mains problem

Thread Starter


Joined Jun 27, 2008
not strictly electronics, but maybe someone can answer this one.
over the last few months a friend has brought me a number of mains items that have suffered catastrophic failure while he was using them in his cellar- two newish computers that have blown m/boards.or processor,and a newish media player unit which had blown the power supply unit.(a amall duall voltage unit) he actually recieved an electric shock from the metal on the player!
in 30 years of repairs and general tinkering i have never come accross.
anything like this.

any thoughts much appreciated


Joined Apr 20, 2004
I believe your power distribution has three line - power, common, and earth (we would call it ground). I would be concerned about the wiring. It sounds as if the earth is not connected or is miswired. It is there to protect from things like hot chassis. The power and common lines should carry all the current.

Does he or you have the means to verify proper wiring in the outlets? If it is incorrect, lethal shock hazard exists. In the line cords, brown is hot, blue is common and green/yellow is earth. A meter should read 220 VAC to earth and to common, but no voltage should exist between common and earth. The earth and AC common lines should tie together at the distribution panel.

Thread Starter


Joined Jun 27, 2008
thanks beenthere,i can certainly check his wireing.

however my mate who has no electrical knowledge, suspects that power surges could be responsible,very hard to check for this, i have advised him to use a surge protector socket,
the rest of the equipment in the house seems to be ok.
thanks again


ps just a note, in the uk, the designation live, neutral and earth is used .live and neutral are usually isolated from each other, back to the distribution transformer.

blocco a spirale

Joined Jun 18, 2008
Does the shocking media player have an earth connection? Have you checked the mains voltage? I once measured 253V at a house with a substation just outside the front door and that was early evening when demand would be near its peak. Some electrical equipment did not last long at this house.


Joined Oct 15, 2008
Suggest he has the wiring checked by a competent electrician before he kills himself or you. The cellar may be damp and quite unsuitable for indoor electrical fittings. ( I have some experience of old Yorkshire cellars!)
It would be advisable to fit MCB's /RCD's to the circuits to protect the equipment and also the users.