guitar speaker/tube challenge redux

[KA4HJH]

>  > Very dumb question - maybe I need to back up a few posts?
>  > How does a transformer "blow"?  I mean, what happens to it?
>
>Thermic overstress on wires, the wires usually blow up into a open curcuit
>on that coil. Ther thermal overstress causes parts of the insulation to
>quickly into gas state while the rest have just been transformed into a
>mechanical stress due to physical expansion caused by the heat. This forms the
>basis for an erruption, a bang, a blow... and all of a sudden you can smell
>a combination of ozone and various other unhealthy gas form of plastic burn
>residues.

I had no idea it was this exciting. I've had to replace quite a few 
in cable TV amps, and there's nothing like the smell of a "puked" 
transformer (smells like burning varnish). It doesn't help when some 
genius put the fuse AFTER the bridge and one of the rectifiers shorts 
(this was back in the days when surge protection was still an exotic 
luxury, rather than routine).

Terry Bowman, KA4HJH
"The Mac Doctor"

ICQ: 45652354