ESD And My Amiga's Serial Port

[Super TWiT]

First off, I wanted to say that my Amiga is FINE, no esd damage was done, but I want to know if I should have been more careful. I was using my amiga today and realized that there was some gunk on one of my serial port pins. I then unplugged the computer completely, and took a pair of metal nail clippers and used the scrapper part to get the gunk off. Could I have exposed the computer to static with this? I didn't even think of grounding myself because I wasn't inside the case. Was I lucky or am I being paranoid? (Now that i think about it, I had washed my hands about 15 minutes earlier!)

[Trev]

I suspect it's no worse than plugging something into the port or carrying the Amiga around outside a clean room.

[Super TWiT]

So I am probably being paranoid?

[pan1k]

Yes

[guest7146]

Well, in theory it is of course possible to zap your Amiga via the I/O ports, especially if you're walking about on a carpet or something like that because you can really build up a significant charge in that case.  In practice the risk to your machine is low because the I/O ports are all contained within a metal screen that connects to the DType connector.  This "screen" is connected to ground so if you did zap it with an electro-static discharge it would most likely be conducted down to ground and cause no actual damage to your machine.

It's not impossible to cause damage to your machine in the manner you've described but the risk is low and as has already been mentioned you're taking the exact same risk any time you handle the machine, transport it around or plug anything into it.  Ideally you should have earthed yourself, but most people in the same situation probably wouldn't have bothered.  Sometimes it's useful to just touch a radiator or some other earthed piece of metal before you handle the machine so that any charge you've built up whilst trouncing about on the carpet is discharged before you handle the machine itself.  This isn't a total protection from ESD but it's a quick an easy way to significantly reduce the risk.

ESD is a much bigger problem in terms of risk of damage when you're handling components prior to fitting into the PCB.

Apple Hammer

[Super TWiT]

I didn't clean it on carpet, and I even was barefoot (supposed to ground better) And I live in a humid environment (to top it all off it just rained) How am I taking the same risk everytime I move the machine or plug something in as the pins that connect are insulated?

[Tenacious]

If your house was wired in the last 30 years, you probably have properly grounded outlets.  This is easily checked with a meter.  If your 500 is plugged in but turned OFF,  the computer's ground plane is connected thru the house wiring to "earth".  When these conditions are met, your computer is pretty safe.

Far more Amiga ports have been fried by pluggin and unplugging stuff (like joy sticks, printers, modems) while the computer is powered ON.

[guest7146]

How am I taking the same risk everytime I move the machine or plug something in as the pins that connect are insulated?

Well, because if you have built up a static charge and then you handle your machine or go to plug something in, then potentially you could zap an I/O port or something like that.  You don't have to actually touch the pins to zap them either, since we're talking about thousands of volts for a static discharge.

But the point I (and, I think the others) were trying to make is that the risk is very low.  So no, you should not really have been concerned about what you were doing.  But, if you are a bit paranoid about ESD (I am a little bit, too) then you can discharge yourself prior to handling the machine by just touching a grounded point in your home such as a radiator or something like that.  This won't protect against any static charge you build up afterwards, but it will ensure that any charge you currently had built up is gone before you touch the machine.

Walking around on a carpet can cause a significant charge to build up on your body.  As can the rubbing of your clothes while you move around and stuff like that.  The magnitude of the charge depends on lots of things, but mainly the materials that are rubbed together.  So some types of clothes will be worse than others.

Apple Hammer

[Super TWiT]

Apple Hammer I was wondering how the pins in a serial port are incased in metal screen. The space between the pins is plastic. Are you referring to the metal part of the casing on the serial port, and how can you know this is grounded?

[paul1981]

If you live in a hotter climate (without radiators), then kitchen/bathroom sink taps/copper pipes will do as well for discharging yourself.
I've had quite a few nasty static shocks, ones where it does hurt, so better to be safe than sorry is my opinion - especially where Amiga's are concerned.

[guest7146]

Yes, I am referring to the metal part of the casing on the serial port, which is the part you'd be most likely to touch by accident I guess.

How do I know it is grounded? Well, only because it is common practice to connect the metal part of the casing to 0V.  It's not connected to "earth", but it's usually connected to the 0V rail on the secondary side of the power supply, which most components use as their "ground" reference.  The connection to 0V on these connectors is for screening purposes mainly (to reduce interference & noise), not for ESD protection or anything like that.  But, if you were to accidentally discharge a static build up onto the 0V supply rail via the metal part of the connector then this would be a lot less likely to cause damage to the machine than if you were to discharge via one of the I/O pins.

As I say, if you're paranoid about zapping your machine (like I am) either wear an anti-static wrist strap (safest option) or, for a little peace of mind, earth yourself by touching an earthed piece of equipment before handling the machine.  A radiator is my favourite.

I feel compelled to add that you should never ever follow this advice whilst poking around inside the cover of a dangerous piece of equipment where high voltages are involved.  If you're working on dangerous, live equipment (in which case you should be a qualified Electronics Engineer) then you generally should not earth yourself at all, and certainly not via your other hand because if you earth yourself with one hand and take a shock with the other it can be game over as the electric current takes a path through your arm, through your heart (stopping it in the process) and then out through your other arm!

Of course, there is no such danger involved when handling an Amiga computer so it can be a good idea to just tap a radiator or something like that before you muck about with the machine so that you know you've discharged any static build up from your body.

Apple Hammer

[guest7146]

I've had quite a few nasty static shocks, ones where it does hurt, so better to be safe than sorry is my opinion - especially where Amiga's are concerned.

Yep.  A good demonstration of this is to switch on an old CRT monitor from cold whilst rubbing your hand over the screen.  After a few seconds you'll have built up a rather nice static charge indeed.  Touch an earth after that and you'll literally feel and hear the static discharge! Or, if you're evil, you can touch a person standing next to you and then you'll give them a static belt.

Or, if you've got a nice woolly jumper or something like that and you rub it together with itself in the dark, you'll see the sparks jumping around.  This kind of static build up can happen just from natural moving around, so you can carry quite a significant static charge without being aware of it.  Zap your Amiga, and you can damage it quite easily.

Apple Hammer

[paul1981]

Or, if you're evil, you can touch a person standing next to you and then you'll give them a static belt.
Apple Hammer

I wonder if Cammy has one of those? :roflmao:

[Super TWiT]

The thing is, how much protection should one take? I mean I even read on a website that if you zapped a component, you may NOT EVEN KNOW UNTIL MONTHS LATER! What!? That seems highly unlikely. Also, it seems that components have to be able to withstand some ESD to be sold via the ESDA. I believe external ports have to be more roboust than internal equipment too. (By the way, I think I did touch an I/O pin.)

[guest7146]

Hi Super TWiT,

The website you read was absolutely right - you can indeed damage a component via a static discharge and not see any symptoms for months or even years!
This is because a static discharge is not guaranteed to cause a catastrophic failure.  Often it just compromises the component, and in so doing it significantly reduces the life of the device.  For example, say that you zapped an I/O pin on an IC and the discharge compromised the internal routing of the IC.  This could mean that the current carrying conductor inside the chip is no longer capable of handling the current it is designed to, so eventually, after months of use, the conductor eventually fails and then the symptom of the original static discharge is shown.

This is why in electronic factories ESD is taken so seriously.  Where I work you have to wear an anti-static footstrap at all times, and you have to test yourself twice a day and sign a form to say you've done it.  If you sit at a bench and handle products then you must wear an anti-static wrist strap, and the bench must be ESD approved as well.
Electronic manufacturers take these precautions because a static discharge can significantly reduced the life of their products.  A product could be compromised by a static discharge whilst in the factory and still pass all of its functional tests.  The product then goes out to the customer an a failure is experienced in the field some time later.  The time it takes for the failure to finally occur is unknown.  It could be hours, days, weeks, months, even years.

Apple Hammer