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posted by martyb on Sunday August 30 2020, @01:32PM   Printer-friendly
from the of-course-it-is-impossible-to-get-online-using-a-desktop dept.

US Laptop Shortage Could Derail Remote Learning:

As students and teachers prepare for a return to in-person learning for at least some of the time this fall, many of the nation's schools are facing shortages and delays for laptops and tablets needed for online learning, an Associated Press investigation revealed.

Lenovo, HP and Dell, the nation's largest computer companies, have informed school districts that they are short nearly five million laptops.

[...] Last month, at the request of President Donald Trump, the U.S. Department of Commerce imposed sanctions on 11 Chinese companies, including Lenovo, AP reported. School administrators have asked the Trump administration to devise a solution because remote learning without laptops is impossible.

Lenovo has informed school districts of the supply chain delays and the trade controls set by the Commerce Department, which would cause another slowdown. Lenovo declined to respond to an inquiry from AP.

Have any Soylentils run into this?


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  • (Score: 2) by HiThere on Sunday August 30 2020, @08:36PM (3 children)

    by HiThere (866) Subscriber Badge on Sunday August 30 2020, @08:36PM (#1044327) Journal

    Ground rods won't stop sudden surges. They work fine for less sensitive gear. Possibly the problem is that surge suppressors wear out, or that you shouldn't have more than one of them between you and the main, or you get "echo surges". (Well, that's what I was told. I'm no hardware expert.)

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  • (Score: 2) by RS3 on Monday August 31 2020, @05:01AM (2 children)

    by RS3 (6367) on Monday August 31 2020, @05:01AM (#1044487)

    Ground rods won't stop sudden surges.

    Uh, I don't agree. They can certainly help a lot. I admit it all depends on where and how the surge is induced. But ground rods are meant to dissipate lightning and other big surges. I had buried copper phone lines and had several modems and phones badly damaged by surges until I finally installed 2 additional ground rods.

    The electric company's pole-mounted transformer that feeds my house has a big spark gap that every now and then would make a huge loud BOOM-BZZZZTTT sound- likely someone hitting a utility pole somewhere causing line shorts or downing wires. When that would happen our phones would jingle and uh-oh, things would be fried.

    Since adding the 2 ground rods maybe 10 years ago, that horrible sound has happened but nothing damaged, except 1 surge suppressor.

    More surge suppressors should be okay, but you need really good ground wiring and ground rods to give the surge somewhere to go.

    • (Score: 2) by HiThere on Monday August 31 2020, @01:46PM (1 child)

      by HiThere (866) Subscriber Badge on Monday August 31 2020, @01:46PM (#1044581) Journal

      Well, maybe I should have said spikes. And by sudden I'm talking about the kind of thing that wouldn't affect an incandescent light bulb, but will burn out typical printed capacitor. For slower changes they're a good answer, even if not full protection, but a transient spike will get through before the lightning arrester gets into action.

      That said, I'm depending on experts for this opinion. My own knowledge doesn't really cover this. My one experience with a lightning strike on the power lines left fragments of silicon spread out throughout the chassis of the computer, and the need for a total replacement. I suspect a ground rod would have prevented that.

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      • (Score: 4, Informative) by RS3 on Tuesday September 01 2020, @12:28AM

        by RS3 (6367) on Tuesday September 01 2020, @12:28AM (#1044771)

        I'm somewhat expert, but I don't deal exclusively with transients, etc. So it's not a simple thing to understand. For one, it depends on where the spike occurs- like in Joe's case, it probably came in mostly on the coax, and it wants go to a ground, so it went through the modem/gateway, which of course exploded, and along the Ethernets, taking out computers.

        But another and major factor is how much energy is in the spike. Also how tall (peak voltage) the spike is, but generally the more total energy in a spike, the higher the peak voltage.

        The actual working components of a surge suppressor are 1) spark gap, and 2) MOV (Metal Oxide Varistor). https://en.wikipedia.org/wiki/Varistor#:~:text=surge%20protector%20circuitry-,Hazards,this%20is%20not%20a%20problem. [wikipedia.org]

        Spark gaps aren't super useful by themselves for electronics- very high voltage occurs before they "spark over", and they're a bit slower than MOVs, so they're only used for certain things beyond the scope of this topic.

        MOVs are great, but as in one of the wiki pics, they can be destroyed during the surge, IE: lots of surge gets through after they clamp then explode. I've opened power strips and standalone surge suppressors inside of which the MOVs were blown apart. IE: nobody knew they had absorbed a surge and blew up in the process. Maybe a little window would allow inspection.

        And most of the common (cheap) surge suppressors use very small MOVs. But you can buy big MOVs to make a serious surge suppressor that will survive more surges, and overall clamp much more energy before they explode.

        For my phone's landline (being a tech / EE) I made a fairly simple surge suppressor consisting of some spark gaps (old special landline ones, tied to heavy wire tied to 3 ground rods), series resistors (to limit surge current), and more spark gaps. I've had to replace the series resistors a few times, showing that they did their jobs. I also cleaned the spark gaps- they're very precision and show "arc bites", which can have raised edges which can short out the lines, and a simple cleaning restores them. But the DSL modem survived many big surges.

        I haven't done one for AC mains yet, but fast-acting fuses before the MOV would also limit the total surge energy and its voltage spike.

        And an isolation transformer (1:1) would really protect things for AC mains spikes, but not for the lightning strike on the cable TV coax.

        Overall I agree with you, but my point is: every surge is different- in its duration time and its peak voltage. If you get a direct lightning strike on your house or power lines, all bets are off. There are no guarantees with this kind of thing.

        If lightening hits high-tension power lines, the transformer that brings that voltage down to 240 will dampen / absorb / spread out much of the spike, giving surge suppressors a chance.

        If the surge is due to high tension lines shorting (due to car hitting utility pole, for example) that might not be as high a peak voltage, but duration would be longer, so more total energy and MOVs explode and much of surge gets through.

        Power supplies can be built better. In (much) older PC power supplies I remember seeing MOVs, but most don't have them any more. Also, simply using higher voltage diodes and main power transistor would give better surge tolerance.

        The bottom line- it's not an exact science because surges don't follow the rules. :)