problems with ramps 1.4, marlin and pronterface, need help

hi, i´m trying to make an e-waste 3D printer with old cd rom drivers, for that i´m using ramps 1.4 which at the moment have just an atx powersource, 4 pololu a4988 (x,y,z,e0), thermistor(T1) and hot end, PS_ON and the 5v line beside connected. I load marlin 1.1.0-RC8 into the arduino mega (atmega2560). The problem is the next: now i have just connected the 12v line from the atx powersource to the 11a connection in the ramps, if i connect other 12v line to the 5a connection pronterface stop reciving information from the ramps (temperature, endstop status, etc), also i can´t send g codes to the ramps so i can´t turn off the powersource, same problem if i connect the hotend fan in D9.
marlin is configured for atx powersource, PS_ON is connected and i can turn on/off from pronterface, have load marlin several times and pronterface recognise it, i don´t know what else to do
sorry for the bad english, i´m Chilean

"and the 5v line beside connected"

This is just used to power the servo pins. Its not needed

It sounds like yet another damaged voltage regulator on the mega

Remove the ramps from the mega, plug in a 7-12v dv power supply into the dc jack on the mega. (nothing else plugged in, especially not the usb cable)
Measure any 5v lines with a multimeter, ie check the voltage regulator is producing 5v.

pluged in 12v from atx, 5v output is 4.98-4.97v and 3.3v output is 3.32v, is it acceptable?
(ATX output is 12.16v)

Edited 1 time(s). Last edit at 03/05/2017 06:57PM by juampi_ruhe_95.

Thats seem fine.

Next step then

Plug the ramps back on the mega, no stepper drivers drivers, no endstops, no lcd. No other cables at all. bare ramps board.

Plug in the USB cable to the mega, make sure you can still talk to the board.
Then try 12v to the 12v 5amp plug on the ramps and with usb cable also connected. Can you still talk to the mega?
(all this should do is change the 5v supply from using usb +5 to using the 12v in (through on board regulator) )

Edited 2 time(s). Last edit at 03/05/2017 07:21PM by Dust.

I took everything out and it was imposible to talk to the ramps from pronterface, i thik it was because x and y endstops needs to be opened, so i put wires to simulate the endstops but didn't work the only diference now is that the stepper drivers aren't connected.

I would say there is something wrong with your ramps..

You should be able to talk to the mega with bare ramps plugged in especially with no end stops
(the reason for no endstops is people like putting 3 pin end stops in backwards and shorting out the mega power supply)

I put again the drivers and now I can talk to the ramps again, is there a posible solution or just buy a new ramps?

Edited 1 time(s). Last edit at 03/06/2017 09:32AM by juampi_ruhe_95.

I am also looking for a solution to Ponterface not connecting to Ramps 1.4 and Arduino 2560.

... port and baudrate set correct?

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Viktor
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Or perhaps it has a ch340 chip and you haven't installed the ch340 drivers