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Author Topic: Fried computer motherboard. Potential grounding issue?  (Read 1737 times)

Tommy Peel

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Re: Fried computer motherboard. Potential grounding issue?
« Reply #20 on: August 19, 2020, 03:45:18 pm »

I would have thought that ungrounded circuits disappeared in the '60s, but it might be different where you are.

My own house (built in 1960) originally had no grounds.  I'm in the process of upgrading the service for a heat pump, and my electrician tells me it's "legal" to keep the 2-wire stuff, but any outlets have to be on a GFI.  That's probably what should be done first to keep people from being electrocuted.  Your jurisdiction may be different.  Others have made some educated guesses about the original fault.  An RPBG is a possibility, or there may actually have been a fault in a piece of equipment that put 120V on the chassis.

A non-contact voltage tester (NCVT) is the slickest way I've seen for testing for voltage where it shouldn't be (and where it should, although it doesn't give you a quantitative answer).  One of the best $25 investments I've ever made.

GTD

So swapping in some GFI outlets would at least provide us with some protection? And while I'm at it check for a RPBG? I've helped my Dad wire in outlets and switches several times, so that's not a big deal.
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Tim McCulloch

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Re: Fried computer motherboard. Potential grounding issue?
« Reply #21 on: August 19, 2020, 04:05:34 pm »

So swapping in some GFI outlets would at least provide us with some protection? And while I'm at it check for a RPBG? I've helped my Dad wire in outlets and switches several times, so that's not a big deal.

I'm not buying the electrician's response.  WHY was there a grounding problem?  The lack of an Equipment Grounding connection will not, by itself, cause the failure of a device.

I didn't go back and read the earlier posts but until someone can draw a circuit diagram that shows the likely fault condition I think the explanation is short sighted at best.  It's the "shotgun" approach of just updating things that are old or look suspicious without actually diagnosing the fault condition.

I'd be happy to be proven wrong, too.  But as my 8th grade algebra teacher said, "show me your work."
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Tommy Peel

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Re: Fried computer motherboard. Potential grounding issue?
« Reply #22 on: August 19, 2020, 05:36:08 pm »

I'm not buying the electrician's response.  WHY was there a grounding problem?  The lack of an Equipment Grounding connection will not, by itself, cause the failure of a device.

I didn't go back and read the earlier posts but until someone can draw a circuit diagram that shows the likely fault condition I think the explanation is short sighted at best.  It's the "shotgun" approach of just updating things that are old or look suspicious without actually diagnosing the fault condition.

I'd be happy to be proven wrong, too.  But as my 8th grade algebra teacher said, "show me your work."

Looking back I didn't word my response very well. The electrician didn't say that the missing ground was the problem; he wasn't sure what caused the "smoke release". I'm not sure exactly what he checked as I wasn't on-site when he was there(something came up with the day job and the church is an hour away); another church member let him in and I talked with him on the phone while he was there. He thought that the electrical looked "fine" for what it was; he did say that the panel was old(he thought 70s) and probably should be replaced as those old panels tend to not be that reliable.

Looking back at the old posts...

The missing measurements are:

PC H-Mixer N
PC H-Mixer H
PC H-Mixer G

etc.  Especially PC-Mixer Ground

You added a metallic connection between the two-that's when those relative voltages become a big deal-and why code is very picky about bonding things that might get interconnected.  If that 55 volts on the PC ground is a result of a capacitive connection rather than just a floating "phantom" voltage that could easily cause your issue.  That capacitor could be on another device plugged into the same "set" of outlets but missing a home run ground connection-maybe from a piece of conduit that is pulled apart if that was used as the equipment grounding conductor..

The easiest way to tell the difference between a "real" voltage and "phantom" is with a VOM-or low impedance DMM>

... I need to take my meter and do some additional measurements between the 2 outlets in question. I'll try and do that this weekend as well as following the guide to check for a RPBG.

Thanks everyone for their comments/suggestions!
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Stephen Swaffer

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Re: Fried computer motherboard. Potential grounding issue?
« Reply #23 on: August 20, 2020, 11:08:56 pm »

I tend to agree with Tim-as you clarified, it is unlikely the older panel did not cause the issue.  The only panel I have ever seen that was truly "ungrounded" was a fuse panel with both "hot" and "neutral" (probably technically both "hot") buses mounted on a piece of granite-everything exposed.  A lot of older panels are harder to isolate the neutral so you can properly use them as a sub-panel-but they usually have the neutral tied to the panel.

If the wiring is truly 2 wire (not 2 wire with an emt/conduit ground or equipment grounding conductor as is permitted by code), then any grounded outlets that show a good ground actually have a bootleg ground-and if one of the outlets is reversed polarity then you will have RPBG.  To me, the most definitive way to check that is to bring the two outlets next to each other and test voltages-then you will know for sure.
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Steve Swaffer

John Roberts {JR}

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Re: Fried computer motherboard. Potential grounding issue?
« Reply #24 on: August 21, 2020, 09:50:00 am »

So swapping in some GFI outlets would at least provide us with some protection? And while I'm at it check for a RPBG? I've helped my Dad wire in outlets and switches several times, so that's not a big deal.
That resembles my house lacking safety ground wiring.

I have since installed GFCI outlets in the handful of outlets near water (bathroom, kitchen, laundry room).

I have even added a DIY ground wire to the outlet in my laundry room and one in the kitchen by the sink.

+1 to using NCVT to identify stingers...

JR
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When in doubt do what's right.

Steve M Smith

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Re: Fried computer motherboard. Potential grounding issue?
« Reply #25 on: August 24, 2020, 03:11:48 am »

Any ideas on how to proceed?
Call an electrician.


Steve.
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Stephen Swaffer

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Re: Fried computer motherboard. Potential grounding issue?
« Reply #26 on: August 24, 2020, 12:27:10 pm »

Call an electrician.


Steve.

There are a lot of "electricians" I wouldn't trust on this one.
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Steve Swaffer

Tim McCulloch

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Re: Fried computer motherboard. Potential grounding issue?
« Reply #27 on: August 24, 2020, 01:08:49 pm »

Call an electrician.


Steve.

They did.  He proposed replacing a grandfathered "ungrounded" sub panel.  Without explaining what the problem was and how replacing this sub panel would correct the problem.

There are a lot of "electricians" I wouldn't trust on this one.

I'm with Swaffer.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

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Re: Fried computer motherboard. Potential grounding issue?
« Reply #27 on: August 24, 2020, 01:08:49 pm »


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