[XCSSA] Can you break transformers?

[X-otic Computer Systems of San Antonio]

>
>> 2) Use appropriate fuse on transformer secondary.  Generally slow-
>> blow is OK for big transformers, but little transformers might need
>> fast-blow and even that might not be fast enough.
>
> Secondary meaning the 12V side? I was thinking about that. Question
> is, do I put it before or after the regulator and/or caps? Seems like
> a requirement at this point :)

Yes, secondary is the 12V side.

Depends on what you want to protect from what.  If you're blowing  
your regulators, you want to put a fuse after the regulator.  If it's  
the transformer you want to protect, you can put it after the  
secondary.  (BTW, that's common practice in power amplifiers, or it  
used to be before they had computerized protection circuits).  Also  
fuses are often put on the primary side, that protects both the  
transformer and the house and the user (!) but problem with that is  
that primary side fuses generally won't be fast enough to protect the  
transformer secondary or anything else inside.  Legend is that fast  
blow fuse will always be protected by even faster blow transistors;  
that's not always true, but more true of primary side fuses than others.

With the way things are going for you, it sounds like you need fuses  
everywhere at least until you figure out what's going wrong.

I though you had a tiny 100ma transformer or something, a sneeze will  
blow those, but blowing a 3 amp transformer?!!  That's a pretty big  
deal.  You must have a short somewhere, or maybe the rectifier or  
caps are wired backwards, something on that scale.  I'm surprised you  
haven't been seeing the blue smoke.  I'd check everything really  
carefully before plugging in again.

>
> Well, I'm thinking of just buying a new one of Allied and being done
> with it. Not sure of those are fused or not though, but I'll go ahead
> and just add a fuse the next time around and be done with it :)

Big non-wallwart transformers aren't internally fused, or if they are  
it's at a much higher current.  The current specification for a  
transformer part is generally "working" rating which permits  
significantly higher peak currents.  It's intended that the circuit  
designer put in fuses and other design features (such as grounding or  
double insulation) as appropriate.  It's not a part that has to be  
safe for any
dumb end user.

But if you've got a bad enough short, you'll either kill the  
transformer, trip the breaker, or burn a wire or circuit board trace.

BTW, I think commodore external PSU's were not over-rated, and in  
I've seen dead ones before.  They just had barely enough output for  
use intended, and anything above that would blow them, just like  
cheap wall warts.

Charles