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dead USB ports too frequent for my liking
I have had 20 PCs since USB came out, and at least half of them had 1
dead USB port after a while. In only one case could I see bent contacts in the socket. So I wonder is this the usual problem, or do the USB chips get zapped? I presume the sockets 5 V pins are fed from a common rail, so it would be the data lines that died. |
#2
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dead USB ports too frequent for my liking
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#3
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dead USB ports too frequent for my liking
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#5
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dead USB ports too frequent for my liking
On Sun, 14 Jun 2015 10:10:46 -0400, Larc wrote:
I connect front panel ports to use for USB flash drives and such and have never had one of those fail. Neither have I. An uncle of mine /did/, but I haven't encountered in on other PCs. -- s|b |
#6
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dead USB ports too frequent for my liking
On 14 Jun 2015, "s|b" wrote in
alt.comp.hardware.pc-homebuilt: On Sun, 14 Jun 2015 10:10:46 -0400, Larc wrote: I connect front panel ports to use for USB flash drives and such and have never had one of those fail. Neither have I. An uncle of mine /did/, but I haven't encountered in on other PCs. There's no real reason the front ones should fail any more often than the rear ones, except that they're more exposed to being knocked around. USB connectors are a bad design in the first place and they don't resist physical abuse very well. |
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dead USB ports too frequent for my liking
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#8
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dead USB ports too frequent for my liking
Nil wrote:
On 14 Jun 2015, "s|b" wrote in alt.comp.hardware.pc-homebuilt: On Sun, 14 Jun 2015 10:10:46 -0400, Larc wrote: I connect front panel ports to use for USB flash drives and such and have never had one of those fail. Neither have I. An uncle of mine /did/, but I haven't encountered in on other PCs. There's no real reason the front ones should fail any more often than the rear ones, except that they're more exposed to being knocked around. USB connectors are a bad design in the first place and they don't resist physical abuse very well. There is a reason, but I didn't want to write it up. It has to do with the plastic front on the computer. When you dump ESD into a front panel USB, it can't "drain" into the chassis directly. The ESD discharge goes down the front panel USB cable, down the ground of it. And while doing so, the wire is in parallel with D+ and D-, inducing high voltage in those leads too. Whereas the rear connectors are beautifully designed. The area around the connector has metal, the metal makes contact with the chassis. The spring fingers on the I/O plate, provide a conduction path between the chassis and the connector body. The "parallel" run of wires in that case, is very short. If you're lucky enough to have a PC with a metal fascia on the front, then there would be an opportunity for some of the ESD energy to go into the chassis, instead of near the wires. Using plastic on the front of the machine, allows the manufacturer to make complex aesthetically pleasing shapes with minimal work. If the front was fabricated out of metal, the box would likely look more ugly that it already is. ESD protection for equipment is a complex subject. Some designers, their first approach is to insulate everything on the front, if possible. (So the user can't zap anything.) If you're putting I/O connectors on a surface, that idea is ruined right away. The next approach after that, is to "drain" to chassis. Even this can be problematic in terms of upset. We had a system, where every time there was the least contact between computer metal and metal chairs or objects in the room, the box would reset. And there was an actual reset wire inside the computer, picking up energy by induction. Once that was improved, the problem stopped. I got a free plane flight to a customer site, to observe that one happening, and it was plenty freaky. The amount of signal required to upset the computer was amazingly small. You could fart, and that computer design would reset itself, and all because some clever person left a long run of reset wire (no twisted pair) inside the box. We test systems like that at work, with an ESD probe modeling the Human Body Model. It includes an RC time constant, and you charge to "X" volts and do your test. The equipment will have "upset" and "damage" ratings, at two different voltages. So maybe the spec says it cannot reset if hit with 5kV of discharge, or it cannot be damaged if hit with 10kV. The probe has an insulated handle, and a rounded tip to avoid corona. And then you bring it up to the equipment and zap it, and test whether your protection design is working. We had *many* failures with the "metal draining" method, requiring analysis of where the discharge was going. In some cases, spring fingers being added to some metal things, to encourage high voltage discharge to go down a certain path. I never had to get involved in that stuff for what I was building (never ran the HV probe myself), but I was around while the other staff were working on it (multiple projects). So got to discuss the approach they were using. Fun stuff. And we never had incidents of staff zapping one another with the probe. True professionals :-) Just to prove the probe was actually modeling HBM, and gave a human amount of static-like discharge. Intel USB ports are rated for around 5-6kV of ESD (written up in the Intel Journal). RS232 ports (good ones), are rated for 15kV, and those were the first chips to be recognized as having a problem, and the redesign of those was excellent. Regular chips (where the wires don't go near humans) are rated for 1kV or so. For third party USB, like NEC brand, I have no idea what their rating is, but it's probably not as high as Intel. Some PCI Express slots are extremely sensitive, and could well be 1kV or less (there were some early PCI Express designs, where customers blew out the PCI Express slot during their equipment build). On those systems, once alerted to that fact, you'd want your ESD strap while assembling computers based on those boards. Since I'm no longer hearing that complaint, I guess the chipset makers have figured that out. It's possible to add protection networks to electrical items externally. But this topic is more art than science, and the vast majority of available solutions for it are crap. I worked with a gentleman, who tirelessly tested this stuff. Even when not tasked with a design, he would get samples of components like this and test them. The critical parameter is stray capacitance, and good components (1pF or less) are hard to find. Some of the good solutions, were coming from small companies (startups), and not from the larger suppliers. You cannot put these on high speed signals, unless the stray capacitance is extremely low. Which rules out most of the ones you see advertised. http://www.eetimes.com/document.asp?doc_id=1275127 Paul |
#9
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dead USB ports too frequent for my liking
On Sunday, June 14, 2015 at 10:51:19 PM UTC+8, Mr. Man-wai Chang wrote:
Are they branded PCs? What brand? A few were HP or Dell. Mostly they were small PC shop jobs: Intel, Asus or Gigabyte boards in Antec, Coolermaster or Thermaltake case. I have 2 cases with metal fronts: Silverstone and LIANLI. The LIANLI has a dud USB port, the Silverstone has been trouble free. |
#10
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dead USB ports too frequent for my liking
On 14/6/15 11:59 AM, wrote:
I have had 20 PCs since USB came out, and at least half of them had 1 dead USB port after a while. In only one case could I see bent contacts in the socket. So I wonder is this the usual problem, or do the USB chips get zapped? I have never fried a USB port before, NOT ONCE. But then my PC is not in public space. -- @~@ Remain silent. Nothing from soldiers and magicians is real! / v \ Simplicity is Beauty! May the Force and farces be with you! /( _ )\ (Fedora release 21) Linux 4.0.4-202.fc21.i686+PAE ^ ^ 23:09:01 up 7 days 19:57 0 users load average: 0.00 0.01 0.05 不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA): http://www.swd.gov.hk/tc/index/site_...sub_addressesa |
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