ESD Issue? Kind of long - Page 2 - Electronic Circuits Projects Diagrams Free

Peach · 7th April 2007, 02:39 PM

Quote:

Originally Posted by Sceadwian

Just because the DVD drive was the entry point for the ESD doesn't mean it was at fault, you're after all going to hit that one button more than almost any other on your system if you use your DVD drive a lot. Since you've said that the DVD's case is connected to it's power ground either the ohmic connection between power ground and case ground is weak, or the local ground itself is faulty (not being of sufficiently low impedance during an ESD to sacrificially draw the current away) The kind of failure you're talking about is virtually impossible to trace if everything is grounded. Because you need to determine the individual components impedance to the power ground during a massive voltage/current pulse, IE under loads which aren't practicle to test at with home made equipment.

It's a needle in a haystack, and the haystack is made up of needles.

Sceadwian...Thanks for your informative comments. I certainly agree with your analogy using the haystack made up of needles. That seems very appropriate to me

I do agree with your comment:

Quote:

Just because the DVD drive was the entry point for the ESD doesn't mean it was at fault...

Notwithstanding your comment, I did learn a bit more about the plastic drive mounting brackets on my case. I have some metal mounting brackets that came with an older case but they do not fit on my Antec Solo case that came with the plastic mounting brackets (Sliders). The metal brackets are wider and it would be difficult to mod them to fit. 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.

However, 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.

A comment posted on another site has made me change my mind about using conductive copper tape to improve the ground of the DVD Drive:

Quote:

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.

Thank you for your comments

Sceadwian · 8th April 2007, 01:31 AM

Ahh, sorry about that, I wasn't paying close enough attention to the plastic mounting brackets comment. Every drive of any kind I have ever used has metal to metal contact between the device case and system case, I was just mentally assuming this existed, the picture helps a lot. I wish more people used images. I've never seen plastic mounting brackets like that before, and I'd immediately throw them out the window if I did =)

Peach · 8th April 2007, 01:42 AM

Quote:

Originally Posted by Sceadwian

Ahh, sorry about that, I wasn't paying close enough attention to the plastic mounting brackets comment. Every drive of any kind I have ever used has metal to metal contact between the device case and system case, I was just mentally assuming this existed, the picture helps a lot. I wish more people used images. I've never seen plastic mounting brackets like that before, and I'd immediately throw them out the window if I did =)

Sceadwian...I did confirm from owners of the Silverstone TJ09 that the drives attach metal to metal using screws. I plan to order this new case next week.

BTW, I have sent Antec an Email asking about the use of the Plastic Mounting Brackets and relating my failed mobo experience. I'm just curious to see what they say. I noticed that even their most expensive case uses these. The only reason I can think of why they would use the plastic brackets is for quieter operation. A solid safety ground would seem more important.

Thanks again for your very informative comments and help.

Sceadwian · 8th April 2007, 02:03 AM

Good luck with your future system, you could also create a grounding point on the outside of your case to touch before you touch any other part of the system. Most cases are painted or otherwise insulated from the chasis material itself, but you could put in some kind of direct metal contact to the chasis that you just get into the habbit of touching before you do anything with the computer, or otherwise make the immediate environement less prone to static build up (conductive mat or more grounding points)

Peach · 8th April 2007, 02:18 AM

Quote:

Originally Posted by Sceadwian

Good luck with your future system, and if you don't want to worry about this problem too much in the future and your environment is really that bad for static create for yourself some easily touchable point on your desk and connect it via high gauge wire to the case somewhere, it wouldn't take much effort to make a very unobtrusive grounding point that you could train yourself to grab onto firmly before touching the PC. Or figure out how to otherwise safely ground the immediate environment near the computer.

Great advice! Will this work?

I currently have a 3M Velostat electrically conductive mat (4'x6') in front of my desk and PC. The mat is connected (via a cord) to the metal screw on my grounded 3-prong receptacal. The mat also has attached to it a snap-on cord with a wrist strap that I have attached to the top of my desk that I touch before touching my PC. I also use this grounded wrist strap when inside my PC.

Whew!...now for my Conductive Safety Shoes

Sceadwian · 8th April 2007, 02:31 AM

You have all that and you still got an arc to the PC? or is the mat new? I've never used a ground strap in my life, all you have to do is touch the PC case itself and you're instantly grounded.. Invest in a humidifier for the area or something! If after touching a grounded object for a few seconds you're still able to produce an arc a short timer later something weird is going on.

Peach · 8th April 2007, 02:47 AM

Quote:

Originally Posted by Sceadwian

You have all that and you still got an arc to the PC? or is the mat new? I've never used a ground strap in my life, all you have to do is touch the PC case itself and you're instantly grounded.. Invest in a humidifier for the area or something! If after touching a grounded object for a few seconds you're still able to produce an arc a short timer later something weird is going on.

No, the mat was added after the 2nd failed mobo. Since adding the mat, I've not experienced any ESD arc. I wish I had remembered to touch the metal on the back of my PC case, I most likely would not have ever had a problem.

However, my desk and PC have been in this exact same location for 10+ years and I never had an issue with ESD and so I was not in the habit of touching the metal on my case prior to these latest events.

I've had 4 different PCs I've built in this same location and never a problem until building the new system I have now. So that's why the ESD/or whatever it was, seemed to be isolated to something in the new PC rather than my residential electrical system (not that something could not have changed with my electrical system...but it has been thoroughly checked twice). Come to think about it, I've built/repaired a couple dozen other computers for others in this same space without ever experiencing an ESD issue.

Seems like my problems has to be the Plastic Mounting Brackets or PSU. ???

My PC Specs:
ASUS M2N-E
AMD 64 X2-5200+
2GB Corsair XMS PC2-6400
GeForce 7900gt Ko

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8th April 2007, 01:31 AM	(permalink)
Sceadwian	Ahh, sorry about that, I wasn't paying close enough attention to the plastic mounting brackets comment. Every drive of any kind I have ever used has metal to metal contact between the device case and system case, I was just mentally assuming this existed, the picture helps a lot. I wish more people used images. I've never seen plastic mounting brackets like that before, and I'd immediately throw them out the window if I did =) __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har." Last edited by Sceadwian; 8th April 2007 at 01:35 AM.

8th April 2007, 02:03 AM	(permalink)
Sceadwian	Good luck with your future system, you could also create a grounding point on the outside of your case to touch before you touch any other part of the system. Most cases are painted or otherwise insulated from the chasis material itself, but you could put in some kind of direct metal contact to the chasis that you just get into the habbit of touching before you do anything with the computer, or otherwise make the immediate environement less prone to static build up (conductive mat or more grounding points) __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har." Last edited by Sceadwian; 8th April 2007 at 02:06 AM.

8th April 2007, 02:31 AM	(permalink)
Sceadwian	You have all that and you still got an arc to the PC? or is the mat new? I've never used a ground strap in my life, all you have to do is touch the PC case itself and you're instantly grounded.. Invest in a humidifier for the area or something! If after touching a grounded object for a few seconds you're still able to produce an arc a short timer later something weird is going on. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."