Display Power Issue

Hello
My display goes dark while under power soley from the printer PS (12.4vdc across input terminals).
PS and USB powers the display very dimly, but gives printer full functionality.
Only on USB, display brightens to "normal". Any ideas?
Thanks
RAMPS 1.4 MEGA2560 A4988 LCD12864

Edited 1 time(s). Last edit at 10/06/2016 09:12PM by instmkr.

The 5V regulator on the Arduino is overheating. See #1 at [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].

could be too much contrast , try adjusting the preset on the display pcb

Quote
dc42
The 5V regulator on the Arduino is overheating. See #1 at [reprap.org].

Good linkage. Earlier while troubleshooting homing issues I reversed the ramps X axis endstop connector and when triggered the display trouble began.
However cranking contrast full on I could just read and use the display without USB power.
Something changed and now at 12v PS power-up the display does not even try to light up or blink.
Any additional insight also appreciated.

Quote
instmkr

Quote
dc42
The 5V regulator on the Arduino is overheating. See #1 at [reprap.org].

Good linkage. Earlier while troubleshooting homing issues I reversed the ramps X axis endstop connector and when triggered the display trouble began.
However cranking contrast full on I could just read and use the display without USB power.
Something changed and now at 12v PS power-up the display does not even try to light up or blink.
Any additional insight also appreciated.

What you're describing seems to be fairly typical failure for the 5V regs on these boards. For some reason they often don't fail completely, but become marginal and unreliable. Bottom line remains the same - you will need to replace the 5V reg either individually or with the entire board, or always supply 5V directly.

Edited 1 time(s). Last edit at 10/07/2016 08:48PM by JamesK.

The 5V regulator on mega 2560 must have been the trouble as a new 2560 fixed it.
Many thanks for your input.

Now if can just solve "heating failed" on extruder re-heat.
And a print that x/y sits still while the extruder makes spaghetti...