No power to Arduino when 12v on, USB disconnected

I have a new Chinese clone RAMPS board (Geeetech) that seems to be working properly when I do basic tests while I'm waiting for my heat bed to arrive. However, if I just turn on the 12v with the USB disconnected then the LCD display stays off - I guess the Arduino isn't powered up. Everything works when I turn on 12v AND have the USB connected.

Now I know about D1, and it is in place - before I disconnect all the wiring (again) and go back in to check that it has been soldered in the right way around (!), is there any other detail I might have missed?

Cheers,
David

check voltage is actuly getting to AM-VIN on the mega.

Vin in this image



There has been talk of a number of boards where the track is broken so the voltage cant get from D1 to the mega.

The other posability is you have killed the voltage regular on the mega.. easy to test. Unplug ramps board, power the mega from the dc jack and try and run something like demo led flash. If it works the regulator is probbaly fine.

Edited 1 time(s). Last edit at 04/04/2015 06:03AM by Dust.

Thanks for that.

I've already done the demo led flash so I'm hopeful that the arduino board is OK (although I do have a spare).

Do you happen to know where the suspect track goes from (i.e. which side of the diode) and to where? If I know where it's supposed to go then I can try tracing it through with my multimeter.

Otherwise I'll just do a search in the RAMPS area.

David

Sorry Dust - I've just re-read your answer and realised that you'd given me that information!

Just to bring this topic to a conclusion - I checked the voltage to where it leaves the RAMPS board and all was OK. Changed the Arduino Mega board and everything worked properly; as the Arduino works from the USB power I suspect that the voltage regulator is not working. I can't find my mains PSU for that board so I can't be sure yet, but it does look like I'll be trying to change that component before too long.

Thanks to Dust for the clues!

Edited 1 time(s). Last edit at 04/09/2015 03:58PM by David J.