Apparent short between +ve ext supply pin and ground - surely this not right?

Hi All

I have been trying to find out why my Arduino Uno won't power up when I have an appropriate external power supply plugged into the 2.1 mm ext supply connector on my board.

I have checked the power supplies, I have three, and they each output 12V with +ve center pin.

So, I did some quick checks on the Arduino board, and I am wondering if an expert can correct me if I am mistaken, and advise please.

I checked with a continuity meter between the center pin of the external power connector, and the three soldered points on the bottom of the board directly underneath the connector - as per photo!

On each of the points I get a short!!! Surely that isn't right... is it?

Can anyone advise please? thanks...

What happens if you just put an unused power adaptor plug in there does it still read short ?

Like many of the 3.5 and 1/4 inch jack plugs allow a short when disconnected to keep the signal flowing through that jack.

Ballscrewbob:
What happens if you just put an unused power adaptor plug in there does it still read short ?

Like many of the 3.5 and 1/4 inch jack plugs allow a short when disconnected to keep the signal flowing through that jack.

Hey Bob - I wasn't aware of that - thanks for the info!

When you say unused, do you simply mean plug the PSU connector in but don't power it up?

So, I connected a PSU, but didn't power it up - but obviously can't get ot the center pin directly now as it is connected to the PUS. SO Checking the continuity between the three solder points on the underside of the Arduino Uno, there is stilla short between eahc of them - regardless of which ones I test!

So, I am guessing there's a faulty connector, or that the circuit board is faulty in that area. The Arduino works fine, apart form this!

Just metered mine up and yup its normal.

Some power sockets do allow a return path but usually have an extra pin for that.

Unos dont.
One nearest long edge of board and front short edge both return continuity.
Only the rear pin is used for positive side

Thanks Bob! Very strange though... I wonder why none of my three PSU's are causing the Arduino to power up then?

I very nearly went and ordered a new Uno too!!

Not sure what to do to fault find this now? Any suggestions?

It's not a huge deal not being able to power up the Arduino from external PSU, but I should be able to nonetheless. Thanks for your input, Bob!

If its 12 volt or higher then there have been lost of posts about the regulators popping on REAL boards but non on clones.

I always run below 10 volts here for the power jack. and both my clones and real boards are still quite happy to do what I tell them even if I tell them wrong LOL

I have a UK sourced Arduino Uno clone, and each of my supplies are regulated 12volters, yes.

I'll leave it for now, and just use them connected to power external kit I need such as motors or heaters etc.

Thanks again, Bob!