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#1
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WinXP keeps not seeing USB connected external hard drive.
I have an unusual problem. Some time ago, I got a USB connected 250G
external hard drive that I use only for storage. My WinXP system has got so used to it that it thinks it's a regular hard drive instead of "removeable media." The problem is that here in the past few months, my system randomly decides that the drive isn't there at all as if it's unplugged. Any Windows Explorer window showing any folder on the drive closes. Any program such as a web browser that last saved something to that drive goes to the default folder on the main drive if I try to save something. If eMule is running, any file that's downloading gets a "error" and my comp gives an error beep. If Visipics (duplicate image detector) is running, it thinks the job is done. To restore the connection, usually, I unplug the connector from the USB port and plug it back in. Sometimes I have to restart my system. The external HD I have now is a HP Pocket Drive that's entirely USB powered. I suspect that if I were still using the Lasonic 250G USB connected drive that required an external power source, the problem would still be happening. Once in awhile, the same type thing happens to my mouse and keyboard, both of which are connected to the USB port next to the external HD's port through a USB hub. They quit working or proper operation is spotty. Proper operation is restored through unplugging the hub and plugging it back in and once in awhile, a restart is required. Anyone have any idea of what's causing this, how to fix it and how to prevent it? |
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#2
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WinXP keeps not seeing USB connected external hard drive.
Moonbarker Osbourne wrote:
I have an unusual problem. Some time ago, I got a USB connected 250G external hard drive that I use only for storage. My WinXP system has got so used to it that it thinks it's a regular hard drive instead of "removeable media." As I recall, it has to do with how the external controller reports its capabilities to the OS. Don't think XP can "get used to" anything. The problem is that here in the past few months, my system randomly decides that the drive isn't there at all as if it's unplugged. Any Windows Explorer window showing any folder on the drive closes. Any program such as a web browser that last saved something to that drive goes to the default folder on the main drive if I try to save something. If eMule is running, any file that's downloading gets a "error" and my comp gives an error beep. If Visipics (duplicate image detector) is running, it thinks the job is done. To restore the connection, usually, I unplug the connector from the USB port and plug it back in. Sometimes I have to restart my system. The external HD I have now is a HP Pocket Drive that's entirely USB powered. I suspect that if I were still using the Lasonic 250G USB connected drive that required an external power source, the problem would still be happening. Once in awhile, the same type thing happens to my mouse and keyboard, both of which are connected to the USB port next to the external HD's port through a USB hub. They quit working or proper operation is spotty. Proper operation is restored through unplugging the hub and plugging it back in and once in awhile, a restart is required. Anyone have any idea of what's causing this, how to fix it and how to prevent it? USB hard drives are marginal at best. You start out with 5Volts, but there are current sense resistors, PTC "fuses", wire losses etc that all add up to "almost enough voltage left to reliably run the drive. Assuming you're using high-power USB2 ports, the current limit is 500mA. And big hard drives easily peak at more than that. If your drive came with a splitter to run it from two ports, you know why. If it didn't, some marketing guy probably decided it would be "ok". You can look in device manager to see what the drive reports as required power...but that isn't helpful. It probably won't ever say that it exceeds the limit or it wouldn't get certified. I have one external drive that draws 800mA. Never got it to run directly from the port, so can't say what the port thinks the load would be. Implementation varies all over the map. There's often a current sense internal to the chip that shuts down the port when you draw too much current. Some just limit the current and let the volts droop. That's very bad for your data. Some cut out completely and reset when you remove the load. I've got one laptop that cuts out and doesn't come back until I power off the system. I have another that gives an overload message when you plug in the drive, but lets it run anyway. Then there's the PTC thermal fuse that protects the chip against shorts. It drops some voltage. Overload heats it up, until it gets hot enough to cause a dramatic increase in resistance. You have to cut the load and let it cool to reset. Something as simple as dust on the PTC can insulate it and cause the trip-current to decrease. Increase in temperature internal to the computer box can send an already marginal system over the edge. If you look at the spec for the PTC fuse, you find that the initial specified cold resistance is several times lower than the cold resistance after it's tripped once. So, the longer it runs hot, the worse it gets. The worse it gets, the hotter it runs...you can't catch a break. To solve a laptop problem, I did some surgery on the docking station USB1.1 port. I put another PTC fuse between the keyboard 5V and the USB port. Now the port can drive my external HD. If it's the PTC, you can switch ports to see if that helps...until that one degrades... Another problem is cable resistance. Make sure you're using a Qualified USB2 cable with bigger power wires. And as short as possible. A powered hub can solve your problem, but it can introduce other issues with the hub. If the hub has a switch for external power, you get all the volts. Some "auto switch", which means they have diodes that drop the voltage another .35V or so. I have a usb/IDE adapter that works that way. Finally had to put a jumper across the diode to make it reliable. But that causes other problems. When you power off the computer, the drive supply goes back thru the USB port and tries to run the computer. Can cause some very strange symptoms. I gave up on USB powered hard drives. I kept my older external boxes that allow external power for the drive. And I tapped into an extension cable to supply power to my drives that can't do external power. Are we having fun yet? mike |
#3
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WinXP keeps not seeing USB connected external hard drive.
"spamme0" wrote:
As I recall, it has to do with how the external controller reports its capabilities to the OS. Don't think XP can "get used to" anything. Ah, OK! Assuming you're using high-power USB2 ports, the current limit is 500mA. That's what I'm using. And big hard drives easily peak at more than that. If your drive came with a splitter to run it from two ports, you know why. If it didn't, some marketing guy probably decided it would be "ok". Mine did come with a splitter. In gooogling "hp pocket media drive power requirement" (without quotations), I couldn't find it's power requirement, but I did find that it runs at 5400rpm and is backwards compatable to USB 1.1 Another problem is cable resistance. Make sure you're using a Qualified USB2 cable with bigger power wires. And as short as possible. I'm using the cable that came with the drive and it is short. A powered hub can solve your problem, but it can introduce other issues with the hub. If the hub has a switch for external power, you get all the volts. I tried a powered hub because I thought I meeded one (later found I didn't need it), but I found out the hard way that starting my system with the hub powered on can blow the motherboard (good thing my laptop was still under warranty) |
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