On Fri, 18 Oct 2013 12:21:09 +1100 "Phil Allison"
wrote in Message id: :


"Arfa Daily"

So, bottom line, by all means try a replacement fuse first. You may be
lucky and get away with it. But be prepared for your new fuse to fail
immediately ... :-\

** Fuses cost money and I don't like to see them blow at switch on.

So my standard practice is to fit a new fuse and then connect the AC lead to
a Variac via a current meter ( true rms) and slowly wind up the voltage.
With a SMPS, the current reading should be small until it suddenly strikes
and runs at some voltage between 80V and 160V as shown on the Variac's dial.

If a current near to the fuse's rating appears at a low setting on the
Variac, then its game over.

In cases where the PCB has to be exposed to get at the fuse, visual
inspection for damage is the first step and then an old fashioned moving
coil multimeter on the low ohms range to check PSU diodes and the switching
transistor for shorts.

BTW:

Guitar amps regularly arrive with either no fuse or a glaringly wrong size
or type fuse - ie fast fuses in the AC.

However, the ones I really hate arrive with NO fuse cap in the holder.

Grrrrrr.........

Better yet if you can find one cheap, a Sencore PR570.
http://www.ebay.com/sch/Electrical-T...R40&_nkw=PR570
It has the capability to automatically trip and shut down it's AC output
if the current exceeds whatever setting you dial in. It doubles as an
isolation transformer and variable AC power supply as well. Got one of
these for $150 a year ago on Ebay, I can't count how many times I've used
it.