I realize what bad form it is to ask for help in one's first post. However, I'm not asking. I'm begging for help. :-) Also, this is truly much more of an electronics question than a computer support question, but I'll first describe what I've done in order to help rule some things out.
I have two identical laptop PC's (Toshiba C655-S5060, but I don't think that matters - and actually I have three of them but to keep this simple I'll just use two). They were bought at the same time, are used the same way with nearly identical applications, and have been used about the same amount. They're almost exactly one year old with original batteries. They are low-cost laptops (possibly a clue) but have been solid overall so far. They belong to my twin teenage sons.
Just before Christmas, one of them began having a problem with his iPod repeatedly connecting and disconnecting, in rapid-fire fashion, so he couldn't get it to sync. Initially I assumed it was just the latest in a series of iPods my family has owned that died for no apparent reason, but began troubleshooting anyway. I plugged the "bad" iPod into the other kid's laptop, and it connected just fine, and stayed that way. Hmm, maybe it's not the iPod after all...
So back on the now-suspect laptop, I did all the usual things - uninstalled/reinstalled iTunes (probably 5 times by now), reinstalled chipset drivers, turned power management off for all the USB hubs/ports, reset the iPod itself (probably 20 times by now), checked BIOS configuration & version - nothing seemed to make any difference. I scanned for viruses/adware using both MS Security Essentials and Malwarebytes with current signatures - nothing found by either one. Still, every USB device I try on this laptop other than the iPod works just fine.
Digging around even more on the 'Net, I found a post from someone who had concluded that these 3rd generation iPod Nanos were particularly sensitive to voltage, and would disconnect much more easily than most devices if the slightest variation in voltage occurred at the USB port. So... I thought, "there's an angle I hadn't considered, maybe his laptop battery is just getting tired."
So I did a bit of side by side testing, with the two laptops set up next to each other, cold booted, each plugged in to their respective AC adapters (which both test fine on output voltage BTW). I made up a USB breakout cable so I could monitor the voltage at the ports. (These laptops have two USB ports, physically adjacent, and both directly on the motherboard. As far as I can tell, whatever voltage is present on one port, is the same on the other port, at least when no load is present.)
On both laptops, the USB voltage is around 5.15VDC when running on the AC adapters, and around 5.10VDC when running without the adapters. When I plug the problematic iPod into the laptop which has no problem, the USB
voltage stays about the same; it might drop a few 100's of a volt but no more than that. And the numbers stay the same whether running on the AC adapter or not.
But - when I plug the iPod into the suspect laptop, the USB voltage immediately starts dropping. After about 30 seconds, the voltage is down in the 4.5 - 4.8VDC range. After several test cycles, it appears the iPod disconnects at about 4.7VDC.
I tried swapping the batteries between the two laptops, cold booted them both, and repeated the test. The voltage drop stays with the suspect laptop, it does not follow the battery.
One of my next theories was that there was a faulty solder connection somewhere on the motherboard, since the delay before the disconnect seemed like it might be a thermal or vibration issue. I pulled the MB out and inspected all the joints under magnification and bright light. I found nothing obvious.
Yesterday I found an Intel white paper ( if you're interested, especially page 5), which has a nice simple explanation of good USB circuit design and a description of some of the more common USB circuit failures they've seen. They make a big point about the capacitor(s) near the USB ports: "A common problem seen here is the use of inexpensive and low quality bypass bulk storage capacitors that have a high ESR or not enough rated capacitance. In accordance to the USB Specification Revision 2.0, the VBUS power lines must be bypassed with no less than 120μF capacitance of low-ESR capacitance per USB port." These Toshibas have a single aluminum electrolytic near the ports, but I didn't note the ratings on it. I wish I'd found this article before I took the MB out (and then put it all back together), since now I'm questioning what is more suspect - a VR, or that cap near the ports. Remember, this is a laptop that Toshiba designed to a price point, and it's a low one.
As a workaround, I did connect a powered USB hub to the problem laptop, and was then able to connect the iPod, do a complete restore and re-sync of a large music library, with no problem. That served the purpose of proving that the voltage issue is the problem, and my son appreciates having his tunes back
. Priorities, you know. 
But an external hub kind of defeats the purpose of a laptop. With it being barely a year old (a couple of weeks out of warranty and Toshiba refused to do anything to help), I'd like to try to fix it. A schematic would sure make me feel better, but that's not likely to happen it seems.
I'm pretty good at soldering and am well equipped to do it. I have the lighting, magnification, etc. But am not sure which direction to go at this point. I wish I would have at least checked the ESR on that cap while I had the MB out.
I'm really sorry for such a long first post, but thought it would be better than having anyone spend time writing a response for something that's already been tried. If anyone has any thoughts or advice, I'd greatly appreciate hearing them!
Mike
Olathe, KS
I have two identical laptop PC's (Toshiba C655-S5060, but I don't think that matters - and actually I have three of them but to keep this simple I'll just use two). They were bought at the same time, are used the same way with nearly identical applications, and have been used about the same amount. They're almost exactly one year old with original batteries. They are low-cost laptops (possibly a clue) but have been solid overall so far. They belong to my twin teenage sons.
Just before Christmas, one of them began having a problem with his iPod repeatedly connecting and disconnecting, in rapid-fire fashion, so he couldn't get it to sync. Initially I assumed it was just the latest in a series of iPods my family has owned that died for no apparent reason, but began troubleshooting anyway. I plugged the "bad" iPod into the other kid's laptop, and it connected just fine, and stayed that way. Hmm, maybe it's not the iPod after all...
So back on the now-suspect laptop, I did all the usual things - uninstalled/reinstalled iTunes (probably 5 times by now), reinstalled chipset drivers, turned power management off for all the USB hubs/ports, reset the iPod itself (probably 20 times by now), checked BIOS configuration & version - nothing seemed to make any difference. I scanned for viruses/adware using both MS Security Essentials and Malwarebytes with current signatures - nothing found by either one. Still, every USB device I try on this laptop other than the iPod works just fine.
Digging around even more on the 'Net, I found a post from someone who had concluded that these 3rd generation iPod Nanos were particularly sensitive to voltage, and would disconnect much more easily than most devices if the slightest variation in voltage occurred at the USB port. So... I thought, "there's an angle I hadn't considered, maybe his laptop battery is just getting tired."
So I did a bit of side by side testing, with the two laptops set up next to each other, cold booted, each plugged in to their respective AC adapters (which both test fine on output voltage BTW). I made up a USB breakout cable so I could monitor the voltage at the ports. (These laptops have two USB ports, physically adjacent, and both directly on the motherboard. As far as I can tell, whatever voltage is present on one port, is the same on the other port, at least when no load is present.)
On both laptops, the USB voltage is around 5.15VDC when running on the AC adapters, and around 5.10VDC when running without the adapters. When I plug the problematic iPod into the laptop which has no problem, the USB
voltage stays about the same; it might drop a few 100's of a volt but no more than that. And the numbers stay the same whether running on the AC adapter or not.
But - when I plug the iPod into the suspect laptop, the USB voltage immediately starts dropping. After about 30 seconds, the voltage is down in the 4.5 - 4.8VDC range. After several test cycles, it appears the iPod disconnects at about 4.7VDC.
I tried swapping the batteries between the two laptops, cold booted them both, and repeated the test. The voltage drop stays with the suspect laptop, it does not follow the battery.
One of my next theories was that there was a faulty solder connection somewhere on the motherboard, since the delay before the disconnect seemed like it might be a thermal or vibration issue. I pulled the MB out and inspected all the joints under magnification and bright light. I found nothing obvious.
Yesterday I found an Intel white paper ( if you're interested, especially page 5), which has a nice simple explanation of good USB circuit design and a description of some of the more common USB circuit failures they've seen. They make a big point about the capacitor(s) near the USB ports: "A common problem seen here is the use of inexpensive and low quality bypass bulk storage capacitors that have a high ESR or not enough rated capacitance. In accordance to the USB Specification Revision 2.0, the VBUS power lines must be bypassed with no less than 120μF capacitance of low-ESR capacitance per USB port." These Toshibas have a single aluminum electrolytic near the ports, but I didn't note the ratings on it. I wish I'd found this article before I took the MB out (and then put it all back together), since now I'm questioning what is more suspect - a VR, or that cap near the ports. Remember, this is a laptop that Toshiba designed to a price point, and it's a low one.
As a workaround, I did connect a powered USB hub to the problem laptop, and was then able to connect the iPod, do a complete restore and re-sync of a large music library, with no problem. That served the purpose of proving that the voltage issue is the problem, and my son appreciates having his tunes back
. Priorities, you know. But an external hub kind of defeats the purpose of a laptop. With it being barely a year old (a couple of weeks out of warranty and Toshiba refused to do anything to help), I'd like to try to fix it. A schematic would sure make me feel better, but that's not likely to happen it seems.I'm pretty good at soldering and am well equipped to do it. I have the lighting, magnification, etc. But am not sure which direction to go at this point. I wish I would have at least checked the ESR on that cap while I had the MB out.
I'm really sorry for such a long first post, but thought it would be better than having anyone spend time writing a response for something that's already been tried. If anyone has any thoughts or advice, I'd greatly appreciate hearing them!
Mike
Olathe, KS
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