[sdiy] power line transient protection

[Martin Czech]

Last year a friend lost his VCR, computer and TV due
to lightning. It wasn't even a direct hit, maybe a km
away. This is a frightening idea for us, because we
can't just pop into the next shop and replace our
destroyed diy synths.

Now this friend uses a line protection plug.
A quite expensive one and now I opened it and tryed
some reverse engineering...

Components: 
standard rf line filter
two neon bulbs
two varistors
one gas filled discharge tube
two ptc or ntc elements glued to the varistors
a fuse

I guess EUR 10 worth, the price was 45 EUR!

This is what I think now:
The varistors block neutral and phase to protective earth.
The gas tube blocks neutral and phase.
One neon lamp simply states, that the device is working
(has power on outlet). But the other seems to indicate
some fault, I think cracked varistors due to huge transient.
I guess such a varistor will get hot and therefore
turn on the ntc, and the red light neon will turn on.

(... oh Roxanne... turn on the red light for me ....)

I guess this is industry standard. Others recommend
a high power zener diode instead of varistors.

Do you have any other ideas?

m.c.

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