keyboard doesn't work, then does
in [Hardware]
|
From: mm on 13 Jul 2010 22:20 Keyboard doesn't work, then does WinXP Hi, I don't know what group would be best for this, but it's hardware related so I chose you. (I hope you feel honored.) Yesterday was a heavy rainstorm, no thunder that I recall, and no lighting that I saw out the window, but two very short power failures. One second each. I'm temporarily without a UPS. Everything else I've tried to use works, tv, radio, cordless telephone, speakers, fan, and in the other room DVDR, RF mod, TV, radio. The breaker in the bathroom tripped, a GFI breaker in the basement, but I'll bet the tv and radio connected to that still work fine. After each failure, the green light on the cmputer was flashing and neither pushing the reset button or the on/off button (for a moment or two) did anything. So I unplugged the cmputer, waited until the light stopped flashing, which took at least 5 seconds (why?) and plugged it in again. ******The second time, the PS-2 keyboard didn't work. No key afaict and in no program. I plugged in a USB keyboard and continued. After an hour or so I exited winXP, which turned off the computer. Later I restarted and again the PS-2 connected keyboard didn't work but the USB one did. (Unfortuately, the group of 6 keys are arranged differently. ugh.) Device manager said there was no problem with the keyboard. Later I exited and then started again and the third time the keyboard worked fine, everywhere, and has for the last 5 hours elapsed time. So what's going on? It seems like the keyboard is far away electrically from the power cord and the DSL line, too far to get damaged without the mobo being damaged, and anyhow, if it were damaged, how come it's working now? Any ideas? <sheepish grin>
From: Paul on 14 Jul 2010 00:11 mm wrote: > Keyboard doesn't work, then does WinXP > > Hi, > > I don't know what group would be best for this, but it's hardware > related so I chose you. (I hope you feel honored.) > > Yesterday was a heavy rainstorm, no thunder that I recall, and no > lighting that I saw out the window, but two very short power failures. > One second each. > > I'm temporarily without a UPS. > > Everything else I've tried to use works, tv, radio, cordless > telephone, speakers, fan, and in the other room DVDR, RF mod, TV, > radio. The breaker in the bathroom tripped, a GFI breaker in the > basement, but I'll bet the tv and radio connected to that still work > fine. > > After each failure, the green light on the cmputer was flashing and > neither pushing the reset button or the on/off button (for a moment or > two) did anything. So I unplugged the cmputer, waited until the > light stopped flashing, which took at least 5 seconds (why?) and > plugged it in again. > > ******The second time, the PS-2 keyboard didn't work. No key afaict > and in no program. I plugged in a USB keyboard and continued. After > an hour or so I exited winXP, which turned off the computer. > > Later I restarted and again the PS-2 connected keyboard didn't work > but the USB one did. (Unfortuately, the group of 6 keys are arranged > differently. ugh.) > > Device manager said there was no problem with the keyboard. > > Later I exited and then started again and the third time the keyboard > worked fine, everywhere, and has for the last 5 hours elapsed time. > > So what's going on? It seems like the keyboard is far away > electrically from the power cord and the DSL line, too far to get > damaged without the mobo being damaged, and anyhow, if it were > damaged, how come it's working now? > > Any ideas? <sheepish grin> I'll try the easy one first. "So I unplugged the computer, waited until the light stopped flashing, which took at least 5 seconds (why?) and plugged it in again." The light could be tied to +5VSB. The power supply has a large capacitor on the primary side, which holds a lot of energy. Part of the function of that capacitor, is to provide "hold up time" during a UPS switching event. The capacitor is guaranteed to hold up the supply for 16 milliseconds at full power supply load. In cases where only the +5VSB part of the supply is running, and the load on that rail isn't really that significant, the circuit can run for 30 seconds or longer, using juice stored in the capacitor. For more info, you can examine this schematic for an ATX PSU (C5 and C6 are the ones storing the energy - R2 and R3 are bleeder resistors, for making the capacitors "safe" when the unit is unplugged and opened up. Don't touch the terminals on the bottom of C5 and C6... ). http://www.pavouk.org/hw/en_atxps.html ******* Theorizing about your keyboard, would require the "purest speculation". I'm not sure I can make up a satisfying hypothesis for you. But I'll try relating a story. As a new designer at my first employer, I built a circuit, one of many modules used in a tall piece of equipment. I was getting complaints that my circuit was freezing (with some small probability of it happening). Most of the time, you'd plug my module in and it worked. But occasionally it would freeze and do nothing. I got a sample unit on my bench, and decided it would be fun to build an automated torture machine. I built a series of timers and relays, to turn the equipment on and off every 15 seconds, and evaluate whether it was working or not. The idea was, I could go home, and leave the equipment doing the tests all by itself. Sure enough, I caught the chip on the module, freezing. Power was there, but the chip would not do anything. I happened to stick the probe of my storage scope on the supply rail. The chip was supposed to run from a 5V supply. The scope recorded an 8 volt high transient when the power was turned on. Bingo! The high voltage of that transient, correlated with the freezing. It turned out, that as in every large engineering project, common infrastructure is designed by one engineer, and "given" to others. In this case, a filter network had been placed on *every* circuit pack (for reasons that were never fully explained). That filter was a "thing of its generation". I'd seen it used in some equipment I tore apart as a student, so I'd seen it before. It was an LC entry filter. My memory is foggy now, but I think my quick fix was to place a Zener after the filter, to clamp the amplitude of the overshoot, when the power comes on. No more freezes. I would have been happier to remove the damn filter, but the politics of the situation didn't make that possible. Something like that could happen to your keyboard, but then we'd have the messy detail, of trying to explain where a sharp-edged power transient would be coming from on the 5V feeding the keyboard. That is the part of the hypothesis that doesn't make sense. We'd also need to open the keyboard, and see whether an ancient LC filter was at play or not. I doubt you're going to have this happen again, so it would be pretty hard to prove or disprove what happened. At minimum, anyone studying this, would need to start by opening up the keyboard, and seeing how it was designed. Another mechanism to "freeze" a circuit, is latchup (or micro-latchup). I've seen micro-latchup first hand, and at 4PM in the afternoon, I thought my circuit was dead. Turned off the power and went home. At 8AM the next morning, I turned on the power and it was working again. I couldn't believe it, because I thought I'd fried an expensive and valuable chip (we only had 25 prototypes at the time). There was a solid technical reason for that happening, and I had a solution in hand in a day or two, to stop it. But finding a solution wouldn't have happened, without noting that the chip recovered from its failure. That was the clue I needed, to focus my search in the right direction. In the case of your keyboard, I'd be hard pressed to relate such a mechanism to the keyboard controller. But it is another phenomenon that can freeze circuits, and requires that all the stray charge be drained out of the circuit before it will recover. http://en.wikipedia.org/wiki/Latchup Paul
From: philo on 14 Jul 2010 06:50 On 07/13/2010 09:20 PM, mm wrote: > > Keyboard doesn't work, then does WinXP > > Hi, > > I don't know what group would be best for this, but it's hardware > related so I chose you. (I hope you feel honored.) > > Yesterday was a heavy rainstorm, no thunder that I recall, and no > lighting that I saw out the window, but two very short power failures. > One second each. > > I'm temporarily without a UPS. > > Everything else I've tried to use works, tv, radio, cordless > telephone, speakers, fan, and in the other room DVDR, RF mod, TV, > radio. The breaker in the bathroom tripped, a GFI breaker in the > basement, but I'll bet the tv and radio connected to that still work > fine. > > After each failure, the green light on the cmputer was flashing and > neither pushing the reset button or the on/off button (for a moment or > two) did anything. So I unplugged the cmputer, waited until the > light stopped flashing, which took at least 5 seconds (why?) and > plugged it in again. > > ******The second time, the PS-2 keyboard didn't work. No key afaict > and in no program. I plugged in a USB keyboard and continued. After > an hour or so I exited winXP, which turned off the computer. > > Later I restarted and again the PS-2 connected keyboard didn't work > but the USB one did. (Unfortuately, the group of 6 keys are arranged > differently. ugh.) > > Device manager said there was no problem with the keyboard. > > Later I exited and then started again and the third time the keyboard > worked fine, everywhere, and has for the last 5 hours elapsed time. > > So what's going on? It seems like the keyboard is far away > electrically from the power cord and the DSL line, too far to get > damaged without the mobo being damaged, and anyhow, if it were > damaged, how come it's working now? > > Any ideas?<sheepish grin> I've seen that many times With the machine *off* unplug the keyboard then plug it back in and make sure it is fully inserted. If that does not solve the problem then try another ps/2 keyboard
From: mm on 14 Jul 2010 15:06 On Wed, 14 Jul 2010 00:11:32 -0400, Paul <nospam(a)needed.com> wrote: >mm wrote: >> Keyboard doesn't work, then does WinXP >> >> Hi, >> >> I don't know what group would be best for this, but it's hardware >> related so I chose you. (I hope you feel honored.) >> >> Yesterday was a heavy rainstorm, no thunder that I recall, and no >> lighting that I saw out the window, but two very short power failures. >> One second each. >> >> I'm temporarily without a UPS. >> >> Everything else I've tried to use works, tv, radio, cordless >> telephone, speakers, fan, and in the other room DVDR, RF mod, TV, >> radio. The breaker in the bathroom tripped, a GFI breaker in the >> basement, but I'll bet the tv and radio connected to that still work >> fine. >> >> After each failure, the green light on the cmputer was flashing and >> neither pushing the reset button or the on/off button (for a moment or >> two) did anything. So I unplugged the cmputer, waited until the >> light stopped flashing, which took at least 5 seconds (why?) and >> plugged it in again. >> >> ******The second time, the PS-2 keyboard didn't work. No key afaict >> and in no program. I plugged in a USB keyboard and continued. After >> an hour or so I exited winXP, which turned off the computer. >> >> Later I restarted and again the PS-2 connected keyboard didn't work >> but the USB one did. (Unfortuately, the group of 6 keys are arranged >> differently. ugh.) >> >> Device manager said there was no problem with the keyboard. >> >> Later I exited and then started again and the third time the keyboard >> worked fine, everywhere, and has for the last 5 hours elapsed time. >> >> So what's going on? It seems like the keyboard is far away >> electrically from the power cord and the DSL line, too far to get >> damaged without the mobo being damaged, and anyhow, if it were >> damaged, how come it's working now? >> >> Any ideas? <sheepish grin> > >I'll try the easy one first. > > "So I unplugged the computer, waited until the light stopped flashing, > which took at least 5 seconds (why?) and plugged it in again." > >The light could be tied to +5VSB. The power supply has a large capacitor >on the primary side, which holds a lot of energy. Part of the function >of that capacitor, is to provide "hold up time" during a UPS switching >event. The capacitor is guaranteed to hold up the supply for 16 milliseconds >at full power supply load. In cases where only the +5VSB part of the >supply is running, and the load on that rail isn't really that significant, >the circuit can run for 30 seconds or longer, using juice stored in the >capacitor. For more info, you can examine this schematic for an ATX PSU >(C5 and C6 are the ones storing the energy - R2 and R3 are bleeder resistors, >for making the capacitors "safe" when the unit is unplugged and opened up. >Don't touch the terminals on the bottom of C5 and C6... ). This makes sense. >http://www.pavouk.org/hw/en_atxps.html Thanks. >******* > >Theorizing about your keyboard, would require the "purest speculation". Isn't that the best kind of speculation? IIRC it's the best kind of orange juice. >I'm not sure I can make up a satisfying hypothesis for you. But I'll try >relating a story. > >As a new designer at my first employer, I built a circuit, one of many >modules used in a tall piece of equipment. I was getting complaints that >my circuit was freezing (with some small probability of it happening). >Most of the time, you'd plug my module in and it worked. But occasionally >it would freeze and do nothing. > >I got a sample unit on my bench, and decided it would be fun to build an >automated torture machine. I built a series of timers and relays, to turn >the equipment on and off every 15 seconds, and evaluate whether it was >working or not. The idea was, I could go home, and leave the equipment doing >the tests all by itself. > >Sure enough, I caught the chip on the module, freezing. Power was there, >but the chip would not do anything. > >I happened to stick the probe of my storage scope on the supply rail. The chip >was supposed to run from a 5V supply. The scope recorded an 8 volt high transient >when the power was turned on. Bingo! The high voltage of that transient, >correlated with the freezing. > >It turned out, that as in every large engineering project, common infrastructure >is designed by one engineer, and "given" to others. In this case, a filter >network had been placed on *every* circuit pack (for reasons that were never >fully explained). That filter was a "thing of its generation". I'd seen >it used in some equipment I tore apart as a student, so I'd seen it before. >It was an LC entry filter. > >My memory is foggy now, but I think my quick fix was to place a Zener after >the filter, to clamp the amplitude of the overshoot, when the power comes >on. No more freezes. I would have been happier to remove the damn filter, >but the politics of the situation didn't make that possible. > >Something like that could happen to your keyboard, but then we'd have the >messy detail, of trying to explain where a sharp-edged power transient would be >coming from on the 5V feeding the keyboard. That is the part of the hypothesis >that doesn't make sense. We'd also need to open the keyboard, and see whether >an ancient LC filter was at play or not. > >I doubt you're going to have this happen again, so it would be >pretty hard to prove or disprove what happened. At minimum, anyone >studying this, would need to start by opening up the keyboard, >and seeing how it was designed. > >Another mechanism to "freeze" a circuit, is latchup (or micro-latchup). >I've seen micro-latchup first hand, and at 4PM in the afternoon, I >thought my circuit was dead. Turned off the power and went home. At >8AM the next morning, I turned on the power and it was working again. >I couldn't believe it, because I thought I'd fried an expensive >and valuable chip (we only had 25 prototypes at the time). There was a >solid technical reason for that happening, and I had a solution in hand >in a day or two, to stop it. But finding a solution wouldn't have happened, >without noting that the chip recovered from its failure. That was the >clue I needed, to focus my search in the right direction. In the case >of your keyboard, I'd be hard pressed to relate such a mechanism to >the keyboard controller. But it is another phenomenon that can freeze >circuits, and requires that all the stray charge be drained out of the >circuit before it will recover. > >http://en.wikipedia.org/wiki/Latchup Thanks for all this. very interesting. I used to buy keyboards at hamfests for a dollar each, but now I like the ones with volume control, etc. and they are two dollars each when I find them. So this is just a curiosity, but I'm a very curious guy. I'll read the webpages you give too. FTR, it's a Microsoft keyboard with 16 extra buttons at the top. I don't see a model number. Thanks, Philo, also. > Paul
From: mm on 29 Jul 2010 21:01 Well, the keyboard that didn't work right has been working fine for two weeks now. Except all of a sudden for a five-minute period where the shift seemed to be on all the time, even for characters like period and comma, which came out like < and >. Some keys didn't work at all. I plugged in the USB keyboard and it worked like that too. But after a couple minutes of pressing keys and trying different programs, it went back to normal, and that was 5 days ago. Life is strange. Thanks again for your help. On Tue, 13 Jul 2010 22:20:00 -0400, mm <NOPSAMmm2005(a)bigfoot.com> wrote: > >Keyboard doesn't work, then does WinXP > >Hi, > >I don't know what group would be best for this, but it's hardware >related so I chose you. (I hope you feel honored.) > >Yesterday was a heavy rainstorm, no thunder that I recall, and no >lighting that I saw out the window, but two very short power failures. >One second each. > >I'm temporarily without a UPS. > >Everything else I've tried to use works, tv, radio, cordless >telephone, speakers, fan, and in the other room DVDR, RF mod, TV, >radio. The breaker in the bathroom tripped, a GFI breaker in the >basement, but I'll bet the tv and radio connected to that still work >fine. > >After each failure, the green light on the cmputer was flashing and >neither pushing the reset button or the on/off button (for a moment or >two) did anything. So I unplugged the cmputer, waited until the >light stopped flashing, which took at least 5 seconds (why?) and >plugged it in again. > >******The second time, the PS-2 keyboard didn't work. No key afaict >and in no program. I plugged in a USB keyboard and continued. After >an hour or so I exited winXP, which turned off the computer. > >Later I restarted and again the PS-2 connected keyboard didn't work >but the USB one did. (Unfortuately, the group of 6 keys are arranged >differently. ugh.) > >Device manager said there was no problem with the keyboard. > >Later I exited and then started again and the third time the keyboard >worked fine, everywhere, and has for the last 5 hours elapsed time. > >So what's going on? It seems like the keyboard is far away >electrically from the power cord and the DSL line, too far to get >damaged without the mobo being damaged, and anyhow, if it were >damaged, how come it's working now? > >Any ideas? <sheepish grin>
|
Pages: 1 Prev: Which Audio spec ? Next: Options for connecting two computers with USB? |