Hello. I built a homemade printer using ramps 1.4 and I have a problem with the extruder. When I energize the ramps, the extruder starts to heat up and continues indefinitely (it only stops heating when I remove the power). I believed it could be a problem with the Q1 mosfet but even after replacing it the problem continues. I removed the hotend wires from the D10 connector and measured the voltage with a multimeter on the connector pins. It has 12v as soon as I power the ramps. Does anyone have an idea what it could be? Marlin is configured as 1.4 EFB https://reprap.org/forum/read.php?219,893786,893786#msg-893786 Sat, 15 Aug 2026 18:35:53 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?219,893786,895757#msg-895757 https://reprap.org/forum/read.php?219,893786,895757#msg-895757 Roberts_Clif RAMPS Electronics Sat, 14 Sep 2024 12:34:43 -0400 https://reprap.org/forum/read.php?219,893786,895756#msg-895756 https://reprap.org/forum/read.php?219,893786,895756#msg-895756
I have seen this many time where the hotend heater cartage is not insulated so the heater block is now at 12v all the time, Current doesn't flow due to not having a gnd path. Then the thermistor is screwed to the heater block, if you break the insulation on the leg it forms a gnd connection. Now the hotend is always on.

To test this unplug the thermistor form the controller and turn on the controller. If the hotend now stops heating, that is your issue. (Printer may error and beep at you due to unplugged thermistor)

Note this is actually lucky, if you pinched the other thermistor leg you send 12v into the ADC and kill the pin (or the entire 2560 chip)]]> Dust RAMPS Electronics Sat, 14 Sep 2024 11:24:14 -0400 https://reprap.org/forum/read.php?219,893786,895755#msg-895755 https://reprap.org/forum/read.php?219,893786,895755#msg-895755 With the power turned off and the heat bead disconnected measure the resistance from the positive voltage to the hotbed heater if the resistance is very low or zero then you have a short somewhere.

I have purchased many different circuit boards where a solder blob was the problem, have also had traces that do not make the trip from point a to point b without an open trace.

Example this one was an open trace. Have had others where the two traces are connected together shorting trace to power.
[attachment 121106 Trace.jpg]



Searching the logic of the Marlin Code I found this line of code

#define HEATER_BED_INVERTING true]]> Roberts_Clif RAMPS Electronics Sat, 14 Sep 2024 10:56:10 -0400 https://reprap.org/forum/read.php?219,893786,895754#msg-895754 https://reprap.org/forum/read.php?219,893786,895754#msg-895754
Have you found a solution to your problem?
I am having exactly the same problem, as soon as I turn on my homemade printer using ramps 1.4 the hotend starts to heat up and doesn't stop till the whole printer shuts down with overheat protection error.
Any help would be appreciated.
Cheers]]> nnnooo RAMPS Electronics Sat, 14 Sep 2024 09:50:08 -0400 https://reprap.org/forum/read.php?219,893786,893786#msg-893786 https://reprap.org/forum/read.php?219,893786,893786#msg-893786 When I energize the ramps, the extruder starts to heat up and continues indefinitely (it only stops heating when I remove the power).
I believed it could be a problem with the Q1 mosfet but even after replacing it the problem continues.
I removed the hotend wires from the D10 connector and measured the voltage with a multimeter on the connector pins. It has 12v as soon as I power the ramps.
Does anyone have an idea what it could be?

Marlin is configured as 1.4 EFB]]> magflip RAMPS Electronics Tue, 14 Nov 2023 04:12:59 -0500