Electric shock from my case. Is it the PSU?

lovelyhead

lovelyhead

lovelyhead

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I am having a problem where if I touch some of the screws on my metal computer case I am getting quite an uncomfortable electric shock. It isn't like a static shock but more like a continuous current. The screws that give me the shock tend to be the ones nearest the power supply.

My power supply is a Corsair RM650 fully modular unit which was bought brand new in November last year.

I have stripped the PC down to make sure the motherboard standoffs are correct, I have inspected all the cables for bare wire, I have checked for any pinched cables and I made sure to plug the PC directly into a wall socket rather than an extension lead. I also tried two separate wall sockets.

Still getting the shocks.

Is it likely to be a bad PSU or is there something else I should check?

This PSU replaced an old superflower that I had for close to 10 years without issue.

Thanks.
 
Can't imagine it is the explanation in this day and age but in the past I've seen PSUs where if you used longer screws than intended/standard when mounting it in the case it could make contact with things internally it shouldn't (seems kind of bizarre to me a PSU would have open back mounting holes). Also possible it is a PSU manufacturing fault.

Or you might have some really funky ground issue/leakage from another appliance.
 
BUDFORCE said:
Do you have a multimeter?

I be interested to start putting that across various points to see what is happening.
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I do but I don't really know how to use it beyond basic continuity tests.

I have went and ordered another power supply, an 850W Thermaltake Toughpower GF1, to swap out. The chances two power supplies, from two different brands both give me shocks must be miniscule so if I keep getting shocks after swapping it out then the problem must lie elsewhere.
 
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lovelyhead said:
I do but I don't really know how to use it beyond basic continuity tests.
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I'm no expert either, but literally just setting it to DC, putting one pin on the screw, one on ground, see what you are getting. Then for example one on the case of the PSU, one to ground etc etc start poking around, might give you an idea of where the leak is. You could go further by disconnecting certain things, testing again, might eliminate stuff.

Admittedly it's not particularly scientific.
 
Infact I'd be checking AC as well.

You are not going to feel 12v DC through your skin, which I think it the highest voltage on the DC output side of a power supply is going to provide unless there is some serious problem.

If it's giving you an uncomfortable shock it's going to be more than 12v.
 
Sounds like it's not earthed properly. Use your multimeter to check continuity between one of the black 0V wires coming out of the low-voltage side of the PSU and the earth pin of the mains plug. If that's ok, check between the earth pin and the metal case of the PC.
 
Two points on this.

1) It's almost certain there is a leak from the PSU, as mentioned if it was DC you should not feel it. This alone you have done the correct thing by changing PSU.

2) I would assume the PSU / Case is not grounded correctly. On modern cases they paint them, they also paint PSU screws, this stops / reduces the grounding. To solve this I scratch / file the paint from the PSU screw location, and use basic unpainted screws.
 
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JasonM said:
Two points on this.

1) It's almost certain there is a leak from the PSU, as mentioned if it was DC you should not feel it. This alone you have done the correct thing by changing PSU.

2) I would assume the PSU / Case is not grounded correctly. On modern cases they paint them, they also paint PSU screws, this stops / reduces the grounding. To solve this I scratch / file the paint from the PSU screw location, and use basic unpainted screws.
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The case is an inwin 303. I will take your advice and scratch some of the paint off of the case around the psu screw holes and use unpainted screws.
 
lovelyhead said:
The case is an inwin 303. I will take your advice and scratch some of the paint off of the case around the psu screw holes and use unpainted screws.
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This is what I did on mine, not very neat but it worked. Of course you do it on all 4 screws.


Also, if you have a side panel, you can do the same on those, this ensures side panels are grounded correctly.

I also ground HDD's !


In the past, all cases were bare metal, if you go back 25+ years. Over time they painted them so the computer including components are not grounding correctly.

One final thing! The case grounded or not, the PSU should still not be leaking electric, so your still correct to replace the PSU.
 
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JasonM said:
This is what I did on mine, not very neat but it worked. Of course you do it on all 4 screws.


Also, if you have a side panel, you can do the same on those, this ensures side panels are grounded correctly.

I also ground HDD's !


In the past, all cases were bare metal, if you go back 25+ years. Over time they painted them so the computer including components are not grounding correctly.
Click to expand...

Thanks that is very useful. It just so happens that the screws I have had a shock from were one of the screws holding the Power Supply in and also the painted black metal thumbscrew holding the back panel in place. This thumbscrew is very close to the PSU as well.

What made you decide that you wanted to scrape off the paint on your case? Were you getting shocks?
 
lovelyhead said:
What made you decide that you wanted to scrape off the paint on your case? Were you getting shocks?
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2 reasons.

1) This computer is a workstation / software dev machine, and correct grounding should make it more reliable. Grounding the HDD cases should make them less prone to interference.

2) I'm quite into audio, this machine has an Asus Essence STX II in it. By adding grounding can at least in theory only help the audio, for example the shield on the sound card is grounded to earth now.
 
JasonM said:
1) It's almost certain there is a leak from the PSU, as mentioned if it was DC you should not feel it. This alone you have done the correct thing by changing PSU.
Click to expand...
Most power supplies have a capacitor between the primary and secondary sides of the transformer, as this is an easy way to reduce the amount of electrical nosie they generate. This capacitor leaks a bit of current from the mains across to the low-voltage side. For equipment that isn't earthed, this can be felt as a tingling sensation or vibration when you touch metal parts. It sounds dodgy, but is actually perfectly safe.

I don't want to say for sure this is what lovelyhead is experiencing, but it's not necessarily indicative of anything other than an earth fault.
 
Mr Evil said:
Most power supplies have a capacitor between the primary and secondary sides of the transformer, as this is an easy way to reduce the amount of electrical nosie they generate. This capacitor leaks a bit of current from the mains across to the low-voltage side. For equipment that isn't earthed, this can be felt as a tingling sensation or vibration when you touch metal parts. It sounds dodgy, but is actually perfectly safe.

I don't want to say for sure this is what lovelyhead is experiencing, but it's not necessarily indicative of anything other than an earth fault.
Click to expand...

So do you think replacing the power supply is likely to resolve the problem? I never noticed this issue when using my old PSU in the same case.
 
It sound like the PC might not be getting a good earth. I'd start by trying a different power cable and also plugging into a different socket (ideally one on a different circuit).

Has the earthing of the electrical system been checked?
 
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K.C. Leblanc said:
It sound like the PC might not be getting a good earth. I'd start by trying a different power cable and also plugging into a different socket (ideally one on a different circuit).

Has the earthing of the electrical system been checked?
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I have changed the power cable but it didn't make a difference.

We had an EVSE fitted last year so I would assume the earthing situation had to have been decent enough for that.

I just remembered that I had a very similar situation occur many years ago when I still lived with my Mum at her house. I bought a Yamaha receiver and got the exact same electric shock from that. I returned that reciever and got the same model as a replacement and it worked perfectly with no electric shocks whilst still using the same electrical socket. So I know through experience that it can happen through faulty equipment.
 
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Mr Evil said:
Most power supplies have a capacitor between the primary and secondary sides of the transformer, as this is an easy way to reduce the amount of electrical nosie they generate. This capacitor leaks a bit of current from the mains across to the low-voltage side. For equipment that isn't earthed, this can be felt as a tingling sensation or vibration when you touch metal parts. It sounds dodgy, but is actually perfectly safe.

I don't want to say for sure this is what lovelyhead is experiencing, but it's not necessarily indicative of anything other than an earth fault.
Click to expand...

Yes your correct, it might not be dangerous and sorting the earth it might be ok.

Just one thing, I've had PC's since the 80286, and never had a shock from a PC case. But still agree it might not be dangerous.
 
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