At first, I must say that my question may be judged as out of topic. If so, I would obliged if advised to which site may I consult.

I have an old VGA monitor which I connected with my laptop. It works fine, but I realized that a current leakage occurs. The cover of the laptop is made by some kind of aluminum, so I touched it and felt some small amount of current passing through my fingers.

I was told that the monitor has a faulty ground, but otherwise it should work fine.

I would like to ask if the laptop or any other device connected to it, is at risk, due to the faulty monitor.

Any thought would be appreciated.

  • \$\begingroup\$ If you are included in 'any other device' I'd say yes. And also if you are not. Monitors are quite cheap, I wouldn't play around with a faulty one. \$\endgroup\$ – Vladimir Cravero Apr 21 '16 at 12:15

Of course there is a risk. It sounds like you have "lost" the internal earth connection entirely. This will likely mean that any internally bonded metal parts will acquire a voltage that is about 50% of the line voltage.

The 50% figure comes from the live and neutral capacitors used to reduce conducted emissions. Those capacitors will also bond to local earth and with that local earth being disconnected from proper earth they will form a potential divider raising all internally earthed parts to 50% of your supply voltage.

That is why you felt a tingle in your fingers. There could be a serious safety issue here but without knowing the types of capacitors on live and neutral you have to assume safety is being compromised.

So, will it damage other apparatus connected to it. Yes it could but without knowing how well the "other apparatus" is at protecting itself it's impossible to say.


There was a story in the South China Morning Post just yesterday that illustrates a possible hazard.

Chinese man, 18, dies after unhooking mobile phone cable from internet cafe computer

“He cried out when he first tried to disconnect the cable and then he touched the device again while his feet came into contact with a steel pipe below the desk,” the brother was quoted as saying.

The teenager foamed at the mouth and his body became frozen before losing consciousness, his brother told the newspaper

Most likely this was a similar ground fault, just one that passed more current. The unfortunate young man apparently completed a circuit between the USB plug and a well grounded pipe.


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