Power Adapter Help

[fazersharp]

Woke up this morning to a dead modem, so swapped adapter and all is working.
But when i tested the non working adapter it reads 11.8v, it has been used for about 2 -3 years.
The replacement working one reads 12.2v.
What I dont understand is the one that now dosent work - how come it is not just dead but instead now reads 11.8v and how come that is not enough for the modem.

The modem rating is 12v 1A but the original matching adapter whent kaput was replaced with (the now also non working 11.8v one ) which has a rating of 0.8A so am I to understand that the max pull of the modem is 1A but the adapter I was useing could only deliver 0.8 max and so I have burnt it out, -- only I havent because  it still gives 11.8v.

The modem is running right now with a 12v 0.5A adapter should I be worried and should I get a 1A one
Any Help out there Please

[slimwilly]

It may not be the live,power out thats failed,could it be the neutral,negative side thats out?

[fazersharp]

Thanks for that slim, how can I test that. (not that I understand )
I now have the modem running with a 12v 0.8A adapter.

[characticus]

11.8V when not connected to modem does not mean it'll still be at 11.8v once connected. You need to check it under load. Chances are the voltage would then fall hence modem doesn't work. Unless the modem states on its case what current it draws the only way you can check is to measure it. Presumably its no more than 1 amp since the original adapter was rated for that. 0.8A is probably ok - but there are also plenty of crap (fake) adapters about on Ebay etc that are best avoided.

[fazersharp]

The modem is rated 1a I previously in 2010 the adapter for that packed up which was 1a and I replaced it with the now also packed up 0.8a.
I have it now running on another 0.8a adapter

I have an 8v rated adapter for a radio and just to see I tried it and the modem worked with that.

So under load are you saying that the dodgy adapter that reads 11.8v would be less than 8v

[characticus]

Yes. Probably is. Although there are other ways it could fail with those symptoms that's the most likely.

[fazersharp]

how much of a risk am I running using a 0.8 rated adapter against a possible max load of 1a on this modem huewei hg520b, considering the last adapter was also 0.8a and lasted 5 years.
Also where can you point me to non crappy cheep ones

[darrsi]

Put it in the bin......and buy the correct one for the job......sorted.

[characticus]

If you want to avoid fakes I'd avoid Ebay go to somewhere like CPC or Rapid Electronics. Try

http://www.easyflip.co.uk/CPC_2014/?page=1744

[fazersharp]

Put it in the bin......and buy the correct one for the job......sorted.

I ride a 17 year old bike --- that is not in my nature.

If you want to avoid fakes I'd avoid Ebay go to somewhere like CPC or Rapid Electronics. Try

http://www.easyflip.co.uk/CPC_2014/?page=1744

Thats a great help thank you and the thing is they are cheaper than ebay 

[bigralphie]

Its likely you have voltage with no real current
1amp is the max it can consistently supply but it will supply whatever is demanded up to this fiq (and a bit)


yea they are ok that CPC lot 

[fazersharp]

Glad I found this because I had forgot what I did wven though it was only last feb
Any way after 10 months the 0.8 adapter has now packed in so I am going to buy a 1A rated one
This one http://cpc.farnell.com/pro-power/pp10005/ac-dc-power-supply-12v-1000ma/dp/PW02709
But before I do it says 1000ma ----that is 1.0A (isnt it ) it also says 12w but the modem dosnt say anything about W     

[Frosties]

1000ma is indeed 1 Amp and 12w sounds right. Power (watts) = volts (12) x amps (1).


Good luck with this one Sharpy.

[fazersharp]

Thanks for that
It sounds stupid now but CPC list one as 0.5A and another at 500ma 

It looks like using a 0.8a max adapter on a 1a router has resulted in the adapter failing after 9 months or does it not work that way ?.
I have now ordered a 1a 12v adapter.
The modem is running at the moment with a 0.5a 12v adapter which i will replace with the 1a sa soon as it arrives.

Im still abit confused, I have two identical HG520b routers both say 12v but one says 0.5a and the other says 1a
As I understand it the adapter will only supply whatever amps the router asks for, so is it ok to use a 1a adapter with the 0.5 amp router and for that matter a 5a 12v adapter as the 12v is constant but it will only supply the amps that are asked for so it wont supply 5 amps to a 1a router
But then not a good idea to run the 1a router with the 0.5a adapter

[Frosties]

Thanks for that
It sounds stupid now but CPC list one as 0.5A and another at 500ma 

It looks like using a 0.8a max adapter on a 1a router has resulted in the adapter failing after 9 months or does it not work that way ?.
I have now ordered a 1a 12v adapter.
The modem is running at the moment with a 0.5a 12v adapter which i will replace with the 1a sa soon as it arrives.

Im still abit confused, I have two identical HG520b routers both say 12v but one says 0.5a and the other says 1a
As I understand it the adapter will only supply whatever amps the router asks for, so is it ok to use a 1a adapter with the 0.5 amp router and for that matter a 5a 12v adapter as the 12v is constant but it will only supply the amps that are asked for so it wont supply 5 amps to a 1a router
But then not a good idea to run the 1a router with the 0.5a adapter

Got it in one Sharpy - any device be it a PC router or a 3Kw heater will only draw the current they need......unless they develop a fault. My PC all runs through a 5 amp plug in RCD so if any issues arise the RCD will trip and cut the power.


"But then not a good idea to run the 1a router with the 0.5a adapter" - Definitely not a good idea. The 1a router NEEDS 1a so will try to get it from the 0.5a supply. The 0.5a supply will have a bit of tolerance but ultimately will overheat and fail.

[fazersharp]

Thanks for that.Begs the question of why then do they make 12v .03   0.5  0.8 1.0a  and so on why not just say 12v 5a which covers loads
I have now swapped the router to the 0.5a one I had and is running with the 0.5a adapter.
The original router was 1a and a few months later I brought a second hand spare one which was the newer and now 0.5a rated one

I assume that the 1a is its max and most of the time it will be less and even less than that when I am not typing on this forum