Update: Charging MP3 Player, Coby MP620-4G
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From: JW on 12 Mar 2010 05:23 On Thu, 11 Mar 2010 13:10:55 -0500 "Michael A. Terrell" <mike.terrell(a)earthlink.net> wrote in Message id: <4B99322F.67A4EC2A(a)earthlink.net>: > >JW wrote: >> >> On Wed, 10 Mar 2010 18:27:13 -0500 "Michael A. Terrell" >> <mike.terrell(a)earthlink.net> wrote in Message id: >> <4B982AD1.D3BDE48D(a)earthlink.net>: >> >> > >> >jaugustine(a)verizon.net wrote: >> >> >> >> Hi, >> >> Since my original post, I bought the Coby MP620-4G MP3 player. >> >> The OM says to use a "high power" USB port (computer). There is >> >> no other information in the OM or at their web site on a recommended >> >> charging current if using a different source. >> >> >> >> I can set the maximum current limit on my lab quality regulated >> >> power supply. Note: There is no connection to the USB "data" pins >> >> with this setup. The MP3 player display indicates that it was "charging". >> >> >> >> When I first charged this MP3 player at 200 MA max, which didn't take >> >> very long before the display said the battery is "charged", I loaded it with >> >> several hundred songs (MP3). It played for a little over an hour then the >> >> player "died" (no warning). >> >> >> >> I recharged it at 100 MA max and it played over 5 hours, but I didn't run >> >> it until it "died". Again, when I charged it at 200 MA max, which didn't take >> >> long, it played for 1hr and 10 minutes, then "died". >> >> >> >> For the second time, I charged it at 100 MA max, and it plays a long time. >> > >> > >> > A USB port is supposed to provide 500 mA max. >> >> According to the specification, yes. However, I've seen motherboards that >> connect +5V directly to the USB port. > > > IBM did that with the keyboard on their original XT motherboard, with >no fuse. I had a customer's keyboard cable short at the keyboard. If >he hadn't been at the computer when it happened, it would have set his >house on fire. There was nothing but a few pieces of bare, burnt wire >left. Keyboard cables with 24/26ga wire make nice resistors. :) I'm surprised that IBM would have missed something like that. > Do those motherboards have self resetting fuses? If not, there is no >way I would use them or let anyone else get their hands on them. I'm not sure if they did or not. I'd take a look now, but I can't remember which one of the dozens we have around here was the one wired in that way... All I know is that the resistance between +5 and the USB socket was less than an ohm. Usually there's a switched FET and it will read open.
From: jaugustine on 12 Mar 2010 08:10 Hi, This "problem" with the MP3 player may have been a "fluke". I went into "system tools" and activated a "reset". When I tried to play music, it presented a "refresh" option, which I did. I found technical information on the web about charging an IPOD/MP3 player. This time I set the current limit to 600MA. I charged the MP3 player, and now everything seems fine. John PS, Remove "ine" from my email address
From: Michael A. Terrell on 12 Mar 2010 21:44
JW wrote: > > Michael A. Terrell wrote: > > > > > > IBM did that with the keyboard on their original XT motherboard, with > >no fuse. I had a customer's keyboard cable short at the keyboard. If > >he hadn't been at the computer when it happened, it would have set his > >house on fire. There was nothing but a few pieces of bare, burnt wire > >left. > > Keyboard cables with 24/26ga wire make nice resistors. :) > I'm surprised that IBM would have missed something like that. Even worse, the power supply connector was next to the keyboard connect with a very heavy trace between them. It destroyed the keyboard, but didn't damage the computer. A former IBM EE involved in the first IBM PC design told me that the board layout and production was outsourced, just like the original 63 Watt Astec power supply used before hard drives were supported by DOS 2.xx. He had one of the prototype IBM PC series that had a 128 KB, five slot motherboard with ROM basic and a cassette port. I repaired it for him when the original floppy drive controller died. He was thrilled that I had the same board on hand. I modified his motherboard to the 640 KB version to free up two of the five slots. the old man was thrilled to have it working again, after at least one computer store told him to throw it in their dumpster. > > Do those motherboards have self resetting fuses? If not, there is no > >way I would use them or let anyone else get their hands on them. > > I'm not sure if they did or not. I'd take a look now, but I can't remember > which one of the dozens we have around here was the one wired in that > way... All I know is that the resistance between +5 and the USB socket was > less than an ohm. Usually there's a switched FET and it will read open. A self resetting fuse would fall into that range. -- Lead free solder is Belgium's version of 'Hold my beer and watch this!' |