"Brian Gaff" wrote in message
...
Yes indeed. The only failure mode, assuming no lightning strikes or
similar. I have encountered is going open circuit due to the wire becoming
internally detached. Far more common are failure of the filters that often
are used as well. In these the capacitors go leaky and heat up making
usually magic very smelly smoke before the fuse pops.
A very dangerous device from many years ago, though I never realised it
till it failed was the pifco rechargeable torch. It had a two pin plug on
one end withed a cover and inside a 'lossless' dropper in the form of a
capacitor, then a tiny circuit that made around 7.5v which charged up some
nicads. Fine until one day the capacitor went down. put huge mains on the
semiconductor and the batteries and the whole room filled with smoke and
gunge started to leak from the torch dripping onto the carpet.
Luckily I way in at the time, but oh, the smell was in my nose for days.
the torch had partially melted.
No no fuse just a resistor across the pins to discharge any charge left
when you unplugged it.
I have also found that many shops are being duped into stocking stuff
that has CE on it but is rubbish. Take shaver adaptors with no fuse at
all, or wall warts with no fusible link, or ones secured together by
screws as short as those used for cassette tapes.
All very dangerous. Then there was the Eaton PSU from Maplin that dropped
all of 1 foot onto a floor and the two halves came apparently seemingly
being glued in two little places, exposing the mains terminals of the
transformer.
I could go on, but really I think worrying about an older adaptor is not
what you should be worrying about its the new stuff you need to watch for.
My old torch had lasted over 10 years before it died, but many of the
current wall warts seem to be good if they last three years.

Never had a wall wart fail and I've got heaps of
them and leave them plugged in all the time too.

"Archibald Tarquin Blenkinsopp" wrote in
message ...
On Sat, 2 Feb 2019 12:53:20 -0000, "Andrew Mawson"
wrote:

"Scott" wrote in message
...

I have a surge protection extension in the kitchen, used for TV,
decoder box and radio. It is very old. I read here recently that
these devices may present a fire risk. To my knowledge we have never
had any surges or spikes. Should I be ditching this device?

You will had had thousands of spikes. Every time your 'fridge compressor
starts you'll get a detectable spike. Whether they are of significant
magnitude is the question.

The MOVs in surge suppressors do have a finite capacity for absorbing
spike
energy, and at end of life can go s/c so always should have a fuse in
line,
but in an extension it presumably is via a fused plug

Andrew

The MOV's are VDR's, and as long as they are not called on to
dissipate more than their rating, they will work forever.

They are simply a Voltage dependent resistor. They have an infinite
lifespan if not overloaded.

The vertical oscillator/ output stage in old valve TV's used them on
the triode feed from the boost rail, specifically to stabilise the
Voltage. These never, ever failed.

There was one more in the frame stage, the thing would be across the
primary of the field output transformer. This handled spikes, lots of
them, 25 per second. They never failed either.

VDR's or MOV's do not simply fill up with spikes and fail in their
twilight years.

They are a Voltage dependent resistor and whereas your 10K is always
10K whether it has one or ten Volts across it, a VDR is what it say's,
"Voltage dependent".


AB



AB