ESD Issue

[JerryH]

I’m looking for help to resolve an ESD issue with my home computer and I hoping someone here will provide some guidance to resolve my issue.

I’ve had two (2) ESD events the past ~4 months that have “Fried my Motherboard” in both instances and I’m trying to resolve why this is occurring from an ESD on the external portion of my case. If it had occurred with me being inside the case, well that would be quite understandable.

I built a new computer this past November and 3 weeks later I reached over to push the button to close my DVD drive tray and I felt a static shock which caused my computer to power off. I assumed the ESD had caused a digital fault but I was not able to get the computer to reboot after un-connecting/reconnecting the power cord from the back of the computer. The front of the DVD drive appears to be hard plastic (not metal).

I live in a dry climate and RH has been very low here. My PC is connected via a Belkin 1100VA USB which is connected to a verified Grounded outlet.

I removed the motherboard and set it up outside the case with minimal components and switched out all the various components including a new Power supply. However, the computer would only power on for 3 or 4 seconds and then shutdown.

I did a close inspection of all components, wiring and connections but could not find any issues. The off-sets for the motherboard to the case have been checked and verified to be correct.

I replaced the motherboard and all was just fine for about 3 months when I was reaching to touch the front of the DVD drive and I felt a static spark and again the computer powered off and I repeated the troubleshooting steps as I did the first time. It reacted the very same…power on for 3-4 seconds and then power off.

I decided to do another thorough inspection of all components and this time I noticed that the Ribbon Cable connected to the DVD drive and motherboard had a small bare wire exposed on Pin 39 which is the Led driver. Also, on there was a small area of exposed wire on pin 1 or 2. The picture does not show it but I looked to see where the bare wire would hit and it looks as though the cable gets pushed up toward the top of the DVD Drive and actually folds back on top of it and the exposed wire hits (or rests very close to) the metal case of the DVD.
(see image below..oops, sorry can't post it)

With the ESD event(s) I've had could this introduce a problem to the mobo? This exposed wire alone might not cause a problem with the DVD operation but I'm wondering if with the ESD introduced whether it could fry something (?chipset)?) on the mobo as it goes to the mobo header.

I have just completed installing a new motherboard and all is fine for now but I’m very uncomfortable in not knowing whether I’ve found the real culprit in my ESD issue. The damaged cable has been replaced.

I know it makes no sense that you could ruin a motherboard from an external ESD event unless there is something not grounded.

I have had all the grounding checked from the outlet to the computer and all is fine. I had the power supply and everything on the computer and all shows to be grounded. I have also replaced the PC Power & Cooling 610 Silencer PS with a Antec Neo 550 (the PCP&C 610 checks out to be operating ok)
I’ve installed a 3M Velostat 4’x8’ electrically conductive mat in front of my desk and computer in hopes of providing some ESD protection.

What's the likelyhood that the ESD induction coupled with the damaged Ribbon cable caused the catistrophic failure of my motherboard. Do you think there is perhaps a short somewhere that is causing this problem?

I'll admit to being very anal retentive but I just want to understand the problem. :):boggled:

[Stupendous Man]

I am not an electrician, but if I were you, I'd consider hiring an electrician to check the grounding on your electrical outlets, particularly the one you use for the computer. They may be a problem that's been undetected since the house was built.

[JerryH]

Thanks for your comment...I have had electricians here on two different occassions and they can't find any grounding problems. Everything checks out fine.

One electrician thinks the damaged ribbon cable was the problem but others have said they don't think it could be the cause of a catistrophic failure of the mobo.

I lean toward the bad cable, but I have no proof.

I'm hoping that perhaps a knowlegeable electrical person will have a good viewpoint on this.

[Pro7]

Thanks for your comment...I have had electricians here on two different occassions and they can't find any grounding problems. Everything checks out fine.

One electrician thinks the damaged ribbon cable was the problem but others have said they don't think it could be the cause of a catistrophic failure of the mobo.

I lean toward the bad cable, but I have no proof.

I'm hoping that perhaps a knowlegeable electrical person will have a good viewpoint on this.

Its your powerbox. The #1 cause for mobo damage comes directly from the powerbox. Apparently the powerbox, whether new or old, is defective.

Have it replaced asap. It happened to me before.

If you determine that its not the powerbox, its your mounts on the mobo.

There are mounts that you have to install on a frame where the mobo sits. You cant just go ahead and use the screws to mount it with, there must be a adequate space between the mobo and the frame, which the mobo is not touching the frame. There are rubber or plastic mounts. Maybe a mobo component such as a soldered item on the backside of the mobo is touching the metal frame seat. (where the mobo sits in)

[JerryH]

Its your powerbox. The #1 cause for mobo damage comes directly from the powerbox. Apparently the powerbox, whether new or old, is defective.

Have it replaced asap. It happened to me before.

If you determine that its not the powerbox, its your mounts on the mobo.

There are mounts that you have to install on a frame where the mobo sits. You cant just go ahead and use the screws to mount it with, there must be a adequate space between the mobo and the frame, which the mobo is not touching the frame. There are rubber or plastic mounts. Maybe a mobo component such as a soldered item on the backside of the mobo is touching the metal frame seat. (where the mobo sits in)

I've checked the PS for grounding and have checked continuity for each of the dc output wires on the PS and it all tests to be ok.

But as I indicated in my original post, I've already chaged the PS and as for the mobo offsets to the case have been tripled checked and no points of contact other than the 9 required offsets.

I think it was the bad ribbon cable touching the DVD drive but only time will verify that. :)

[marting]

I'm a P.E. in E.E. and have dealt with ESD design issues including on my own P.C.

It's unlikely the ribbon cable bare wire was the problem. ESD MoBo failures are due to high current (relatively) surges that couple into any input, particularly low level inputs such as peripheral interfaces. The most likely cause is poor contact with the DVD drive and the chassis. It is critical both sides of the drive be electrically connected to the chassis. Avoid plastic mount sliders that don't provide good metal to metal contact. Also, check your chassis's internal metal housing and make sure it is well grounded and surrounds the DVD drive. Consider replacing the chassis/box. Their ESD/EMI design has improved a lot over the years.

ESD is tricky. A single area of non contact along brackets and covers can create paths for ESD to couple and cause failure internally. Therefore the most important item to change out is the PC box. Look for one where the grounding / shielding has actually been considered. A box designed for low EMI will also provide good ESD protection.

[JerryH]

I'm a P.E. in E.E. and have dealt with ESD design issues including on my own P.C.

It's unlikely the ribbon cable bare wire was the problem. ESD MoBo failures are due to high current (relatively) surges that couple into any input, particularly low level inputs such as peripheral interfaces. The most likely cause is poor contact with the DVD drive and the chassis. It is critical both sides of the drive be electrically connected to the chassis. Avoid plastic mount sliders that don't provide good metal to metal contact. Also, check your chassis's internal metal housing and make sure it is well grounded and surrounds the DVD drive. Consider replacing the chassis/box. Their ESD/EMI design has improved a lot over the years.

ESD is tricky. A single area of non contact along brackets and covers can create paths for ESD to couple and cause failure internally. Therefore the most important item to change out is the PC box. Look for one where the grounding / shielding has actually been considered. A box designed for low EMI will also provide good ESD protection.

Marting... What you say is truly interesting. I'm beginning to think it is not a result of the bad ribbon cable. Others more knowledgeable than me have suggested that it's just not likely that the spark would 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. Would you concur with this reasoning?

I going to do a new inspection of the contact with the DVD drive and the chassis and chassis's internal metal housing to make sure it is well grounded and surrounds the DVD drive.

Edit: My DVD Drive uses the Plastic slider mounts and after inspecting them I can see where it is possible to not make good metal to metal contact (However, the mount screw does go through the metal clip on the slider - that's a small contact area though). My case is a new Antec Solo but I may change it just to be on the cautious side.

Thanks very much for your insight.

[Dan O.]

I haven't fried a mother board but I did kill a couple of mice with ESD. A big spark can actually leave a visible trail from the point of first contact to the circuit trace that absorbed the spark.

The surge from a spark can easily blow out an input gate on the first circuit it reaches. On the mice that I fried I was able to see which gate was blown using a simple voltmeter. Lower energy discharges can be more insidious and leave the gate with a pin hole defect that grows over time. This is why manufacturing needs to take such extreme ESD precautions. Destroying an occasional system in manufacturing is no big deal but selling a system to a customer that fails in a couple of months is very bad for business.

The other thing that can happen with ESD (and also while improperly hot plugging peripherals) is that the whole interface chip can go into an SCR state and effectively short circuit the power supply. If the circuit isn't designed to handle this condition the chip will melt and spray it's guts out when the case splits open. These are usually easy to spot from the debris field.


You want to know what you can do about this ESD problem?

First you must realize that the source of the ESD is yourself. The anti-static mat is a good thought but it isn't going to do any good unless you make contact with it. You could always take you shoes and socks off when you enter the computer room. Simply touching another grounded object before touching the computer will dissipate most of the static charge that you are carrying.

A properly designed case might help but in this instance you are making first contact with the door of the DVD drive. That door may be all plastic except for the wires connecting to the eject button and status LED. You may need to build a small ESD shield that will intercept the static charge before it reaches these wires and safely escort it to ground.

[JerryH]

I haven't fried a mother board but I did kill a couple of mice with ESD. A big spark can actually leave a visible trail from the point of first contact to the circuit trace that absorbed the spark.

The surge from a spark can easily blow out an input gate on the first circuit it reaches. On the mice that I fried I was able to see which gate was blown using a simple voltmeter. Lower energy discharges can be more insidious and leave the gate with a pin hole defect that grows over time. This is why manufacturing needs to take such extreme ESD precautions. Destroying an occasional system in manufacturing is no big deal but selling a system to a customer that fails in a couple of months is very bad for business.

The other thing that can happen with ESD (and also while improperly hot plugging peripherals) is that the whole interface chip can go into an SCR state and effectively short circuit the power supply. If the circuit isn't designed to handle this condition the chip will melt and spray it's guts out when the case splits open. These are usually easy to spot from the debris field.


You want to know what you can do about this ESD problem?

First you must realize that the source of the ESD is yourself. The anti-static mat is a good thought but it isn't going to do any good unless you make contact with it. You could always take you shoes and socks off when you enter the computer room. Simply touching another grounded object before touching the computer will dissipate most of the static charge that you are carrying.

A properly designed case might help but in this instance you are making first contact with the door of the DVD drive. That door may be all plastic except for the wires connecting to the eject button and status LED. You may need to build a small ESD shield that will intercept the static charge before it reaches these wires and safely escort it to ground.

Dan O ... Thanks for the very informative comments and suggestions. Your comments and Marting's make me understand how very little I know about the ESD issue I've been struggling with.

Regarding the 3M Velostat electrically conductive mat, it's 4'x6' and it's in front of my PC and Desk and is connected via the allegator clip (fastened with screw) to a copper wire that goes directly to my external grounding rod. A second cable from the mat has the wrist strip that is positioned right on my desk. It's not impossible, but not likely, that I can reach my PC without standing on the mat. I'm not trying to convience anyone that this is a fool proof setup but rather providing the info in case you see a problem with this.

As to the ESD Shield, are you talking something like a Faraday cage structure using a electrical conductive material (like some packaging material)? My ignorance is showing here I realize :)

Great stuff, thanks for any further comments. :)

[Dan O.]

Regarding the 3M Velostat electrically conductive mat, it's 4'x6' and it's in front of my PC and Desk and is connected via the alligator clip (fastened with screw) to a copper wire that goes directly to my external grounding rod. It's not necessary to go directly to the external ground and in fact it would be preferable to connect the grounding mat to the same local electrical ground that your computer is connected to. If you draw a virtual circle around your PC, everything inside that circle should be connected to a common ground point and all wires crossing that circle should connect to static suppression devices that also connect to that same ground point. This local ground point would connect to your house wiring ground which all connects back to the house ground point which is probably inside the breaker box. The house ground point is then connected to the earth ground. Electrically conductive services that enter your house such as cable and phone should also be connected to the same earth ground point. This grounding network is for protection from lightning which is nothing more than really big static electricity.

If you have more than 1 ground rod on your house they should be connected by a heave conductor that goes around the perimeter of the house. Otherwise a near by lightning strike could enter your house from one ground rod and leave through the other taking whatever it decides is the shortest path which might include up the power cord into your computer, down the USB cable to the mouse, through the operator to the static mat and out to the ground rod.

A second cable from the mat has the wrist strip that is positioned right on my desk. This is good and it would be best if you develop a habit of touching this wrist strap whenever you approach the computer and after you sit down. You shouldn't feel a spark because a proper ground strap has a high resistance cord that safely dissipates the static without creating an electrocution hazard for the wearer if they happen to contact the hot side of the AC line.

It's not impossible, but not likely, that I can reach my PC without standing on the mat.If you are wearing rubber soled shoes you will be insulated from the mat and the static charge that you carry will not be dissipated.

As to the ESD Shield, are you talking something like a Faraday cage structure using a electrical conductive material (like some packaging material)? My ignorance is showing here I realize :) ESD shielding can have a much higher resistance than a Faraday cage. You can even draw anti-static shielding with a soft pencil.

[marting]

A properly designed case might help but in this instance you are making first contact with the door of the DVD drive. That door may be all plastic except for the wires connecting to the eject button and status LED. You may need to build a small ESD shield that will intercept the static charge before it reaches these wires and safely escort it to ground.

This demonstrates the difference between DIY and OEM supplied pcs. OEM's will test during the design for ESD susceptibility by probing around peripherals and i/o devices. Generally, on things like DVD drives, they make certain the drive and facade force sparks to the case before the switches and displays, which are usually recessed somewhat from the front panel to facilitate this.

[JerryH]

It's not necessary to go directly to the external ground and in fact it would be preferable to connect the grounding mat to the same local electrical ground that your computer is connected to. If you draw a virtual circle around your PC, everything inside that circle should be connected to a common ground point and all wires crossing that circle should connect to static suppression devices that also connect to that same ground point. This local ground point would connect to your house wiring ground which all connects back to the house ground point which is probably inside the breaker box. The house ground point is then connected to the earth ground. Electrically conductive services that enter your house such as cable and phone should also be connected to the same earth ground point. This grounding network is for protection from lightning which is nothing more than really big static electricity.

If you have more than 1 ground rod on your house they should be connected by a heave conductor that goes around the perimeter of the house. Otherwise a near by lightning strike could enter your house from one ground rod and leave through the other taking whatever it decides is the shortest path which might include up the power cord into your computer, down the USB cable to the mouse, through the operator to the static mat and out to the ground rod.

This is good and it would be best if you develop a habit of touching this wrist strap whenever you approach the computer and after you sit down. You shouldn't feel a spark because a proper ground strap has a high resistance cord that safely dissipates the static without creating an electrocution hazard for the wearer if they happen to contact the hot side of the AC line.

If you are wearing rubber soled shoes you will be insulated from the mat and the static charge that you carry will not be dissipated.

ESD shielding can have a much higher resistance than a Faraday cage. You can even draw anti-static shielding with a soft pencil.

Great comments.

It's not necessary to go directly to the external ground and in fact it would be preferable to connect the grounding mat to the same local electrical ground that your computer is connected to.

To make sure I understand your comment... The grounding wire that the grounding mat goes to goes to is the same grounding rod that my electrical PC/UPS outlet is grounded to. Is that acceptable or or you saying that it should go directly to the PC/UPS Outlet.

I live in an older home that has the two prong receptacles. That's the reason I installed the 7' copper rod for the 3 prog outlet my PC/UPS is connected to.

If you have more than 1 ground rod on your house they should be connected by a heave conductor that goes around the perimeter of the house. Otherwise a near by lightning strike could enter your house from one ground rod and leave through the other taking whatever it decides is the shortest path which might include up the power cord into your computer, down the USB cable to the mouse, through the operator to the static mat and out to the ground rod.


Wow, I was not aware of this. What is a "heave conductor"? Our spring thunder storms are firing up here even as I post this.

If you are wearing rubber soled shoes you will be insulated from the mat and the static charge that you carry will not be dissipated.


Good point. I'm seaching for Conductive Safety Shoes.

Another question is if the ESD is occurring when touching the trey button on the front of the DVD Drive, why not use an insulation material on the front to prevent prevent or limit the flow of electrons across its surface... or is this just inviting another disaster?

[marting]

Wow, I was not aware of this. What is a "heave conductor"? Our spring thunder storms are firing up here even as I post this.


I'm sure he meant to type "heavy" and he is absolutely right. If you have two earth gnds on opposite sides of the house a wire around them will not only create a path for the current around the house but it will substanitally reduce dB/dt (rate of change of the B field) inside the loop. This changing B field induces a current in conductive loops and can is often responsible for frying electronics.

[JerryH]

I'm sure he meant to type "heavy" and he is absolutely right. If you have two earth gnds on opposite sides of the house a wire around them will not only create a path for the current around the house but it will substanitally reduce dB/dt (rate of change of the B field) inside the loop. This changing B field induces a current in conductive loops and can is often responsible for frying electronics.


Thanks marting :)

[Dan O.]

To make sure I understand your comment... The grounding wire that the grounding mat goes to goes to is the same grounding rod that my electrical PC/UPS outlet is grounded to. Is that acceptable or or you saying that it should go directly to the PC/UPS Outlet.

Everything should tie to the closest local ground point. If the UPS has a separate ground terminal, that would be the best point to use as the local ground. If you have 2 wires going to the ground rod there is the danger that if the primary ground wire became disconnected then the shortest path to ground would be through you through the mat.

I live in an older home that has the two prong receptacles. That's the reason I installed the 7' copper rod for the 3 prog outlet my PC/UPS is connected to.

You wouldn't think of installing a lightning rod and attaching that to your computer. A ground rod is just the other half to the same circuit. What is important in grounding a system is to insure that there is nothing near by that can be at a significantly different potential that might create a path for electricity to flow through the wrong object like a person or the computer. Voltage itself isn't dangerous, it's the current that kills. You want your local ground point to be connected to any conductive elements in the vicinity that you might be able to contact while touching the computer or any of the peripherals. This would include things like heating or water pipes and air ducts. The goal is to conduct the current safely around you and not to specifically give it a place to go. My thought is that the extra outside ground is more of a hazard than a protection unless it is also connected to the main house ground.


Another question is if the ESD is occurring when touching the trey button on the front of the DVD Drive, why not use an insulation material on the front to prevent prevent or limit the flow of electrons across its surface... or is this just inviting another disaster?Even if the plastic is an insulator, the surface can get dirty and conduct. I fixed the problem with zapping mice by adding a thin foil strip around the inside of the case behind the crack where the two halves join and tying this foil to the ground on the cable that goes back to the computer. More modern mice already have this built in or use a conductive plastic for the case.

[JerryH]

Well, Dan O and Marting, between the two of you I'm getting a great learning experience.

I just read on another forum where another person experienced an ESD event while touching the Trey Button on the front of his DVD. In his case, this system did a BSOD and he was able to reboot. If I understand, his resulted in a digital fault which was relieved by rebooting. He may have some latent (walking wounded) issues but at least so far he's not experienced a catastrophic failure.

Regarding your comment about build a small ESD shield that will intercept the static charge before it reaches these wires and safely escort it to ground, would you mind being a bit more specific as to how I can accomplish this?

Thanks very much for all the nice help. :)

[JerryH]

My thought is that the extra outside ground is more of a hazard than a protection unless it is also connected to the main house ground.


Ok, but let me clarify my current situation just to be sure I communicating accurately...

Because I live in an older home that only has 2-prong receptacle outlets, I have in the past couple years driven 2 grounding rods (7') to connect to a couple of 3 prong receptacle that I installed for my 2 PCs (different rooms).

Also, there is a 3rd grounding rod that is on the other side of my house where the electrical power comes in. This grounding rod has a ground wire that runs from the rod to the electrical meter and then down to into the breaker box right below the meter. The neutral and 2 phases come into the house but no ground since the only grounded outlets I have are the 2 that I have installed.

If I'm saying this correctly, then you are suggesting that I use a heavy conductor to tie all three grounds together. Is this correct?

Thanks for your help with this.

[Dan O.]

I was thinking earlier that you had a low profile DVD drive with the button and status light on the tray itself. You probably have a standard configuration with the button and light on the bezel. I popped open one of mine to see what shielding was already in place. 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 it's 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.
http://forums.randi.org/imagehosting/15144460487d4c9d12.jpg (http://forums.randi.org/vbimghost.php?do=displayimg&imgid=4757)
Your DVD is probably similarly equipped and this can't easily be improved. If you want to go overboard, you could paint the bezel with conductive paint and insure that there was a connection between this paint and the DVD case. You would have to research what paint would offer the conductivity and be compatible with the plastic. I've seen a how-to somewhere on the web for instructions on removing the bezel that you should search for if you go that route.

Thinking more about this problem, if the static charge managed to get to the DVD circuitry it should have burned out the DVD and not your motherboard. This further suggests that the DVD was not properly grounded and the charge managed to travel through the DVD interface cable into the motherboard. Insuring that the DVD is grounded will be a big help. If you want more protection you could add a split ferrite RFI reducer to the interface cable.

[marting]

Ok, but let me clarify my current situation just to be sure I communicating accurately...

Because I live in an older home that only has 2-prong receptacle outlets, I have in the past couple years driven 2 grounding rods (7') to connect to a couple of 3 prong receptacle that I installed for my 2 PCs (different rooms).

Also, there is a 3rd grounding rod that is on the other side of my house where the electrical power comes in. This grounding rod has a ground wire that runs from the rod to the electrical meter and then down to into the breaker box right below the meter. The neutral and 2 phases come into the house but no ground since the only grounded outlets I have are the 2 that I have installed.

If I'm saying this correctly, then you are suggesting that I use a heavy conductor to tie all three grounds together. Is this correct?

Thanks for your help with this.

I'm afraid we are starting to mix human ESD issues and lightning ESD. Lightning can cause large transients and big voltage differentials between things like the AC lines, the RF cable attached to a cable modem, phone modems and DSL and such. The best way to reduce hazards from these is to get a power distribution box with built in line filters and pass through filters for phone/cable modems. They have good instructions on how to use them and are fairly cheap. High transients from lightning are stopped at the distribution box and don't proceed down your power line, 1xxx base T connector or phone line.

For people based ESD, a good practice is to always touch the computer case before pushing buttons on it or touching USB, flash, or CD/floppy drives.

[marting]

Thinking more about this problem, if the static charge managed to get to the DVD circuitry it should have burned out the DVD and not your motherboard. This further suggests that the DVD was not properly grounded and the charge managed to travel through the DVD interface cable into the motherboard. Insuring that the DVD is grounded will be a big help. If you want more protection you could add a split ferrite RFI reducer to the interface cable.

I agree with Dan's take.

[Dan O.]

Ok, but let me clarify my current situation just to be sure I communicating accurately...
If I'm saying this correctly, then you are suggesting that I use a heavy conductor to tie all three grounds together.

Building codes require that there is only 1 electrical ground for the building. Having the 3 ground rods tied together might qualify as a single ground but you would have to use a very heavy conductor like a 1/2 in. pipe. A better option would be to get an electrician to run a grounded power line from the electrical breaker box for your computers and remove the extra ground rods. If you have an accessible attic or unfinished basement, running the wire shouldn't be that much of a problem. While you are at it, run a grounded service to the kitchen and bathroom and install a GFI.

[JerryH]

Thinking more about this problem, if the static charge managed to get to the DVD circuitry it should have burned out the DVD and not your motherboard. This further suggests that the DVD was not properly grounded and the charge managed to travel through the DVD interface cable into the motherboard. Insuring that the DVD is grounded will be a big help. If you want more protection you could add a split ferrite RFI reducer to the interface cable.

I think I understand but to be sure, my understanding is that electrical grounding for the DVD Drive is handled through the power cable grounds. When you say DVD interface cable are you referring to the power cable or the ribbon cable? I can't post a photo here yet but the exposed wire on the ribbon cable was very close or may have actually been contacting the metal surface of the DVD Drive. Sorry, but I just want to be sure I grasp what you saying.

Thanks

[Dan O.]

The DVD case needs to be grounded to the PC case. The farrite RFI reducer goes around the ribbon cable.

The DVD power ground does connect to the DVD case inside the DVD. But for some reason this connection was not sufficient to prevent zaping the motherboard in your system. If there is a knot in the cable or it's wrapped up in a coil it might prevent all of the static pulse from passing. Those disposable anti-static wrist straps that come with memory upgrades have a few inches of sticky copper foil on one end. That stuff should be perfect for bridging components to create the shortest possible ground path for static electricity.

[JerryH]

The DVD case needs to be grounded to the PC case. The farrite RFI reducer goes around the ribbon cable.

The DVD power ground does connect to the DVD case inside the DVD. But for some reason this connection was not sufficient to prevent zaping the motherboard in your system. If there is a knot in the cable or it's wrapped up in a coil it might prevent all of the static pulse from passing. Those disposable anti-static wrist straps that come with memory upgrades have a few inches of sticky copper foil on one end. That stuff should be perfect for bridging components to create the shortest possible ground path for static electricity.

This is a great education I'm getting thanks to you and marting...and it's even starting to fit together and make sense. I truly believe that this thread will serve as a excellent source of information for others like me when dealing with ESD events related to Computers.

Dispite my attempt to put the bad ribbon cable into the equation, are you still concurring with what marting said earlier that It's unlikely the ribbon cable bare wire was the problem. ESD MoBo failures are due to high current (relatively) surges that couple into any input, particularly low level inputs such as peripheral interfaces.


I guess I still want that bare wire on the faulty ribbon cable (potentially touching on the metal DVD Drive) to be apart of this issue but from what you and marting are deducing, it's not an issue is this case. Correct?

Thank you

[JerryH]

Building codes require that there is only 1 electrical ground for the building. Having the 3 ground rods tied together might qualify as a single ground but you would have to use a very heavy conductor like a 1/2 in. pipe. A better option would be to get an electrician to run a grounded power line from the electrical breaker box for your computers and remove the extra ground rods. If you have an accessible attic or unfinished basement, running the wire shouldn't be that much of a problem. While you are at it, run a grounded service to the kitchen and bathroom and install a GFI.

Ok,I think I understand now, lets see...

1. As they exist now, my 2 isolated ground rods are useless for equipment grounding. To function properly they must be bonded (securely attached electrically) to the grounded service conductor. (Mine aren't).

2. In the event of an equipment failure, the fault current should travel along the ground wire and then back to the source. In a normal and proper setup this happens at the point where the ground and neutral are connected. This is usually at the main circuit breaker panel in the house. although it could be at the main disconnect near the meter (as in my case).

3. In my existing configuration, I have no path for any fault current, other than through the soil... In other words, I have no fault path for fault current.

So, I should do as has been suggested by running a grounded power line from the electrical breaker box for my computers and remove the extra ground rods, or... install brand new circuits run from the panel to new receptacles.

Have I got it? :)

Thank you

[Dan O.]

I think you've got it.

I've been trying to find a reference to what would be required to bond the three ground rods. The greatest hazard I see is a near by lightning strike that would create a voltage deferential between two ground points. If these two grounds were connected by a small wire inside your house, this wire could get hot enough to start a fire.

I don't know if electrical codes allow running a separate ground wire to upgrade 2 wire circuits. It's certainly better than no ground but check this with an electrician in your area.

[JerryH]

I think you've got it.

I've been trying to find a reference to what would be required to bond the three ground rods. The greatest hazard I see is a near by lightning strike that would create a voltage deferential between two ground points. If these two grounds were connected by a small wire inside your house, this wire could get hot enough to start a fire.

I don't know if electrical codes allow running a separate ground wire to upgrade 2 wire circuits. It's certainly better than no ground but check this with an electrician in your area.

Thanks Dan... I don't know if this helps but I received it from another source regarding my grounding rods and bonding them together:

There is no limit to the number of ground rods that a electrical service can have....actually (IMO) the more the better.

If all that exist are ground rods for the grounding electrodes....this means no water pipe used as the grounding electrode, no foundation steel used as the grounding electrode...only ground rods on the system to provide earth grounding....then...in my opinion...it is allowed to use a #6 copper conductor as bonding jumpers to bond all of the ground rods together and connect (bond) them to the service (power company) ground to make them part of the grounding electrode system.

In my opinion...If the (#6) bonding jumper is not exposed to damage, it can run exposed (attached) along the outside of the house, under the house or buried underground.

Also...IMO... Two (listed) clamps on each ground rod must be used to attach the #6 copper to the rod....either that or use one continuous piece....two wires can't be put under the same clamp...
Find the ( 2005) National Electrical Code and read 250.53, 250.58, 250.64, 250.66, 250.68, 250.104.

Again...In my opinion...After the ground rods are effectively bonded together and to the service ground, a equipment grounding conductor can be run from isolated receptacles and bonded (with listed connector) to the ground rods or bonding jumpers (between the rods) at the closest point.
Read 250.130(C).
Remember....The equipment grounding conductors and bonding conductors have to be free from exposure to damage after installed.

From your post, it sounds (to me) like all your system needs is bonding of all of the ground rods together and back to the service ground..using minimum #6 copper.
The equipment ground wires (the ones from the receptacles to the ground rods or bonding jumpers) need to be #12 copper (or larger) for a 20 amp circuit, #14 copper (or larger) for a 15 amp circuit, and #10 or larger for a 30-60 amp circuit.


What do you think. Agree/disagree??

[De_Bunk]

If i ever open my case...I strip down ( Not always the practical thing to do at work ) and 'static' myself out..with an 'Earth strap'...

And i'd advise everyone to get one..they are cheap and could save you a whole load of $$$.

DB

[Macoy]

i saw one where a pci card (modem)vibrated partially loose after a long journey and on boot jiggered the psu, which proceeded to spike the system (the owner was unaware of the problem) until the hd packed up. he was lucky not to lose the mb too.

[Dan O.]

The #6 wire may be good enough but you should check with your local electricians because building codes vary. I was seeing #4 mentioned in some locations. It should also be possible to solve the equations to come up with the proper wire size but I'm too lazy to do it right now.

The wrist strap and portable ESD ground pad are in my tool kit. I also avoid synthetic clothing so there is less static generation.

[JerryH]

I have an electrician that will be at my house tomorrow to look over my situation and install the proper grounding components/system. (New circuts for my PCs, perhaps depending on costs.

Dan O and Marting, a great big thanks to you both for helping me with my problem and being patient with my ignorance. It's been an excellent learning experience for me.

It just goes to show me how a DIY'er like me can get out on a limb when I stray to far from good professional help. :)

Big thanks again.

JerryH

[JerryH]

I received some review comments from other knowledgeable persons who also thought that my problem was the result of the DVD Drive not being properly grounded.

However, when I mentioned that I was told that years ago every internal drive featured a grounding tab that could be connected to the computer's metal case, but nobody ever grounded them. So these days the electrical grounding is handled through the power cable grounds.

In response to this statement I was very interested in a couple responses that said the following:

The power ground is not an acceptable ground for ESD. 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.

So, if I understand it would seem that the DVD and other peripheral devices should rely on a good metal to metal ground on the PC case chassis rather than the power ground.

But, in my new Antec P180 case, which is designed for quiet operation, the drives are mounted in a cage with huge silicone rubber washers that completely isolate the drives from mechanical contact with the case.

Does this seem odd or am I missing something here.

BTW, another EE that reviewed my issue stated that he felt the DVD drive is the most likely culprit but that he also was 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.

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

Thanks for any further comments:)

[marting]

But, in my new Antec P180 case, which is designed for quiet operation, the drives are mounted in a cage with huge silicone rubber washers that completely isolate the drives from mechanical contact with the case.

Does this seem odd or am I missing something here.


This is perfectly ok for the hard drives which are not accessible and can't draw an esd discharge. This is not ok for dvd/cd/floppy drives which must be available from the front of the chassis unless provisions are made to avoid external discharge to the dvd.

[JerryH]

This is perfectly ok for the hard drives which are not accessible and can't draw an esd discharge. This is not ok for dvd/cd/floppy drives which must be available from the front of the chassis unless provisions are made to avoid external discharge to the dvd.


marting...What you say makes sense to me now. There seems to be a consistent and growing consensus that the DVD Drive was simply not grounded.

A few others still think perhaps the PSU could be the problem ( and I don't rule it out either) but that is really difficult to establish. The grounding of the DVD Drive just makes good sense to do, period.

Anyone have a good source/link for conductive tape to ground the drives in my various computers?

[JerryH]

oops! double post. Mod please delete.

[marting]

Jerry,

Esd protection is more involved than adding a ground strap to the DVD. The problem with esd is that it generates a very rapid change in current (di/dt) which creates a rapidly changing "B" field which in turn causes a voltage change. In addition, the "B" field induces voltages in other conductors. The dvd should be mounted in the metal chassis enclosures with a good ground on both side of the dvd to the chassis.

As for the MB and PS, they both can be problematic since wires run to the front panel from both. It's been a long time though that I've seen esd problems from these areas with current chassis and power supplies, probably as a result of work to make the computers pass FCC B and EU radiation specs.

[JerryH]

The dvd should be mounted in the metal chassis enclosures with a good ground on both side of the dvd to the chassis.


marting...Thanks for the excellent explanation.

So far, I've not located any of the metal sliders that fit these newer peripherals and my Antec Solo case.

I have some metal sliders for peripheral drives that came with one of my older PC Cases but I don't think I can mod them to fit my existing case. They are too wide to slide on to my case.

I need to find some metal sliders that are the same size as the plastic ones. That's one of the reasons I got to thinking about the conductive tape (prior to your post tho).


Below you can see how one of the plastic sliders fits in my case. It slides between the cutouts (donuts). The metal sliders are too wide to fit.



http://img518.imageshack.us/img518/319/plasticsliderincaseeu4.th.jpg (http://img518.imageshack.us/my.php?image=plasticsliderincaseeu4.jpg)

[JerryH]

Edit:

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.

Those plastic mounting brackets (Sliders) might make for a quiter operation but an effective Safety Ground makes more sense.