On Fri, 02 Feb 2018 18:00:36 +0000, Johnny B Good wrote:

On Fri, 02 Feb 2018 15:29:34 +0000, ss wrote:

====snip====

Update:
So fuse arrived today, soldered in to the charger, switched on and POP!

Just as I expected and tried to advise you of this most likely outcome.
Once that safety fuse has blown, you can guarantee that the cause was an
HT switching transistor[1] going short circuit for one reason or another
which may well involve a fault in any of the components in the driving
and control circuitry. Just blindly replacing a blown HT switching
transistor is far from guaranteeing a successful repair.

That will be for the bin then as now beyond my understanding of
electronics.

And mine, too (and I'm far more knowledgeable of SMPSU basics than you
[2]).

At least it never exploded this time.

Probably just a matter of "dumb luck". :-)


Ok now waiting on replacement fuse & holder for the other charger,
fingers crossed.

From what I can recall, that looks a much better bet.

Oops! Forgot to add the [notes]

[1] or, if you're very lucky, a shorted bridge rectifier diode.

[2] I may know the basics but most of the drive and control circuitry in
modern day SMPSUs will be integrated into a custom controller chip or two
which would need to be identified and a data sheet tracked down before
one can even begin to think about attempting to diagnose and repair such
a unit. Unless it's truly impossible to substitute the failed SMPSU with
another off-the-shelf unit, it's normally much cheaper to replace rather
than repair an existing one.

--
Johnny B Good