[sdiy] Transformer hack, recommendation - or not

[harrybissell]

Its a one time (non resettable) thermal fuse. It allows the manufacturer
to get a 'class two' rating on a transformer that is really too large to get
the normal rating.

Normally its a matter that the transformer is 'impedance protected'
meaning if you short the output windings the internal resistance is high
enough that it will not go into meltdown. This allows them to not bother
with fuses etc. Wallwarts are normally class two, they may burn OUT
but will not BURN.

Larger transformers with the one time fuse can qualify was well. They suck.
I would go ahead and fix it (short circuit) but I'd watch out about leaving it

unattended.

I fixed a PA amp like this, but then kept it for myself. I could no longer
trust
it in a fixed installation where the power might be left on...er .... forever
???

H^) harry

KA4HJH wrote:

> >Hi list, a week ago my soldering station died on me
> >and while opening it up i discovered that the
> >transformer didn't give any output. While dissecting
> >the transformer i found a small white-ish part (like a
> >resistor but made of plastic?) on the mains terminals
> >that didn't conduct and seems broken.  So i removed it
> >and measured the transformer and it seems to be having
> >the right resistance now (58ohm).
> >
> >But! I also managed to cut a piece of the copper wire
> >on the mains winding so i did a hack
> >(www.sdiy.org/knas/temp/transformerhack.jpg) and i
> >wonder if this is just not recommended or really,
> >really stupid.
> >
> >The station crapped out on me after i had cleaned the
> >pen with red spirits, the fuse decided to not be a
> >fuse and blew the transformer. Also, if anyone know
> >what that white-thingy was it would be interesting to
> >know...
>
> I'd heard that the newer Wellers have a fuse of some sort in the
> transformer. Makes for an expensive repair. Also, the newer models (unlike
> the ones they made in the eighties) have a cheaper transformer that's more
> like to fail (or at least blow the picofuse or whatever the thing is).
>
> I'm guessing that's what's going on here...
>
> --
>
> Terry Bowman, KA4HJH
> "The Mac Doctor"