I am openening a Radio Shack!

c0rbin

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Actually, that's not true. My real post is about those power supplies that come with every little piece of electronic equipment I have owned for the past 10 years.

I need a little help--and since I live in the US, this might be limited to American folks.

You see, the electronic equipment has long since vanished, but I am left with dozens of those power supply chords of the 120, 90 and what-have-you variety.

I am a n00b when it comes to electronics. How can I figure out which of these power supplies are okay to use with electronics I have since acrued?

For example, I have an effects pedal for an electric guitar that has the input for a power supply, but did not come with one.

I have a box full of myriad power supplies.

Batteries being expensive, how do I determine which power supply will be okay to use with the effects pedal so I don't break it?

Is this even a real concern?
 
Yes, it's very important!

Here's all you need to know.

You need to know the VOLTAGE your device needs, whether it's AC or DC (most are dc but not all!), whether the "tip" is positive or negative, and the amperage the device uses.

The device will be marked with a voltage and the "tip" tiagram. So will the power supplies (if not, you must test them with a voltmeter). Just combine the proper transformer to the proper device.

A complicating issue is the barrel size, the size of the connector itself. A similar barrel size is NOT evidence that you can use a particular supply safely.

After all this, the other thing you need to consider is the amperage supplied by the power supply versus what the device needs. It's fine to have a higher rating on the power supply than the device. The reverse is not fine.
 
Thanks, Sundog!

Is there a resource that details these diagrams?

I am a n00b regarding electronics.
 
c0rbin said:
Thanks, Sundog!

Is there a resource that details these diagrams?

I am a n00b regarding electronics.
Click to expand...

The tip diagram is simply a circle with a dot in it. A line will lead from the dot with a + or a - to tell you if the "tip" is positive or negative. Just make sure both diagrams, on the supply and on the device, look the same.
 
c0rbin

Just thought I'd add to sundog's excellent explanation. It is likely that some of the power supplies you have will be "Regulated" power supplies, and some will be "Unregulated".

If you have an unregulated power supplier with a label that says something like "12VDC Unregulated", you have to understand that this supply will only put out 12V when it is connected to some specific predetermined load. Manufacturers often supply unregulated power supplies (because they're cheaper) with pieces equipment that draw a fairly constant current. However, if you hook this supply to a piece of equipment that presents a different load , the supply voltage will be something other than 12V. The only simple way to know what supply voltage you will get with an unknown unregulated power supply is to connect a resistor across it with the same resistance as the input impedance of the device you wish to power and then measure the actual supply voltage under this load, and this will only work with DC power supplies.

If you have a power supply that is labelled as "Regulated", then you can be sure you will get the rated output voltage as long as your equipment doesn't draw more than the rated current (also marked on the PS label) from the supply.
 
c0rbin asked:

Is there a resource that details these diagrams?

A Radio Shack catalog has diagrams and explanations. If you ask for a catalog, and they have any left, they just might give you one. Don't tell them how you are trying to save money or they might make you pay for it.
 
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