Are all barrells on Power supplies interchangable

1

I have this power supply.

It’s amps and volts are ideal, but the barrel is too big and the polarity is incorrect.

If I found a barrel that is the right size, is it SAFE to chop off the barrels from the power supply and solder on my own (making sure my polarity is accurate).
I’m talking about safe for me and my equipment.
Any considerations I need to make?

Pix :heavy_heart_exclamation:

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2

Hi Pix,

Best practice might be to discharge any internal capacitors with a resistor before making any modifications.

I’ve swapped out a bunch of DC barrel jacks for Pheonix plug-style screw terminals with great success for my LED projects.

(I’m unsure if any certifications hold after modifying it, I cant imagine they do)

Liam

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Thanks Liam :slight_smile:

I think I understand the idea here:

  1. some cap gets charged while a circuit is operating
  2. power and ground suddenly disconnected.
  3. electrons in the capacitor can no longer “reach ground” and so stay put.
  4. I want to discharge it safety so it doesn’t discharge through me.

Can you tell me a little more about safe procedures to discharge a capacitor with a resistor please? :pray: :smile:

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4

Hi Pix,

For a 12v supply this could be as simple as putting a 10k ohm resistor across it for a second or two. Then testing with a multimeter.

For higher voltage and capacity capacitors (shouldn’t be present in small smps like this) there’s a much more in depth procedure.

5

As in…

  1. Cut the plug off and expose the two wires
  2. take the positive wire and attach it to 1 end of a 10k resistor
  3. take the negative wire and attach it to the other end of the same 10k resistor
  4. wait 5 seconds

Is that correct?
If I was going to get a shock wouldn’t I have already while I was stripping the wires?
Is this a case of be careful and keep your feet off the floor while working?

As in check for 0 volts across the exposed wires of the power supply?

6

Most of these supplies have a load resistor that drains any charge within a few seconds of disconnecting the device.

For a low voltage supply it is usually adequate to just put the tip of an insulated screwdriver across the ends of the plug. The difference between 10 Ohms and a dead short is not material. If you do cut the and trim the wires then all that is required is to handle each wire separately - the circuit that matters is between the two wires, not between any one wire and earth. But don’t stand on a wet floor in bare feet, just in case.

If it might be a capacitive dropper circuit (unlikely for a 1A supply) then also put a screwdriver across the terminals of the mains plug.

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