ESD Issue - Long winded

[lancew70]

I'm trying to understand why ESD on the external portion of computer case fried my motherboard on two different occasions over a 4 month period.

In each event, I was reaching to push the eject button on my DVD drive. The ESD caused the computer to power off and in each of the two occasions; the motherboard underwent a catastrophic failure.

Had I been inside the case when this occurred, well, this would be a no-brainer as they say.

The only time I've heard of ESD on the external portion of the case causing a catastrophic failure was when the computer was not properly grounded.

After each of the two ESD events, I checked to ensure that my 3-prong outlet was properly grounded. The computer is connected to a Belkin 1100VA UPS which connects to 3-prong receptacle. The earth ground was checked with an inexpensive outlet tester (the kind that shows “open Ground”/Open Neutral/Open Hot/Hot/Grd Reverse/Hot/Neu Reverse/Correct) and a digital multimeter. All indications were that a good ground existed.

I’ve even had an electrician come to my house and check the wiring/receptacle for proper installation/ground.

The mobo was inspected and the stand-offs were all verified to be in correct (none where they did not belong). The mobo was not making improper contact with the case as best as I could tell.

The power supply (a new PC Power & Cooling 610) was tested and found to be in good working order.

The computer (3-prong cord) was plugged into a UPS (no indication of a Site Wiring Fault) and the UPS is plugged into a grounded 3-prong receptacle.

It's possible but it just does not seem credible that the spark would have to jump from your finger through the non-conductive plastic of the button and enter a live circuit without encountering any grounded part of the drive's chassis or computer case first.

For the DVD Drive, the electrical grounding is handled through the power cable grounds. By removing the Bezel on the front of the DVD Drive it looks like the switch is supported by a metal bracket that is soldered to the circuit board. On the front surface of the switch there is a small metal shield with an opening just large enough for the activator button to protrude through. On the chance that a static charge winds its way around the outer button through the bezel it will be picked up by this shield and routed to the DVD's circuit ground and then to the DVD case.

I did, after the second ESD event, find a bare exposed wire on the Ribbon cable (pin 39, LED indicator) that connects to the DVD and to the Mobo that was most likely touching the metal case of the DVD drive. I was thinking at first that this bare ribbon cable wire touching on the metal DVD case might be the culprit.

However, a couple of PE-EEs that have reviewed these two events don't think that the Ribbon Cable is a contributor to the ESD causing a catastrophic failure of the mobo (twice). They just don't feel that even a short in that ribbon cable could lead to ESD given the low voltages in those conductors.

I've replaced the power supply, DVD Drive (& the obviously bad ribbon cable), case fans and taped over all unused Molex connectors.

I've placed an electrically conductive mat in front of my desk and computer with grounding straps to the grounded receptacle and a second grounding cord that has a wrist strap that is on top of my desk that I can touch before touching my computer.

The conclusion by the professionals that have reviewed my situation is that they feel that this occurred because something is just not properly grounded.

I believe them too, but I just can't find anything other than the bad ribbon cable that seems to be out of order.


I did read about another person who recently had the same problem when he touched the eject button on this DVD Drive which caused he computer to power off. However, he was able to reboot and all seems to be fine for now (he might have some unknown latent issues though). He could not find a grounding issue either.

I trust and believe the professionals that have provided their opinions on this issue. However, I just can’t seem to find convincing proof as to the cause. I’m most likely beating a dead horse in the ground but I have always been a big believer in Peer Reviews as a good method for reviewing problems/solutions.

Has anyone else seen/heard of this type event?

Could it have been the DVD Drive (It showed to be grounded when testing with multimeter?
Could it have been the ESD coupled with the Ribbon Cable hitting the metal DVD Drive?
Could it be something in the construction of my case? (Tests don’t indicate grounding issues.
Could I have just plugged a cable in incorrectly on both occasions that fried the mobo?
I’m even going to replace my case just out of fear/ignoranc

Something was not grounded, but what?

At this point it may be to all speculation, but II would appreciate any further comments/thoughts on this situation. I'm just not convinced I've found a solution to my problem.

p.s., I do admit to being very anal retentive

Thank you

 

[agent420]

I don't see how you can even prove this was esd related. Coincidence? Perhaps. But it could be anything.

The conclusion by the professionals that have reviewed my situation is that they feel that this occurred because something is just not properly
grounded.

If you have access to professionals, what do you expect to gain here?

I doubt it's esd, unless you're hair is always standing on end. That concerened? Wear a grounding wrist strap. But more than anything else I think you have either a poor connection somehwere or something is loose. I just don't buy the whole esd killed my pc twice in 4 months. The outside of a pc case is inherently grounded, and even if it were not, would still protect the internal components just like a car protects you in a lightning storm.

You are looking for the most difficult explanation imo.

 

[MjrStryker]

I'd have to agree. I doubt it's ESD per sae. You mentioned a bare wire on the ribbon cable could've been touching the chassis. This doesn't seem very likely to be the cause of any concern since an LED Indicator wire should be in the low state at least at some point. By touching the case it's simply forcing it to the low state.

***Edit: On second thought, it is possible that without the current limiting resistor and led in the loop, sending that wire to ground could feasibly cause a short when the led indicator was supposed to be triggered. This does somewhat resemble the behavior you described.

I'd look more into your DVD drive seeing as how the Eject button seemed to trigger both failures. The only things in the loop that include the eject button circuit are your case, mobo, psu, and dvd-drive. You've determined that the psu is fine and the case properly grounded, so let's rule those out for now. The remaining items are the mobo and dvd-drive. You also know that the fault occured twice with different mobos. This means that the dvd-drive is really the only constant factor here. You also have information that suggests someone else had a similar experience with the triggering of the eject button causing a fault.

At this point, I'd suggest looking into the dvd-drive being the culprit and try replacing it before buying an expensive new case. dvd-burners are something like $30.00 on the egg for a nice OEM model with 12x dvd-ram capability.

 

[agent420]

btw, my pc has no external case, is mounted on static friendly acrylic, and I have to walk on carpeting then touch bare components to load and unload cd's...

yet I've never had an esd issue... (or have I ?... you can never really know for sure )

(fwiw I've cleaned up the loose cables since these pics were taken, but that is purely aesthetic)

 

[lancew70]

Thanks for the informative responses agent420 and MjrStryker.

agent420, I find your comment "I doubt it's esd" very interesting because another very experienced EE said essentially the same thing:

When asked "what do you believe is causing our static electricity discharge with the eject button on our optical drives?", his response was:

"I'm not at all sure that it exists, but if it does, the spark would have to jump from your finger through the non-conductive plastic of the button and enter a live circuit without encountering any grounded part of the drive's chassis or computer case first, as soon as it encountered a grounded part it would be harmlessly dissipated. That is pretty hard to swallow!"

I'm not in any way disputing his professional opinion I'm just trying to find the source of the problem (other than me ) However, after each event I've had an electrician (different ones) check my grounding from computer to oulet and they can find no grounding issues.

After both of my "ESD"? events I've checked all connections in the case and cannot find any suspicious items (other than after the second event I did find the exposed wire on the DVD Ribbon cable. Again though, most of the Pros don't think it's the culprit.


MjrStryker... Regarding your comment "***Edit: On second thought, it is possible that without the current limiting resistor and led in the loop, sending that wire to ground could feasibly cause a short when the led indicator was supposed to be triggered. This does somewhat resemble the behavior you described"

I would like this to be the problem since I cannot find anything else but I've just not had any good professional confirmation of this. If it was the cable, I could at least rest comfortably that I had found the problem.

As to agent420's statement "If you have access to professionals, what do you expect to gain here?" You make a good point and I may never be able to know the cause but I'm sure it's just me being too darn anal retentive. As I stated above, I'm a big believer in Peer Reviews and I think it's interesting to hear other's opinions, especially if they have had a similar issue.

What I do know is that on 2 occasions when reaching to push the Eject button on my DVD Drive I felt what seemed to me was a static shock and the PC shutdown and required replacement of the mobo. A Doctor in Arizona responded to my post stating that he had the exact same thing happen, only his PC rebooted and is still running "OK" (I'm sure he and I both have some "walking wounded" that we'll experience down the road.

Perhaps the problem was with the DVD Drive. I'm still chasing that one with the manufacturer, but they are a bit reluctant to get involved since they may think I just want to blame it on them and try to make them replace the drive and my mobos. That's not the case, but I can understand their reluctance. However, I don't believe it is the DVD Drive...If it was more than just two people would be posting on this type of event IMO.

After seeing the posts on Hardforum regarding ESD I thought I would post it here and see what infomration I might pickup. I don't mean to be a PITA

Thank you very much for you informative comments

 

[agent420]

As to agent420's statement "If you have access to professionals, what do you expect to gain here?" You make a good point and I may never be able to know the cause but I'm sure it's just me being too darn anal retentive. As I stated above, I'm a big believer in Peer Reviews and I think it's interesting to hear other's opinions, especially if they have had a similar issue.

I'm glad you took it that way, because it was not my intent to be crass My point was simply that 'professional' opinions probably carry more weight than the subjective comments or guesses you're likely to encounter here many times, especially for such a technical subject. No offense - this is a great place (that's why I swing by). But this is almost more the realm of someplace like ElectroTech Online... and even then I think you'd get avrying opinions...

 

[lancew70]

Thanks agent420. I understand.

Thanks again for your candid opinions

 

[Mohonri]

I'd also agree with the comments that something beyond ESD is at fault here. I'm also an EE (though not a PE, as the certification wouldn't do much for me at this point), and I would agree that the DVD drive is the most likely culprit. As MjrStryker said, the DVD drive is the common component here. And as much as I respect the work you've done to try to nail down the cause, I'm not convinced that the PSU isn't at fault. Particularly if it's an intermittent problem, the PSU could seem fine when tested, but still exhibit unusual behavior at other times.

The biggest problem here is that it's not practical to go through the usual scientific methods of determining the cause, because 1) it's very intermittent, and 2) it's expensive to repeat .

Out of curiosity, have you done any modding on this case that involved cutting metal? If so, there's a possibility that some metal shaving or dust got someplace it shouldn't.

One more suggestion: if you haven't already, see what else is connected to the computer that connects electrically somewhere else. I wonder if something isn't happening at, say, the other end of a network cable and being transmitted back to this computer.

 

[MjrStryker]

Question: Were both motherboards the same model and revision? Perhaps there is a possible inherent defect in these boards that the consumers should be forewarned about?

 

[lancew70]

Mohonri/MjrStryker: Thanks for the very interesting comments.

As to the PS, the only test that I ran on it was the one suggested by the manufacturer (PC Power & Cooling). The instructions they provided were to:

With a meter see if you have continuity between the black DC output wires and the earth ground of an outlet. Try plugging it directly into the wall without the UPS.

I have used a Digital Multimeter to test the continuity of each of the Black DC output wires. There are 10 black wires that are connected to 8 Pins and I tested each of the 8 pins. Each show to have continuity (0.7 ohms read for each of the Black DC Output wires). After providing these results back to the MFGR. they stated that the PS should be "OK".

If the PS is experiencing an intermittent problem, is there any reasonable/simple test that I might be able to conduct to detect a potential problem?

I have not done any any modding of the case (I'm an old nerd ) The case is an Antec Solo and during my inspection of the case I'm not able to detect any issues with the chassis.

Regarding

what else is connected to the computer that connects electrically somewhere else

The following items are connected to the computer:
- Printer (Inkjet) Connected to UPS (USB connector to computer)
- NEC MultiSync 90GX LCD Monitor
- Altec Speakers connected to Subwolfer (the Subwolfer has 2-prong cord connected to UPS)...humm, it's about 10 yrs old now. I'll check the cables.
- Ethernet Cat-5 routed through UPS Ethernet Connector.
- Cable Modem power is connected directly to 3-prong wall outlet (same one as UPS is connected to)
- Linksys Router power is connected to UPS
- Logitech Key Board

Is there a good way that I can use to check for problems on these devices?


MjrStryker... The mobo is ASUS M2N-E (both that failed) and the one currently in the computer is the same ... I've not found any posts indicating a problem with this board other than issues that were corrected through BIOS updates). I can't be sure but I do think each of the mobos were/are the same revision.

Regarding the DVD Drive, I've put it in an old PC my son has (separate residence) and he is monitoring weekly to see if any similar problems occur. Can you suggests any test to check the DVD for problems? It seems to work fine playing/burning DVDs. Could there be a problem with the ground pins on the power connector? After the first mobo failure I checked the grounding with a digital multimeter and as best I could tell it was grounded.

Mohonri and MjrStryker...These are interesting comments and you've given me some new things to think about and investigate. A great big thanks!

Thanks for any further comments.

 

[Mohonri]

0.7 Ohms seems higher than it should be for ground wires--power supply wires are typically 18 AWG, which should give you lots less than 0.7 Ohms.

The problem with intermittent electrical problems is that there's no effective way to make sure you see the event again, because it's intermittent. By the same token, it's impossible to prove that one or another component is at fault.

 

[lancew70]

0.7 Ohms seems higher than it should be for ground wires--power supply wires are typically 18 AWG, which should give you lots less than 0.7 Ohms.

The problem with intermittent electrical problems is that there's no effective way to make sure you see the event again, because it's intermittent. By the same token, it's impossible to prove that one or another component is at fault.

Thanks Mohonri..

I just reran the continuity test on the PS but I did not plug it into wall receptacle and it read 0.3 ohms on 5 of the black DC output wires and 0.4 ohms or the other 3 black DC output wires. I can confirm that the wires are indeed 18 AWG.

I put one end of the probe into each black wire pin of the PS mobo connector (ATX Connector) and the other I touched to the neutral prong on the PS outlet. Is this correct in your opinion or does it need to be connected to the wall receptical?

 

[Mohonri]

Thanks Mohonri..

I just reran the continuity test on the PS but I did not plug it into wall receptacle and it read 0.3 ohms on 5 of the black DC output wires and 0.4 ohms or the other 3 black DC output wires. I can confirm that the wires are indeed 18 AWG.

I put one end of the probe into each black wire pin of the PS mobo connector (ATX Connector) and the other I touched to the neutral prong on the PS outlet. Is this correct in your opinion or does it need to be connected to the wall receptical?

Ah, I see now. I was thinking the 0.7 Ohms was between wires on the same GND bus inside the PSU. Even so, the GND on the AC side of the PSU is always connected to the GND on the DC side of the PSU, thanks to everything being grounded through the case, so I'm still a bit mystified why you're even getting 0.3 Ohms. My guess is that your DMM might not do so well at resistances that low, but I could be wrong.

 

[lancew70]

Ah, I see now. I was thinking the 0.7 Ohms was between wires on the same GND bus inside the PSU. Even so, the GND on the AC side of the PSU is always connected to the GND on the DC side of the PSU, thanks to everything being grounded through the case, so I'm still a bit mystified why you're even getting 0.3 Ohms. My guess is that your DMM might not do so well at resistances that low, but I could be wrong.

My DMM is not an expensive one (`$25.00) and it's a INNOVA 3320 made by IEQUUS I think.

I was on the Electro Tech forum last night and one responder (don't know if he's EE or what), was of the opinion that my problem was that the DVD Drive Case was not grounded to the PC chassis. When I noted back to him that "electrical grounding is handled through the power cable grounds" his response was interesting:

The system power ground is part of a closed loop for power regulation it's not meant to be a target for current spikes to discharge through, that's what the 'safety ground' is for. ESD's are going to go through the path of least resistance, if your Earth safety ground is good and your case is grounded you have an exceptionally low resistance to that ground so a voltage spike is going to want to go that way instead of through the PC, basically creating a giant voltage divider preventing high voltage from reaching anything in the PC.

What's your thoughts on this statement? BTW, the term "Safety Ground", it that referring to the DVD Drive case grounding to the chassis?

Thanks for your comments!

 

[Mohonri]

What's your thoughts on this statment? BTW, the term "Safety Ground", it that referring to the DVD Drive case grounding to the chassis?

Yes, it's the inherent grounding you get when you secure the drive to the chassis. You'll notice that inside the power supply, there's a fairly hefty wire running from the ground connection on the AC side to the PSU case. The PSU case is then grounded to the chassis via the mounting screws and just plain general contact, and the chassis is connected to the drive via the same method.

 

[lancew70]

Yes, it's the inherent grounding you get when you secure the drive to the chassis. You'll notice that inside the power supply, there's a fairly hefty wire running from the ground connection on the AC side to the PSU case. The PSU case is then grounded to the chassis via the mounting screws and just plain general contact, and the chassis is connected to the drive via the same method.

Thanks for that excellent explanation. BTW, I should correct my last post by noting that the person on the Electo Tech forum also suspects the DVD Drive itself:

You really need to test the DVD drive's case and it's power ground and see if they're connected. If the metal case to the suspect DVD drive connects to it's main ground I'd rule the DVD drive out and look for a bad local ground instead.

 

[lancew70]

I'm not convinced that the PSU isn't at fault. Particularly if it's an intermittent problem, the PSU could seem fine when tested, but still exhibit unusual behavior at other times.

The metal case to the suspect DVD drive shows to be connected to it's main ground.

I contacted PC Power & Cooling today, and they agreed to RMA the PSU in case there is an intermittent problem.

I'm out of things to check/replace other than the Case. I saw some reviews of the Antec P182 and plan on getting one soon, even though I have no reason to suspect the current case.

Edit: Scratch the Antec P182...I see that it also uses the plastic mounting brackets (Sliders). While reviewing other cases yesterday I noticed that the Silverstone TJ-09 (which I might purchase) does not use the plastic mounting brackets. I'll have to confirm this for sure, but it looks as though the peripheral drives mount flush (metal to metal) with the metal cage. Based on the comments I've received, this seems to be a good practice for ensuring a good safety ground.


It's not easy being paranoid and anal retentive at the same time