Turning ac into dc for my speakers

Basically I really need help here. I just bought a set of old small speakers and I wanted to turn the Ac input into a Dc input and I have no idea how to any ideas ?? The step down transformer is inside one of the speakers and I'm not sure how to make it into Dc
Money's not really an option but I don't really want to buy more speakers 

most appreciated Ed :D   

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Do you want to rectify the AC input or do you want to replace it with batteries?

For the later you can replace the plug for the power supply with one that has a switch build in, when the cable is unplugged from the speaker the switch closes, plug it in and it opens - effectively interrupting a battery supply.

For the batteries you need to measure the voltage from the original supply, sometimes it is also stated on the power supply or speaker itself.

For 5V you can use 3 AA batteries, 4 should work too as these cheap circuits are not too critical.

Connect the negative from the batteries to the negative from the original supply.

Positive from the batteries goes to the switch and from there to the positive of the original supply.

3dwardify (author)  Downunder35m2 years ago
I wish to make the speakers portable so I want to replace the ac power with batteries. But the problem is I couldn't find where ok the circuit the ac that goes straight into the board is turned into dc power. On the transformer that's inside the speakers it dosnt specify a voltage output it only specifies that the output is 1.2 amps. I know this sounds like a stupid answer but from the output of the transformer there is 3 wires that come out 1 black called gnd and two blue ac1 and ac2. do you think I would just be able remove both blue ac wires and just replace with the dc power source straight to the board. Obviously checking the output of the ac wires first

theres probly a rectifier, or at least a diode on the board. this converts ac to dc. if it is a full rectifier, it would be fine to feed it dc in place of ac. if it is just a single diode, you'll need to get polarity right, but thats just a matter of guessing and seeing if anything happens.

One potential complexity: your board may require 2 different dc voltages. I suggest checking v from each of the blu wires to blk, as well as v from 1 blu to the other.

3dwardify (author)  Toga_Dan2 years ago

well inside there are 4 diodes In all together and both ac wires go straight to the diodes. Does this mean I can put a dc voltage through without having to worry about the polarity ?

yup. pretty much. a rectifier is 4 diodes in the right arrangement.

3dwardify (author)  Toga_Dan2 years ago

basically I measured it and from blue to blue I just got 0L coudnt work that out xD but from one blue to black it's 12v and other blue to black is about 5v what next ??

Kiteman2 years ago

To turn AC into DC, you need a rectifier.

(Google is your friend.)

3dwardify (author)  Kiteman2 years ago
Oh ok brillaint thank you :D will this make the speakers portable then??

If there is no voltage (apart from mians) staed on the system you have to measure the voltage first using a volt meter.

And if it runs on 12V being portable is being heavy ;)

I have seen small desktop speakers (with a battery compartment) for under 10 bucks, I hope your speakers are worth all the efford.

Sorry, I misunderstood your needs.

See Downunder's comments - you're going to have to pull out the transformer and replace it with batteries.

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