ESD And My Amiga's Serial Port

[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

[guest7146]

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.)

Of course it makes sense for external ports to be as robust as possible, but electronic circuits by their very nature are sensitive to high voltage discharge.  With ESD you're talking about thousands of volts.  It is possible to damage your Amiga if you discharge through the I/O ports.

If you touched an I/O pin then it doesn't mean you definitely damaged your Amiga.  It depends whether you were carrying a high enough static charge at the time.  My guess? I'm betting your Amiga will be fine.  But, in future, if you're worried about it, then just discharge yourself first.

Apple Hammer

[guest7146]

Here's a good tutorial about ESD:

http://www.radio-electronics.com/info/electronics-design/esd/what-is-basics-electrostatic-discharge-tutorial.php

The tutorial covers most aspects of ESD including latent defects (those that cause failures after the event) and there is also a section on sensible design to resist static discharges for external I/O ports and stuff like that.  Check it out, you'll find it interesting!

Apple Hammer

[Photon]

Just wanted to address the few posts with mumbo jumbo bull**** in this thread.

First off, ESD applies mostly to large volume handling of chips, not ports. 8520 are sturdy IO DIL chips from the 80s era which do have static protection.

Secondly, ESD damage is a statistic (and a slight one at that), not an inevitable result. If you don't pet the cat and rub your wool socks on the synthetic carpeting of your floor while diddling your Amiga ports, you're fine.

That said, the old habit we all had when we were teens, to put the Amiga on the carpeting of the living room floor and inserting joysticks with grounded metal case parts (hello Tac-II ?) will - sooner rather than later - zap one 8520 chip. But I think we don't do that much nowadays, am I right?

If you zap your Amiga (you will know because you will feel the tiny jolt), replace the 8520 and you'll be up and running again.

And finally, if you insert something into the Amiga holding it by the plastic, you can't damage your Amiga. If you hold it by the metal (hello Tac-II again), just touch the metal shield by the ports. Whether your Amiga is on or off has NOTHING to do with static damage. (This means that if you get damage, it's because you've inserted a live peripheral such as monitor or joystick with autofire or LED in a very mentally handicapped way and nothing else. Turn the Amiga off before inserting such and you'll be fine.)

Any other damage you experience is due to bad ground or no ground (2 pin mains plug somewhere in the chain), or faulty peripherals or cables going bad-> shorting inside.

Don't blame some ESD ghost before you've checked your equipment. The best way to zap your Amiga is connecting voltages and bad grounds to it such as unchecked sound equipment, serial null cables for PC off ebay with more than 3 wires in them, some old laser printer or some SCART cable with RGB widescreen support.

Summary: unless you keep your Amiga on a synthetic-carpet floor, you can completely let go of your unbased ESD fears.

[freqmax]

Ground yourself before poking around with the signal pins.

[Zac67]

The ports are protected by EMI circuits, so they will survive some static discharge. However, there's a limit to that protection, so it's smarter to limit the voltage by e.g. touching the metal shielding before touching the signal pins.