I've just pulled my duemilanove board out of storage, and it works fine through USB. However, when I plug it in via the barrel jack, the PWR light just flickers dimly, and refuses to work. I've tried with several different wall-plugs, and now I'm stumped. Could anyone help me out?
Check the power at the Vin pin and at the +5V pin. The Vin pin should be between about 7 and 12v. +5V should be a solid 5V. If Vin is low there is something wrong before the regulator. If Vin is good and 5V is low there is something wrong with the regulator or something after it.
The barrel jack is outputting 9v
The Vin pin (measured to ground) is 9v
The 5v pin (measured to ground) is 1.4v
Does this mean I need a new regulator? or is there something else which could have died?
timmydavie:
Does this mean I need a new regulator? or is there something else which could have died?
From the schematic it looks like the 5V regulator is the most likely failure point. It's the only active component between Vin and +5 and it isn't used for USB power:
It should not be as hard to replace as most surface-mount components.
Thank you. Just one more question: Could any 5v voltage regulator work?
I.E one like this:
http://www.maplin.co.uk/1a-low-dropout-fixed-positive-voltage-regulator-46321
It would probably work if you could get it to fit and the pins are in the same order as the one already there.
Another choice would be to use an external regulated 5V supply and connect it directly to the 5V pin. Most modern cellphone chargers have a mini- or micro-USB connector and would supply regulated 5V.