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quexal 05-11-2008 12:02 AM

How to determine DC amperage required for small device?
I've got a nice salvaged radio that had it's cord cut off. All I know is that it requires 12V DC (it's labeled 12v DC).

What I'm curious about is the best way to determine what amperage is required without frying it.

Can anyone help me with this, otherwise I'm guess I'll start by hooking it up to a 500mA supply and see if it works?

Any help would be greatly appreciated!

jwhite 05-11-2008 05:46 AM

You could hook the device up to a power supply that you know is too big, then use a good meter to measure the amperage it is using. (remember to measure amperage is series)

If the device is in good condition it will not draw more amperage than it needs while hooked up to the proper voltage.

micromind 05-11-2008 11:39 AM

If the radio is very old and uses vacuum tubes, it'll need about 5 or 6 amps. If it's solid-state, it'll likely be less than 1 amp.

As stated above, the best way to determine current is to connect it, and measure current. If the capacity of the source is huge, (like a car battery), make sure there's a fuse of some sort in series with the radio wires.

Remember, polarity is important with DC power. Reverse polarity will destroy semiconductors (transistors and the like).


quexal 05-11-2008 01:04 PM

Hi again,
Thank you both for your excellent and quick replies! I'm much more confident now.

I'll grab a 12v 1A power supply today and test it out!

Thanks again!

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