07-03-2003, 11:09 PM
Hi,
Not a bad idea, if you are always careful about never working on any powered circuit, but really bad advice to give. Too many people aren't careful. There was a local kid managed to kill himself last year, cleaning out his power supply. It happened that the live and neutral wires were crossed in it from the manufacturer, even though it was turned off, it was still hot.
Also, if you are going to putz around inside your 'puter with a grounded instrument, remember you also have at least one battery on the motherboard supplying power for the BIOS settings and clock.
I agree that care must be taken when working around electrical devices. I don't consider that a major consideration in reference to personal computers. A few points:
1) One should always disconnect any appliance from the mains before doing any work. If troubleshooting and power is needed, then extreme caution should be used.
2) With the exception of inside the power supply, the voltages in a computer are not harmful (±12V and ±5V DC). The power supply must be removed from the case to be opened and that is almost impossible to do without removing the power cord. Now, some old computers do have a 120VAC switch that is exposed, but even that has disappeared from newer computers. The possibility of harming oneself working on a computer is very small.
3) Most BIOS batteries are the little disk types. Since circuit boards are mostly silk screened and varnished, it requires quite a bit of effort to short out that battery, and even if it happens, it is a small matter to replace it.
By the way, after 30 years of working in electronics, I can just about count the number of cases of static damage I've had on one finger. Common sense goes a long way, too bad it's so rare.
I don't want to cast aspersions on your abilities, but I will ask how you know you've only had one. Most electrostatic damage doesn't fry the component immediately. The damage is a lot more subtle and insidious than that. Which is why places where the damage can have dangerous consequences (such as aerospace and military) take what might seem to be extreme precautions. For more on this do a Google search on "electrostatic damage electronics" and you will learn that a lot more damage is caused than many experienced workers in the field realize and that most of the damage is not detected until much after it is caused. I spent seven years intentionally destroying electronics to qualify them for space applications. Much of what crossed our labs, even though it was new, had been ESDed before we got it. Only microscopic examination would reveal it.
A competitor of mine managed to blow every 'puter in an office, when they used the air hose that was available in that location. Steel tank, brass nozzle, zap! :)
Shop air is never a good idea for cleaning anyway. The oil in most shop air will leave a film on the boards that will combine with dust to form something not unlike cement. Cleaning that mess is almost impossible. Filtered, dry, shop air doesn't have that problem, but unless the air is mainly used for spray painting, it is rarely clean. And, of course, the static problem is very large with moving air -- however, a grounding strap will solve that problem, too (with or without a meg or so in-line).
--Pete
Not a bad idea, if you are always careful about never working on any powered circuit, but really bad advice to give. Too many people aren't careful. There was a local kid managed to kill himself last year, cleaning out his power supply. It happened that the live and neutral wires were crossed in it from the manufacturer, even though it was turned off, it was still hot.
Also, if you are going to putz around inside your 'puter with a grounded instrument, remember you also have at least one battery on the motherboard supplying power for the BIOS settings and clock.
I agree that care must be taken when working around electrical devices. I don't consider that a major consideration in reference to personal computers. A few points:
1) One should always disconnect any appliance from the mains before doing any work. If troubleshooting and power is needed, then extreme caution should be used.
2) With the exception of inside the power supply, the voltages in a computer are not harmful (±12V and ±5V DC). The power supply must be removed from the case to be opened and that is almost impossible to do without removing the power cord. Now, some old computers do have a 120VAC switch that is exposed, but even that has disappeared from newer computers. The possibility of harming oneself working on a computer is very small.
3) Most BIOS batteries are the little disk types. Since circuit boards are mostly silk screened and varnished, it requires quite a bit of effort to short out that battery, and even if it happens, it is a small matter to replace it.
By the way, after 30 years of working in electronics, I can just about count the number of cases of static damage I've had on one finger. Common sense goes a long way, too bad it's so rare.
I don't want to cast aspersions on your abilities, but I will ask how you know you've only had one. Most electrostatic damage doesn't fry the component immediately. The damage is a lot more subtle and insidious than that. Which is why places where the damage can have dangerous consequences (such as aerospace and military) take what might seem to be extreme precautions. For more on this do a Google search on "electrostatic damage electronics" and you will learn that a lot more damage is caused than many experienced workers in the field realize and that most of the damage is not detected until much after it is caused. I spent seven years intentionally destroying electronics to qualify them for space applications. Much of what crossed our labs, even though it was new, had been ESDed before we got it. Only microscopic examination would reveal it.
A competitor of mine managed to blow every 'puter in an office, when they used the air hose that was available in that location. Steel tank, brass nozzle, zap! :)
Shop air is never a good idea for cleaning anyway. The oil in most shop air will leave a film on the boards that will combine with dust to form something not unlike cement. Cleaning that mess is almost impossible. Filtered, dry, shop air doesn't have that problem, but unless the air is mainly used for spray painting, it is rarely clean. And, of course, the static problem is very large with moving air -- however, a grounding strap will solve that problem, too (with or without a meg or so in-line).
--Pete
How big was the aquarium in Noah's ark?