RAMPS 1.4 not powering mosfets without USB power

Hi, me and my brother are build two 3d printers, everything was going fine till I found that the Arduino Mega voltage regulator were heating a lot, then I found that the RAMPS board was powering the Arduino with 12V. To solve this problem I made a 5V voltage regulator to power Arduino and removed one diode from the RAMPS board as sugested in another topic RAMPS wiki.
Except for the LCD contrast everything was working fine, but now I noticed a problem I haven't noticed before: The MOSFET power outputs (bed, nozzle, fan) can only be turned on when the board is connected to the USB.

The root of this problem is the Arduino voltage regulator heating a lot when powered thought the RAMPS board. And I'm not talking about mild hot, is hot to the point that you cannot touch it.

Any suggestion?

See [reprap.org].

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I had a similar problem, my 5 volt regulator actually died so ended up replacing it with this DC-DC Step Down Buck Converter 1.5V 3V 5V 9V 12V and Adjustable at 3 amps.
I also killed my Ramps 12 volt regulator and at the same time replaced it shown below, link show the process for both.


[reprap.org]


This is my suggestion, there are many on this forum that have had similar problems and many different way to fix the low current from the these regulators.

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Computer Programmer / Electronics Technician

Thanks for you reply guys, but I found the issue.
The issue is that feeding the Arduino with 5V through the DC jack is not enough since the voltage regulator on arduino needs at least 7.2V as input to regulates to 5V... So the solution was changing my external voltage regulator to a 8V one. Now the screen constrast is perfect, the arduino's voltage regulator does not heat and everything else works just fine.