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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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USB port blew -- why?
One of the ports of my NEC-based USB 2.0 card quit working because the
National Semiconductor LM3526 power controller chip failed. I'm pretty sure that I didn't zap it with static (I always touch the outher metal shell to the computer case before plugging it in) or try to plug it in backwards. The data sheet for the LM3526 says that it's protected against voltage, current, and even temperature, so what happened? National Semiconductor says that each USB port must have a 120uF or larger tantalum capacitor between +5V and ground for protection against transients that occur during hot-plugging, and NEC's example schematic for their uPD720100A USB 2.0 chip shows the LM3526 using 150uF aluminum in parallel with 0.1uF ceramic. But my USB card has only a 100uF aluminum capacitor and maybe a ceramic capacitor in parallel for this. Could this be why the USB port got zapped? Would it help to solder a tantalum in parallel as well? Will it hurt to add it? |
#2
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"larrymoencurly" wrote in message om... .... | National Semiconductor says that each USB port must have a 120uF or | larger ....................................... But my USB card has | only a 100uF aluminum capacitor and maybe a ceramic capacitor in | parallel for this.... Close enough! N |
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On Mon, 04 Oct 2004 01:50:54 GMT, "NSM" wrote:
"larrymoencurly" wrote in message . com... ... | National Semiconductor says that each USB port must have a 120uF or | larger ....................................... But my USB card has | only a 100uF aluminum capacitor and maybe a ceramic capacitor in | parallel for this.... Close enough! Except the tantalum cap would have much lower esl & esr figures than an aluminum cap, making it more effective. otoh, tantalums can have a brilliant failure mode ;-) |
#4
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On Mon, 04 Oct 2004 03:21:58 +0000, daytripper wrote:
On Mon, 04 Oct 2004 01:50:54 GMT, "NSM" wrote: "larrymoencurly" wrote in message .com... ... | National Semiconductor says that each USB port must have a 120uF or | larger ....................................... But my USB card has | only a 100uF aluminum capacitor and maybe a ceramic capacitor in | parallel for this.... Close enough! Except the tantalum cap would have much lower esl & esr figures than an aluminum cap, making it more effective. otoh, tantalums can have a brilliant failure mode ;-) So do engineers when they're bringing up a system where all of the tantallums were inserted backwards. You want to see fireworks! (well,it was 25 years ago - I've mostly recovered and the tinninus isn't so bad. twitch) -- Keith |
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keith wrote:
On Mon, 04 Oct 2004 03:21:58 +0000, daytripper wrote: On Mon, 04 Oct 2004 01:50:54 GMT, "NSM" wrote: "larrymoencurly" wrote in message e.com... ... | National Semiconductor says that each USB port must have a 120uF or | larger ....................................... But my USB card has | only a 100uF aluminum capacitor and maybe a ceramic capacitor in | parallel for this.... Close enough! Except the tantalum cap would have much lower esl & esr figures than an aluminum cap, making it more effective. otoh, tantalums can have a brilliant failure mode ;-) So do engineers when they're bringing up a system where all of the tantallums were inserted backwards. You want to see fireworks! (well,it was 25 years ago - I've mostly recovered and the tinninus isn't so bad. twitch) LOL. Yeah, I'll bet. You get a similar result plugging non keyed circuit boards into a vertical card rack 180 degrees reversed. |
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On Mon, 04 Oct 2004 22:33:31 -0500, David Maynard wrote:
keith wrote: On Mon, 04 Oct 2004 03:21:58 +0000, daytripper wrote: On Mon, 04 Oct 2004 01:50:54 GMT, "NSM" wrote: "larrymoencurly" wrote in message le.com... ... | National Semiconductor says that each USB port must have a 120uF or | larger ....................................... But my USB card has | only a 100uF aluminum capacitor and maybe a ceramic capacitor in | parallel for this.... Close enough! Except the tantalum cap would have much lower esl & esr figures than an aluminum cap, making it more effective. otoh, tantalums can have a brilliant failure mode ;-) So do engineers when they're bringing up a system where all of the tantallums were inserted backwards. You want to see fireworks! (well,it was 25 years ago - I've mostly recovered and the tinninus isn't so bad. twitch) LOL. Yeah, I'll bet. You get a similar result plugging non keyed circuit boards into a vertical card rack 180 degrees reversed. A good reason to hang the mechanical designers by the short things. One *should* have to go to great lengths to pluch dangerous things in backwards. In this case they did just that. ...and even complained about how hard it was! -- Keith |
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"keith" wrote in message news | So do engineers when they're bringing up a system where all | of the tantallums were inserted backwards. You want to see fireworks! | (well,it was 25 years ago - I've mostly recovered and the tinninus | isn't so bad. twitch) I recall being told of a large TTL circuit board which was powered up with reverse polarity. This was noticed due to the considerable amount of heat being given off. Everyone was mystified when the correctly rewired board worked OK. I guess TTL is a little more tolerant than is generally believed. N |
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On Tue, 05 Oct 2004 03:47:13 +0000, NSM wrote:
"keith" wrote in message news | So do engineers when they're bringing up a system where all | of the tantallums were inserted backwards. You want to see fireworks! | (well,it was 25 years ago - I've mostly recovered and the tinninus | isn't so bad. twitch) I recall being told of a large TTL circuit board which was powered up with reverse polarity. This was noticed due to the considerable amount of heat being given off. Everyone was mystified when the correctly rewired board worked OK. I guess TTL is a little more tolerant than is generally believed. TTL protection diodes are as strong as moose! Unless the chips got hot enough to let the magic smoke out, they'll likely survive, though perhaps somewhat injured. -- Keith |
#9
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"larrymoencurly" wrote in message om... One of the ports of my NEC-based USB 2.0 card quit working because the National Semiconductor LM3526 power controller chip failed. I'm pretty sure that I didn't zap it with static (I always touch the outher metal shell to the computer case before plugging it in) or try to plug it in backwards. The data sheet for the LM3526 says that it's protected against voltage, current, and even temperature, so what happened? Stuff just fails occasionally with no good explaination, could be it was just a defective part that eventually quit. |
#10
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"James Sweet" wrote in message news:lu58d.2427$r3.597@trnddc05... | | "larrymoencurly" wrote in message | om... | One of the ports of my NEC-based USB 2.0 card quit working because the | National Semiconductor LM3526 power controller chip failed. I'm | pretty sure that I didn't zap it with static (I always touch the | outher metal shell to the computer case before plugging it in) or try | to plug it in backwards. The data sheet for the LM3526 says that it's | protected against voltage, current, and even temperature, so what | happened? | | | Stuff just fails occasionally with no good explaination, could be it was | just a defective part that eventually quit. Or as I say, "Everything works until it breaks". Then there are the three brand new tubes I took off the shelf one at a time, each of which was bad. Still can't get over that one. N |
#11
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NSM wrote:
"James Sweet" wrote in message news:lu58d.2427$r3.597@trnddc05... | | "larrymoencurly" wrote in message | om... | One of the ports of my NEC-based USB 2.0 card quit working because the | National Semiconductor LM3526 power controller chip failed. I'm | pretty sure that I didn't zap it with static (I always touch the | outher metal shell to the computer case before plugging it in) or try | to plug it in backwards. The data sheet for the LM3526 says that it's | protected against voltage, current, and even temperature, so what | happened? | | | Stuff just fails occasionally with no good explaination, could be it was | just a defective part that eventually quit. Or as I say, "Everything works until it breaks". HEY!! That's MY line. Then there are the three brand new tubes I took off the shelf one at a time, each of which was bad. Still can't get over that one. Find the guy who put the defective ones back on the shelf g. N |
#12
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"James Sweet" wrote in message news:lu58d.2427$r3.597@trnddc05...
Stuff just fails occasionally with no good explaination, could be it was just a defective part that eventually quit. I am eternally grateful for your answer, which not only completely solved my problem with the USB port but will also magically turn the rest of my life into bliss. So please give me your address so that I can send you a $500 check, no, make that a blank check -- your advice was that good. |
#13
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#14
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forgive me for not immediately recommending you open the controller chip and
place it under your scanning electron microscope to search for signs of electromigration... "larrymoencurly" wrote in message om... "James Sweet" wrote in message news:lu58d.2427$r3.597@trnddc05... Stuff just fails occasionally with no good explaination, could be it was just a defective part that eventually quit. I am eternally grateful for your answer, which not only completely solved my problem with the USB port but will also magically turn the rest of my life into bliss. So please give me your address so that I can send you a $500 check, no, make that a blank check -- your advice was that good. |
#15
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"larrymoencurly" wrote in message om... "James Sweet" wrote in message news:lu58d.2427$r3.597@trnddc05... Stuff just fails occasionally with no good explaination, could be it was just a defective part that eventually quit. I am eternally grateful for your answer, which not only completely solved my problem with the USB port but will also magically turn the rest of my life into bliss. So please give me your address so that I can send you a $500 check, no, make that a blank check -- your advice was that good. Just what sort of answer did you expect? I seem to have misplaced my crystal ball and I can't find my spell book either. How is anyone supposed to tell you why a chip failed? It just happens. |
#16
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"larrymoencurly" wrote in message om... | "James Sweet" wrote in message news:lu58d.2427$r3.597@trnddc05... | | Stuff just fails occasionally with no good explaination, could be | it was just a defective part that eventually quit. | | I am eternally grateful for your answer, which not only completely | solved my problem with the USB port but will also magically turn the | rest of my life into bliss. So please give me your address so that I | can send you a $500 check, no, make that a blank check -- your advice | was that good. Assuming you are being sarcastic (it's not clear), I refer to this as a CatRan question, i.e., "I was typing away on my computer and I was holding the keyboard above my head and I was watching the screen through my toes when all of a sudden the cat ran over my stomach and I noticed the screen blinked twice. What causes that"? N |
#17
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"NSM" wrote in news:sgI8d.14605$MV5.538@clgrps13:
"larrymoencurly" wrote in message om... | "James Sweet" wrote in message news:lu58d.2427$r3.597@trnddc05... | | Stuff just fails occasionally with no good explaination, could be | it was just a defective part that eventually quit. | | I am eternally grateful for your answer, which not only completely | solved my problem with the USB port but will also magically turn the | rest of my life into bliss. So please give me your address so that I | can send you a $500 check, no, make that a blank check -- your advice | was that good. Assuming you are being sarcastic (it's not clear), I refer to this as a CatRan question, i.e., "I was typing away on my computer and I was holding the keyboard above my head and I was watching the screen through my toes when all of a sudden the cat ran over my stomach and I noticed the screen blinked twice. What causes that"? N Reminds me of the time an aquaintance went to lunch with me and a few of the other engineers. He was in a rather "know it all" mood. I started plying him with questions about how water softeners work, what causes gravity, etc. He was doing good until I asked him, "Ever wake up on a wednesday and think it was tuesday all day and then wake up the next day and everything is ok again? What is that called?" He shut up after that. r -- Nothing beats the bandwidth of a station wagon filled with DLT tapes. |
#18
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Rich.Andrews wrote:
Reminds me of the time an aquaintance went to lunch with me and a few of the other engineers. He was in a rather "know it all" mood. I started plying him with questions about how water softeners work, what causes gravity, etc. He was doing good until I asked him, "Ever wake up on a wednesday and think it was tuesday all day and then wake up the next day and everything is ok again? What is that called?" He shut up after that. Groundhog day? |
#19
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"Rich.Andrews" wrote in message .1...
Assuming you are being sarcastic (it's not clear), The "" always means non-hostile sarcasm. I refer to this as a CatRan question, i.e., "I was typing away on my computer and I was holding the keyboard above my head and I was watching the screen through my toes when all of a sudden the cat ran over my stomach and I noticed the screen blinked twice. What causes that"? I think that it's more like, why did the waterproof flashlight suddenly stop working when it started to rain? |
#20
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what main board? FIC ECS MSI?...usb blew cause the board blows.
"larrymoencurly" wrote in message om... One of the ports of my NEC-based USB 2.0 card quit working because the National Semiconductor LM3526 power controller chip failed. I'm pretty sure that I didn't zap it with static (I always touch the outher metal shell to the computer case before plugging it in) or try to plug it in backwards. The data sheet for the LM3526 says that it's protected against voltage, current, and even temperature, so what happened? National Semiconductor says that each USB port must have a 120uF or larger tantalum capacitor between +5V and ground for protection against transients that occur during hot-plugging, and NEC's example schematic for their uPD720100A USB 2.0 chip shows the LM3526 using 150uF aluminum in parallel with 0.1uF ceramic. But my USB card has only a 100uF aluminum capacitor and maybe a ceramic capacitor in parallel for this. Could this be why the USB port got zapped? Would it help to solder a tantalum in parallel as well? Will it hurt to add it? |
#21
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"JAD" wrote in message ...
"larrymoencurly" wrote in message om... One of the ports of my NEC-based USB 2.0 card quit working because the National Semiconductor LM3526 power controller chip failed. I'm pretty sure that I didn't zap it with static or try to plug it in backwards. The data sheet for the LM3526 says that it's protected against voltage, current, and even temperature, so what happened? National Semiconductor says that each USB port must have a 120uF or larger tantalum capacitor between +5V and ground for protection against transients that occur during hot-plugging, and NEC's example schematic for their uPD720100A USB 2.0 chip shows the LM3526 using 150uF aluminum in parallel with 0.1uF ceramic. But my USB card has only a 100uF aluminum capacitor and maybe a ceramic capacitor in parallel for this. Could this be why the USB port got zapped? Would it help to solder a tantalum in parallel as well? Will it hurt? what main board? FIC ECS MSI?...usb blew cause the board blows. My main boards are cheap, FIC and ECS, so any built-in USB for them uses an SiS or VIA chip. My NEC USB is a PCI card. But why couldn't any built-in USB blow out because of something off the main board? I had a built-in RS-232 serial port blow because someone tried to hot plug a parallel printer port (vaporized a couple of tiny capacitors used by the RS-232-TTL converter chip), no other damage. |
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