Kinda OT but that what's true HW hacker do in a pinch.

From: Don Maslin <>
Date: Sun Jan 20 19:38:31 2002

On Sun, 20 Jan 2002, Tothwolf wrote:

> On Sun, 20 Jan 2002, Tony Duell wrote:
> > And sometimes the primary is designed to be the thermal fuse. If it
> > overheats, the insulation melts, you get shorted turns, and it either
> > melts the wire or blows the current-operated fuse. Apparently the
> > former (wire that's designed to melt after the insulation has melted)
> > actually meets most safety approvals, and it's the intended failure
> > mode of most cheap wall-warts over here. Is it any wonder I can't
> > stand the darn things?
> The 9V AC wall-warts that are sold with USRobotics/3Com modems are made
> this way. I had one spontaneously fail, and could find no problems with
> the modem it had powered. The wall-wart had an open primary, so I
> disassembled it. Inside, I found the core's plastic bobbin was melted.
> While removing the primary windings, I found damage to the enamel wire
> that indicated that the wire had been wound too tightly when the core was
> manufactured. It appears that a few layers of the primary winding were
> shorted out from the factory. What seems to have happened, is that the
> remaining primary windings were over voltage, and eventually the heat that
> it produced damaged both the plastic bobbin and the wire's enamel
> insulation.
> USRobotics/3Com still would not send a replacement unit free of change,
> even tho this one was clearly factory defective. They want $15 plus
> shipping for these pieces of junk.
> I've been considering rewinding this particular transformer, just for
> practice (I haven't rebuilt one in awhile). I've not yet decided if it's
> worth possibly wasting some enamel wire on. I think I'd want to replace
> the plastic bobbin if I do decide to rewind this transformer.
> -Toth

If you want to rewind it just for nostalgia sake, fine. However, a bit
of rustling around in some of the thrift stores would likely turn up a
wall wart with the proper connector and a 9VAC output. I think I saw
one today when looking for a 6VDC one.
                                                 - don
Received on Sun Jan 20 2002 - 19:38:31 GMT

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:34:56 BST