's the international standard symbol for DC.



1dave123 said:


> I have been reading about unregulated v regulated .. but I cant find the words regulated or unregulated anywhere on the power supply ... perhaps this means the power supply is unregulated?


 
That one is less clear, it's often not stated.


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## 1dave123 (19 Dec 2011)

Hi Leo - one last q.  I have PC speakers and the old power supply (now damaged) was 15v and 0.8A.  I tried a new power supply that delivered 12v and 2.0A.  It worked and my understanding is this is ok.  Because the volts on the power supply was less than 15v it won't do any harm to the speakers. Is my understanding correct? .. or am I likely to create a problem for myself. Thank you


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## Leo (20 Dec 2011)

Hi 1dave123,

I wouldn't recommend that. With the lower voltage, you're likely to overload components in either the speakers or the supply. You can buy replacement power adapters in Maplin.
Leo


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## 1dave123 (20 Dec 2011)

Thanks Leo


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## Guest125 (21 Dec 2011)

The straight line and dashed line is actually the symbol for rectified ac not dc. I've never seen an adaptor that is an ac/ac converter only ac/dc. The idea of rectifying the ac input before getting to the router is to avoid the need for a rectifier pack within the router thus keeping heat/costs down.


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## Leo (3 Jan 2012)

IEC are the international governing body for electrical symbols. This symbol (S00004) is their standard symbol for dc, not rectfied AC as you suggest. 

The symbol for a rectified current with an alternating component (S00076) is a wavy line (~) over three dashes.

AC/AC adapters are common, even Maplin sell a range of aftermarket replacements.


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