Case live at 50 VOLTS AC

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So while messing around with my computer I leaned over to take a look at the back and my cheek grazed the thumb screw on my case. I felt a light, constant zap! At first I thought "Ah, my skin is sensitive, maybe its a burr on the screw."
I just took a multimeter to it, 50 VOLTS AC!
Please help, I don't want to die. And by that I mean fry my components.
 
Solution
S
The basics is Ohm's law: voltage = current * resistance. In the above circuit, you have a voltage across each of the resistors. In theory, if you could measure the voltage across each of the resistors, it would add up to 120V. You measured the 50V just across the PC (the resistor, Rcase), i.e. just the voltage across 1 of the 3 resistors. In electrical engineering terms, this is a voltage divider. So, back to your original question. That's why you measured 50V and not 120V.

This is also why building codes changed from 2 prong sockets to 3 prong. It eliminates ground loops - appliances floating above a common ground. It's an electrical shock hazard.
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Scottray

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If your PC has been running OK, I think that you have grounding issue. Is the power supplies cord plugged into a grounded house electrical socket? If it's not, you need to be running your PC off of a grounded socket. If it is, than you have a grounding problem with the socket.
 
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Scottray

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Since you have a ground loop (not connected to true ground), you're measuring a differential voltage across the PC case. Here's a very simple circuit to explain it:

V120 ------ R1 ----- Rcase ----- R2 ----- GND

The PC case is "floating" above ground since R2 is not zero. The circuit is a voltage divider and you're measuring the 50V relative to each side of Rcase. Now when you plug your PC into a ground socket, this circuit changes. R1 and R2 become 0 and Rcase is open. You've removed the ground loop, i.e. the secondary path to true ground.
 
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Ahhhh I see now (still a noob when it comes to electronics/electrical). Since you're using "R", I suppose that's considered depicting a resistor. So I have a sort of resistive dropper? (trying to put into terms I know)
 
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Scottray

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Jul 14, 2016
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The basics is Ohm's law: voltage = current * resistance. In the above circuit, you have a voltage across each of the resistors. In theory, if you could measure the voltage across each of the resistors, it would add up to 120V. You measured the 50V just across the PC (the resistor, Rcase), i.e. just the voltage across 1 of the 3 resistors. In electrical engineering terms, this is a voltage divider. So, back to your original question. That's why you measured 50V and not 120V.

This is also why building codes changed from 2 prong sockets to 3 prong. It eliminates ground loops - appliances floating above a common ground. It's an electrical shock hazard.
 
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Solution
Flacker

Flacker

Commendable
Jun 27, 2016
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1,540
Well than that settles it, I gotta run some ground wire to this plug in my room. That'll stop my case from trying to fry me. Thanks so much for your help.
 
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