MP3 player ghost battery

[PerranOak]

I have an old style MP3 player and am investigating it … well I was!

I wanted to see what current it took so I removed the AA battery and connected the player's terminals to the PSU. However, it would not start.

To cut a long story short, I tried "everything" including putting in a false battery in case, somehow (magic?), it can detect a battery, but nothing worked.

When I put a battery in - in the ordinary way - it works perfectly.

What could be going on?

Cheers.

[shakalnokturn]

Some devices (Sony?) had a switch for battery type detection, primary or rechargeable.
Doubtful, but wire resistance could be a problem with external power, try decoupling close to MP3 player.

A couple of photos would help: Player and test setup.

[NiHaoMike]

Probably too much inductance. Try adding a capacitor right at the battery terminals, 100uF or more.

[PerranOak]

Cheers both.

While investigating, I forgot to set the current limit on the PSU - now I've fried it totally. I must have shorted something or something.

Thanks anyway.