Can AC-DC Adapters break?

[Zerohero]

Hey All,

I've read the boards a few times and decided to make a post. I am a hobbyist and build small devices in my free time. For my current project I am using an old ac-dc adapter to power a series of fans for a diy laptop cooling pad and here is the problem: The label reads 12vdc1a but the actual output is 18v6a - is it possible for adapters to break like this? If I build a circuit to adjust the voltage for my load, can I expect the adapter to get worse over time (values increase/decrease)?

Thanks for any advice

 

[sijukrishnan]

How did you measure the 6A load? Sometimes, low quality adaptors possess more voltage than specified and voltage comes down to nominal if loaded with. This is because of poor load regulation. But in the given case, the adaptor is pretty much capacity of having 6A output current. So I think, the problem is with the label only.

 

[pranam77]

You didnt mention what type of power suupply is it. A transformer based or a SMPS one? Usually transformer based wall adaptors or such unregulated powersupplies tend to deliver more voltage without any load connected to its output. Try measuring with the load connected. When you say 1 Amphere is mentioned on it, it should be 1 or less than that or the vendor has sold the power supply at a loss as you may have paid the cost of 1 amp :wink: Practically this is not possible by 99.99%
Cheers

 

[betwixt]

If you measured 6A by connecting a meter straight across the output and reading the current, it may show 6A but the voltage would be dragged down to almost zero. there is also a good chance of damaging it if you leave the meter connected too long. If the 18V was measured in the same way, the meter would draw almost no current so you would be seeing the off-load voltage which on some supplies is quite a biit higher than the rated voltage. The voltage will drop as the current increases. The marked rating is probably correct, I'm guessing it gives a nominal 12V with loads up to 1A.

Brian.