Shocking & Tickling Computer SMPS...

[zmint]

My HP Pavilion Desktop gives a little shock (funny-bone tickling sensation) when touched especially if one is bare feet (without rubber shoes or slippers). The shock is not so shocking as of 220V AC but still, make its presence felt. So I thought of eliminating the cause as my budding kid may touch it inquisitively.

Deciding to Starting with the SMPS, I opened this branded SMPS & here is what I noticed, which I didn’t understand but could be a cause of the problem :

The three pin socket (obviously for phase, neutral and earth) for 220 AC-IN, had a strange connection. The Earth pin which is wired to the SMPS’s metallic case is also connected to the other two pins (phase & neutral) via two separate ceramic looking, blue colored capacitors marked CS 417 K.

1) Why would that do that ? Obviously the experts know better ....
2) Could it be possible that the two Caps are misbehaving and are not doing what they are supposed to do and started discharging some current to the earth. ?
3) Can I safely discontent the two Caps from Earth ?
4) I well understand that, this problem could not have arisen if had a proper earthing in my house wiring. But the wiring is a bit old being in a remote area with no separate third wire coming to take that shocking cause back under the ground.
5) Or may be, I can make a simple earthing for my PC by drilling a nail in the cemented wall nearby and connect the third earthing wire to it.
6) Lastly, I also noticed that the simple householder pen type tester used to check phase and
neutral also glows brightly when touched to the SMPS, clearing indicating that something fishy is going on inside.

What option do I have now ?
Whatever the solution you suggest .......


Thanks.

 

[Diver300]

Sounds like a faulty earth connection. It might not be a fault in the PC but it could be in the feed to it.

If there is a good earth, there should be no voltage on the case. Whatever leakage current leaves the SMPS should be taken to earth and there should be no voltage on the case.

 

[MikeMl]

Just to amplify what Diver said: Likely the fault is in your house wiring; missing ground connection between ground pin and earth ground.

 

[zmint]

Thanks MikeMl & Diver300 for the effort but please read point 4 and 5 in my original post. I already declared that my antique house doesn't have a proper earthing facility.

 

[mvs sarma]

with budding kids with over enthusiasm at home, better and safer not to open the smps like power equipment.

 

[Reloadron]

4) I well understand that, this problem could not have arisen if had a proper earthing in my house wiring. But the wiring is a bit old being in a remote area with no separate third wire coming to take that shocking cause back under the ground.
5) Or may be, I can make a simple earthing for my PC by drilling a nail in the cemented wall nearby and connect the third earthing wire to it.

Adequate earth ground should be acheived by driving a good, copper plated, earthing rod into the ground. A nail driven into cement will not provide adequate ground.

Something else, I am not familiar with the power mains in your location but here in the US the neutral line is tied back to ground at the circuit breaker panel (mains entry point). The outlets are what we call polarized with hot and neutral. If your distribution is similar is there any way that the hot and neutral are reversed on your socket you are plugged into? This led me to wonder:

6) Lastly, I also noticed that the simple householder pen type tester used to check phase and
neutral also glows brightly when touched to the SMPS, clearing indicating that something fishy is going on inside.

Ron

 

[MikeMl]

Thanks MikeMl & Diver300 for the effort but please read point 4 and 5 in my original post. I already declared that my antique house doesn't have a proper earthing facility.

So fix the house and leave the computer alone...

 

[zmint]

nobody talking about the two ceramic looking, blue colored capacitors marked CS 417 K. Can I safely disconnect tham ?

 

[zmint]

with budding kids with over enthusiasm at home, better and safer not to open the smps like power equipment.

Sharma Sahib, Leave the safty of the kids to me and suggest something more fruitfull towards my current leaking problem...

 

[Diver300]

You probably could disconnect them.

What we are worried about is that if something else fails, like you get water or rodents in the PC, or a loose wire or something, an unearthed case could kill you. The same would apply to many appliances in your house.

If the PC makers could get away with a 2 core lead, they would.

I can't see what is so difficult about an earth rod. I have one for this house. They are standard electrical components. You just hammer it into the ground and connect a wire from that to the earth terminal of the distribution board.

 

[mvs sarma]

perhaps you are using a 2 wire extended strip board to connect the PC to power supply;
instead, use a 3 wire power board . ensure that third wire in you home is having ground connection.
then the PC would not give any shock.!!! All the best.

 

[zmint]

ensure that third wire in you home is having ground connection.

I very well know that the third wire is not having a ground connection.
How can I make myself (DIY) a good or well to do ground connection.
What type of rod ?
How long ?
How deep ?
Any thing else ?


Thanks.

 

[Reloadron]

I very well know that the third wire is not having a ground connection.
How can I make myself (DIY) a good or well to do ground connection.
What type of rod ?
How long ?
How deep ?
Any thing else ?


Thanks.

I can't speak for the other side of the pond but here in the US the method is an 8 foot rod driven into the ground. The rod is copper plated. The use of a copper cold water pipe was also used at one time. I still wonder if your mains has a neutral and hot if they could be reversed?

Here, grounding rods are available from any home improvement store.

Ron

 

[Diver300]

The type of rod you need depends on what the ground is. Dry sand or rock make it very difficult.

Here in England it is the ground is usually soil or clay. Deeper than 0.5 m it is always wet, so an earthing rod 1m long, driven straight down until the top is level with the surface is normal.

Earth Rod - Screwfix.com, Where the Trade Buys

That is a steel rod which is copper plated, 1220 mm long and 9.5 mm diameter.

I assume that you have a ground connection on the distribution board for the electricity in the house. You would hammer a rod like that into the ground, and connect it to the ground on the distribution board with 6 mm² or larger copper wire.

Do not disconnect any other earth connections.

You could also find out what is normally done where you live. You haven't said where you live.

 

[ChrisP]

nobody talking about the two ceramic looking, blue colored capacitors marked CS 417 K. Can I safely disconnect tham ?

Those devices are most likely not capacitors -- instead, they are likely to be MOV's (metal-oxide varistors) used as a form of basic surge protection for the SMPS. Take a look at the datasheets associated with these products -- the diameter of an MOV is a first-step key in identifying it...

 

[InventionUnlimited]

I agree with chrisP, i also think they are for clamping the input in a surge situation. Why would you want to disconnect them? They obviously work or they would not be in the power supply. A ground rod works wonders, I just added one in my workshop, its the only way I could get my plasma CNC working properly.

 

[mvs sarma]

we should not modify the SMPS, just because we don't have ground connection to our homes.
I used to study the Rural Electrification Authority(REA) manuals on grounding etc .
there is a standard of providing ground bars for any electrical installation. please check and restore any broken wires connecting ground bar to the electrical wiring in you home.