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Getting small electrical shocks from the rig

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eagle1109

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Hello,

I recently started to get a little shock strikes from touching the rig for moving it or just to mount something.

So I thought that this is not normal and there's something leaking current.

I started diagnosing the source of the problem, so I disconnected the parts and connect the PSU and test if the leakage is still present, I eventually disconnected all the parts and the shock is still found on the motherboard ground with setting on the ceramic floor bare feet.


So now it's either the motherboard or the PSU which is causing the problem. Both of these parts have a history of having a problem with.

1. The PSU, this unit actually broke before months and it was the 12V rail output power MOSFET, so I replaced the MOSFETs and it worked again like a charm. But in this current situation, I think there could be other parts which might be broken and I'm not aware of.

It could be small parts which are not necessary for the operation of the unit, but maybe if one of them is broken then they might cause a problem, and this one I think I can't fix if it's true because it would be difficult to test.

>>> a quick update, I just went to the setup to test something, everything is powered OFF, and the switch of the PSU is OFF too. I touched the motherboard and there was a strike! So I disconnected the power cable of the PSU and the charge just gone, THEN, when I tried to connect the power cable and my HAND was on the PSU case I got a strike!

I think it's the PSU.


2. The motherboard, this unit took a hit during airflight shipping process and the GPU wasn't screwed, so it was rolling inside the rig all the time, until I received it and of course the GPU was broken, didn't work.

After that, one of the fans port doesn't boot right away when the I switch on the motherboard, it delays a little and then run.
 

KlausST

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Hi,

Please take photos that we can see what you are talking about.

* I assume it is ESD what you are talking. This is not a problem of the PSU but the problem of your shoes and charge that is built when you move on the floor or move on the seat.

* but it may be the PSU. I expect it to be earthed somehow. But without information we can just guess.

Klaus
 

eagle1109

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I disconnected everything.

Put the motherboard on a box, the PSU on the ceramic ground, switched on the power, then I touched the grounded motherboard screws and I get the same strike. So I knew it's either the motherboard or the PSU.

 

FvM

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PC PSU are designed to be operated with protective earth connection. Can it be that the PE connection is discontinued somewhere between the PSU and the switchboard, e.g. by using a two terminal power socket or two wire extension cable?
 

KlausST

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Hi,

Now I fear that there´s something wrong with your EARTH_GND.
Usually the PC case is connected to EARTH_GND via the PSU. This seems not to be that case with your PC.

Be careful. There seems something to be wrong.
Thus avoid to touch anything conductive with your bare hands. Not the water pipe, not the EARTH_GND, not the PSU case, not the computer case...


Do you have a 100k Ohms resistor and a DVM for AC voltage measurement?

If yes:
* Take the DVM
* select AC volt, range up to your mains voltage.
* use two wires to connect the 100k resistor to the AC inputs of your DVM
* use a second pair of wires (1 and 2) and connect them to the DVM, too. (in parallel to the resistor, too)
* connect the other side of wire (1) to any water pipe or heating pipe around. (this should be our neutral 0V reference)
* connect the other side of wire (2) to the EARTH_GND of the power outlet (without PSU connected)

It should show less than 5V. Usually less than 0.5V. (EARTH_GND w.r.t. water pipe)


****

If so, then disconnect wire (2) from the outlet and connect it to the PSU_case. Somewhere with bare metal.
Now connect the PSU to the power outlet. Switched OFF.

It should again show less than 5V. (PSU_case w.r.t. water pipe)

****

If good, then switch the power supply ON.

It should still show less than 5V. (PSU_case w.r.t. water pipe)

****

If good, then disconect wire (2) from PSU_case and connect it to system_GND (black PSU output wires?)

It should still show less than 5V. (System_GND w.r.t. water pipe)

****

If good, then disconect wire (1) from water_pipe and connect it to EARTH_GND

It should still show less than 5V. (System_GND w.r.t. EARTH_GND)


Klaus
 

dick_freebird

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I'd go after the ground bond. You could set up a 'scope
with a known good ground reference and poke around
at the points along the path from plug to chassis to board
ground plane and see where the amplitude jumps up.
 

eagle1109

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Hi,

Sorry for the late late response :)

I gave up this issue and left the rig as is, still there is some charge accumulation every time but I don't want to go back to the psu and mess with it and then I broke it by a mistake.

If the rig is working then I'm not so much wondering about this issue. I really want to solve it, but I tried many times to inspect the problem.

I disconnected everything from the motherboard and there's something maybe wrong in the motherboard but I can't fix it.

It arises as soon as I connect something to the motherboard.
 

joystik

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Hi.

The problem is most likely that the chassis has lost its connection to ground.
Check the Ground in the power outlet first. If that proves ok then connect the power cable to the power supply, but not to the power outlet. Measure continuity between the PC chassis and the Ground pin on the power cable. Normal readings for this is close to 0 ohms. If its not, keep testing until you find where the continuity is broken.

If the power outlet ground is faulty, you will need an electrician to diagnose and repair it, unless you want to do that yourself. However, best bet is to have it done.

Good luck.
 

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