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Transforming a speaker from AC to battery Answered


I'm trying to turn an AC powered speaker into some sort of boombox aka run on battery and add bluetooth.

The problem i'm facing is that I'm unsure of where to hack the battery in since the circuit rectifies on-board. My best guess would be to just start probing the terminals until I find a stable power. I also think I have to bypass the 2 transformators (see bottom). But before starting I wanted to see if there is anything I should watch out for, since I don't have too much experience with Li-ion batteries.

Any thoughts, advice, prayers are welcome!


Jack A Lopez

Best Answer 4 weeks ago

It always seems strange to me when someone calls an appliance like this, a "speaker".

In previous usage, a speaker was a passive component. Essentially just a coil of wire and a magnet.

But among the people who write to this forum with questions, "speaker" can mean a plurality of passive speakers, plus the amplifier that drives them, plus the power supply for the amplifier, plus a microcontroller and a display, plus wireless communication, like BlueTooth(tm) or whatever.

Yet the singular noun, "speaker", somehow refers to all this. Maybe it is singular, if all that stuff is in the same box?

Anyway, it looks to me like the bottom half of that circuit board, in the picture you attached, is some kind of switching power supply.

The big question is how many output rails does it have?

Is it a split supply, like with rails at +12 V, -12 V, and ground (0 V)?

Is it a single-sided supply, like with rails at +12V and ground (OV )?

There might be some clues in the heiroglyphics printed on the amplifier IC. If you can read a number printed on it, and find the data sheet for the same, it just might tell you what kind of power it wants, and what pins it wants its power supply rails connected to.

Or like you already suggested, try carefully probing around with a voltmeter, to try to discover the supply rails. Often they will be connected to those big electrolytic capacitors.

Also the ground rail is pretty easy to find. Usually it is the biggest node on the board, and almost everything is connected to it.

Regarding prayers, I think it was Billy Corgan who said, "Save your prayers for when you're really gonna need 'em..."


FancytrollJack A Lopez

Answer 4 weeks ago

Funny that you're mentioning the speaker argument because I was really unsure about how I was going to say it. In my language we say "speaker" in both cases so I just kept it at that.
Anyway, thank you for your time and advice!

Jack A LopezFancytroll

Reply 4 weeks ago

I think I would call it an "amplified speaker", or "powered speaker", or something like that.

I am kind of hoping language like that will catch on, like picked up and used by others, but it might not.

Also I wish you luck with your efforts to figure out this gizmo, and discover its secrets.