Transformer question (only slightly OT)

[jpero at sympatico.ca]

> > Wall warts, least here in USA must be fused internally or have a thermal
> > interupter (usually the blow open).  I've forcably opened a number of 
> > warts to replace protective devices.
> 
> I've opened up many wall warts over here and found the the transformer 
> primary winge goes straigh to the tags on the transformer (no obvious 
> connections to a fuse or thermal fuse) and those tags are wired straight 
> to the mains plug pins. And yes, said wall wards have various approvals 
> written on them.
> 
> I was told that the transfromer primary is supposed to fuse safely in the 
> event of a fault. My experience is that it doesn't (I've had shorts on 
> the output side cause the plastic case to deform and much magic smoke to 
> come out, but the transformer primary was still continuos after I turned 
> the power off. I did not feel like seeing if it would ever fail).
 
> -tony
>

Actually, fire came close for mine.  :O

I had DSL modem's big ceramic capacitor short out across the 16V AC 
input and fry the wall wart transformer.  Cut it open, interior all 
smelly and softened, primary winding opened where wires attached to 
blades. Exterior is mint. 

Fixed this with a junk VCR gutted except for transformer with a fuse 
& new ceramic capacitor in DSL modem.  Been this way for 3 years.

Cheers, Wizard