Two PCs GND to GND current !?

[vlad777]

Hi.

I have two PCs and if I want to connect one of them to stereo i have to
plug the jack from one to the other. I made it easy by using extension cord.
Few times i got not so small electric shock when I simultaneously touched both
PCs mass.

Today I actually measured the current and voltage between two masses using
rectifier + cap. I got 55V DC (when rectified) and 8mA short circuit current.
In my house I don't have earth so power cord's earth is not connected to anything.

I want to ask why do they put capacitors between hi voltage mass and
lo voltage mass inside the PSU.
I assume they responsible for this leak current or could it be somecind of malfunction?


I also tried to unplug the wall plug and reverse it, but same result.
I can connect two earth together but then that 8ma will be flowing somewhere.

Many thanks.

Edit:
When I press (audio)cord from PC1 against the PC2 (metal) housing i hear chirping/hissing sound
from that small spark so I conclude it is high frequency.

 

[MikeMl]

There are capacitors from each line to chassis. These capacitors create a voltage divider for AC, putting the chassis of each pc at a slightly different potential. If you are not willing to put "ground-loop isolators" (audio transformers) between the LINE OUT and the input of your stereo, then try connecting the pc chassis to your audio system chassis, and dont worry about the 8mA. Same pc to pc.

 

[vlad777]

Apart from those there are at least one direct hi to low mass cap. Why?

 

[vlad777]

Thanks a lot. I just killed my phones or phone line.
I use overvoltage protection extension cords with protection also for phone line.
I forgot that earth is connected to phone line trough varistors.
Strangely ADSL still works.

Edit:
Now when the telephone line is disconnected there is no leak current between two PCs.

Just a thought. These extension cords are pre ADSL so the varistors maybe have too low value.
What voltages are used in adsl?

This is what 8mA and some time do to a varistor:
**broken link removed**

Edit2:

Here is what happened: When I connected earths, leakage current got earthed trough phone line.
Mains unconnected earth is connected trough two varistors to both wires of the phone line.
Varistor to earthed phone line wire burned out, and then trough the other one leakage current killed my line.

I notified telephone company and I am hoping they don't find out what I did.

 

[Nigel Goodwin]

You shouldn't be using class I appliances without an earth connection - install yourself an earth connection - I can't believe anywhere in the 21st century would have such a completely unsafe mains connection.

 

[carmusic]

it is simple connect your 2 pc case together and find a earth ground somewhere, if you cant find, then tied the ground to neutral line, it is not the best way to do it but a least it is same potential as ground