MP3 player fried by USB car charger... Common problem????


Just fried my MP3 player, by sticking its mini USB cable in a compound outlet: 3 cigarette lighters, and one USB outlet. The car outlets measure 12.3 V, the USB outlet measures 4.7 V. It is specified for 2000 mA.

I put a switch between the battery and this outlet. The (scooter) battery is wired in series with a similar one, for powering a 2 X 15 W amp; each battery can be switched to a separate compound outlet (described above) for powering gadgets, or to be charged. The plugs of the compound outlets (containing a fuse) have been removed.

The player was playing, connected to the amp; the USB was plugged into the compound socket when the switch was activated.  A very loud pop sounded. Now the sound of my MP3 player is very weak and extremely degraded.... :(

I used to charge it via my computer or by means of the mains USB charger provided with it.  Never any problems!!!

My 1st theory is: destruction by peak voltage... But should the electronics not have prevented this (I did not open it, but it is probably based on a 7805 circuit)???

2nd theory: Current too high. USB is normally 500 mA??? This would mean the USB player behaved like a LED (very low resistance, needs current control????)

I bought my nice former 8 GB player for E 15... But it is now discontinued... Before I connect another one, I would want to know how to keep it alive while playing it hard!




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Re-design7 years ago
Are you sure it's the mp3 player?  It might be the amp.

Is the switch between the battery and the regulator or between the regulator and the mp3player? 

An mp3 player should not be damaged by charging from a usb port.  A computer port can put out 1 amp continuous and more for a short period if shorted.
BobS (author)  Re-design7 years ago
I tested the MP3 player afterward with head phones, and just like the amped speaker sound, it now sounds distorted and feeble. I measured the USB car outlet after the incident (4.6 V). The only thing I can think of is a voltage spike while turning it on (but I don't have a scope). The regulator is integrated in the outlet, so the switch is between the battery and the regulator.

It is not in a car, but part of a bike sound system I am finishing (including an instructable).

The player has an internal battery; I wanted too keep it charged while playing.
BobS (author)  BobS7 years ago
One more question: Assuming the MP3 player was ruined by a voltage/ current spike, what would be a way to prevent this in the future? Perhaps a capacitor or inductor (what kind of value, wired paralel or series???
Re-design BobS7 years ago
My guess is that since the switch is in the power line you got a spike when the regulator first turned on. Maybe it was slow to regulate and your mp3 player took more voltage than it was supposed to get.
BobS (author)  Re-design7 years ago
That is what I think now. Even more setback in this project: It seems the spike has destroyed the tweeter parts of the speakers :(
A computer port can put out 1 amp continuous and more for a short period if shorted.

Officially, only if the attached device asks for it, and the port is prepared to give it.

Steve
lemonie7 years ago

I may be reading this wrong, but I'm getting that you plugged it into a 4.7V outlet and something went "pop"? can you test the USB outlet?

L
Try it on another adapter. If you're lucky, the thing's failed safe and your player isn't GETTING 5 V, which is why it doesn't sound OK.

Were you doing anything like switching off loads in the car ? That CAN generate big transients, called load dumps, in the car electrics, which might, just might blow the 7805.