Power supply for built-in battery powered MP3 players

[kuma33]

I've tried to make an external power supply for an old Samsung YP-U3, then for some cheap, noname player, but i failed both cases.
I used a LM317 based circuit, but when i replaced the Samsung's internal battery with it, the player died, it didn't turn on anymore, it produced only some led-blinking (what is normal while turning on), but the screen didn't turn on, even when i placed the battery back, and removed the power supply, so eventually it died..and that happened, when i tried this with the cheap, brandless player. The circuit wasn't bad, because a couple of months ago, i found some old, AAA battery powered player, i hooked them together (i lowered the voltage first to 1,5V of course..), and it worked perfectly..
Is there some difference between the external and internal battery-powered portable players?

 

[Mooly]

It should work if the power supply is correctly designed. You need to ensure that the voltage is correct both at light or no loading as well as at full load current. That can be an issue for many regulators... check the data sheet as some specify a minimum load current. If that is not met the output voltage can rise.

Something has gone astray in your build for it to cause these problems.

 

[kuma33]

I replaced the feedback resistor (usually "R1") from 240 to 120 Ohm, it works fine, i measured also the player's input currents, they were truly low, so maybe this was the cause of my previous player's deaths. Thanks for the suggestions, everything is fine now!

 

[Mooly]

Thanks for the update. Pleased to hear you got it sorted.