Repairing wall warts

[Tony Duell]

> 
> On 2/16/2006 at 12:27 AM ard at p850ug1.demon.co.uk wrote:
> 
> >Very few wall-wears (at least the ones sold over here) contain fuses any 
> >more. The transformer is designed to burn out in a safe way if 
> >overloaded, or so I am told -- personal experience suggests it does not 
> >do so before the case has started to melt and smoke is coming out!
> 
> That's pretty surprising to me, considering that most UK appliances seem to
> have a fuse in the mains plug (almost every one I've seen has been 13A, yet

Yes, the standard mains plug over here is rated at 13A, and contains a 
cartridge fuse (nromally, 3A, 5A, or 13A). Obviously PSUs with a mains 
cable are fitted with such a plug which contains a fuse (even moulded-on 
mains plugs [1] have a fuseholder and fuse)

[1] %deity I hate those things. I've had all sorts of problems with them, 
from live/neutral reversed, to no strain relief on the cable... I cut 
them off and put a rewireable plug on the cable.

But wall warts seem never to contain fuses, relying instead on the 
transformer burning out in a safe way. Since the fuse in the fusebox is 
generally rated at 30A, I am not very happy about this.

I never use wall warts for homebrew projects. I build my own PSU, with 
fuses all over the place. OK, I can't stick an approval label on it, but 
I am darn sure it's safer.

-tony