How do three fuses fail simultaneously ? I have just repaired a small
external switcher from an LCD TV for one of my trade customers. 12V @ 5A -
you know the sort of thing. It had two 2.5A Wickman fuses just south of the
line input connector, so that's one each in the live and neutral feeds. It
also had a 3A plugtop fuse fitted, this being in the UK. So that's three
fuses all effectively in series. Two of them directly so, and one in the
other (return) side of the input circuit. All three were open, and the cause
of this appeared to be that the main filter cap was bulged and open,
although I'm not entirely sure why this should have led to excess input
current, as I have seen open main filter caps many times, and fuse failure
from this alone, is not the usual symptom.

However, vagaries of switcher behaviour aside, how can three fuses -
especially considering that one of them is a higher rated plugtop fuse, not
known for their accuracy - that are all in series, all be open ? Clearly,
as soon as one fails, in theory at least, all current through the other two
is interupted ...

As soon as the cap and three fuses were replaced, operation of the supply
was normal, and it powered the TV without issue. Thoughts anyone ?

Arfa