Talk:Disassembly safety

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Revision as of 19:22, 23 February 2009 by Nicabod (Talk | contribs)
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Removed comments about earth grounding which were overblown, and likely to get someone killed. Workplaces should be grounded through current limiting resistances. The important part is the static conductive work area, not the grounding of said work area. As long as you don't discharge through the motherboard (LCD), everything should be OK. --Wad 00:39, 12 June 2008 (EDT)

Thanks, Wad. This started out as a community-contributed page, so this was a good sanity check to have before making it OLPC-maintained (which, IMO, is a good idea - safety stuff is important to have 100% accurate at any given point in time). Mchua 15:56, 12 June 2008 (EDT)

(I just logged in, after editing the text. Nicabod 19:22, 23 February 2009 (UTC))

Wad, I wrote that extensive commentary about grounding. Would really like to know why you say "likely to get someone killed". Was it that I failed to mention a series protective resistor in the grounding lead? Indeed, if so, that was a serious oversight; I've been retired too long! However, the resistivity of a grounding mat, afaik, is high enough to prevent one from getting a shock. It's improvised metal plates that would be a problem.

Perhaps we should suggest that the protective resistor be something capable of withstanding at least a few hundred volts, short-term; today's resistors can't necessarily take that. I'd say that a 1 meg. carbon comp. should do, although a two-watt size (for voltage withstand, not power dissipation) would be overkill. (A 22 meg. carbon comp. resistor is not limited by power dissipation; it's limited by voltage-withstand capability, as you most likely know.) A resistor with a bulk resistive element rather than a film resistor is better.

If my p.o.v. seems somewhat extreme, it's because I've worked for years in electronics production, where anti-static grounding is taken very seriously; in some shops, we wore heel grounding straps, and one shop had a tester (costly!) to be used daily by everyone for both heel grounders and wrist straps. At least one place had conductive floor tile coating. I felt that some places where XOs are being repaired might not be aware of static risks, and was emphatic in hopes of driving the point home. At the time I wrote that text, OLPC had apparently nothing at all about anti-static provisions.

You might want to remove the discussion about voltages, but I do think it's very important to stress the importance of anti-static procedures. One doesn't know when a device has been degraded by static, and fails at some point in the future.

On the matter of wrist straps, I truly can't accept omitting advice to use them. Cost is hardly a factor, although one can buy some fancy types. They are a mild nuisance, true, but in bad cases, one might, for instance, touch the hinge, shift one's position on a chair, get charged up to a few kilovolts, zap a motherboard, and be mystified by what happened. I think it's appropriate to warn about synthetic fabrics, as well. Nevertheless, you have the final say, and I won't undo your changes. Regards, Nicabod 19:22, 23 February 2009 (UTC)

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