RAMPS 1.4 smoked extruder heat.

While doing a test print my wires for my heat resistor arc'd and now my j head extruder will not heat. Will I have to replace the whole ramps board or can I replace just a part?

Thermistor shows temperature but when I set the temp in pronterface there is no voltage on D10 and the LED does not light up indicating that it is trying.

Heatbed works fine and does what it is supposed to.

Any other troubleshooting I can do to narrow down what smoked?

Thanks in advance for your help.

Check the underside of the RAMPS board (removed from the Arduino Mega) for any burnt tracks. This is a good indicator.

Next, there is a PTC fuse (F1) that covers all the motor electronics, and the D9 and D10 outputs (usually Fan and Extruder). If your motors work, then the fuse is fine, otherwise I'd suspect the fuse has blown (they're NOT supposed to be able to blow, but I've seen it happen).

Next, check the FET that runs D10 (labelled Q1). You need to see if when the extruder is switched on, there is a voltage at the gate of the FET. You can do this by measuring the voltage at R13 (it's a 10 Ohm resistor, right near LED1). It's small but you should be able to get a voltmeter probe to it. Compare against ground (eg: -V or COM probe to the -V input to RAMPS from your PSU).

- If there is ~+5V on both sides, then it's the FET (failed gate open circuit).
- If there is ~+5V on one side and zero on the other, you may have blown the resistor (though this is unlikely) but it's more likely the FET (failed gate closed circuit).
- If there is ~+5V on one side and something non-zero on the other, then the FET may still be dead (failed gate with some resistance).
- If there is no ~+5V on either side, then you may have an issue with the Arduino Mega.

To test the Arduino Mega, you'll have to take the RAMPS board off and run a test sketch that sends the pin for D10 high. (Digital pin #10).

If you're not using a Fan, you can always change the firmware to swap D10 and D9 around in the firmware (changing pins.h in Marlin for example). You can then hook up your extruder to D9 and it should just work.

Note: The LED's for Extruder/Fan/Heated Bed all run from the output of the FET. If they don't work, the output is unlikely to work (unless the LED has died). This means you don't need the outputs connected to test everything, which is useful when you're trying to figure out an issue.

PS: Never disconnect/reconnect cables or boards while the power is on - always turn the power off first. This is specifically relevant to motor connections and driver boards, but it makes sense to do it with pretty much every cable into a RAMPS board, just to get into the mind-set of always doing it.

Thank you! I will get started on going through each of these. I hope it is something that I can fix. I only use the fan on the ramps board because my heat bed would not come up to temp unless I cooled the fuses. I can use a usb fan to do that. What part of the pins.h do I need to change to use D9 for the extruder heat? (Marlin Firmware)

Can you all please tell me the best way to wire the heat core. I have tried solder but because of temperature the solder melts. Crimping was difficult because there is a fine line between getting it crimped and cutting the wires internally. This last attempt was alligator clamps. These worked great until somehow there was a short through the kapton tape that I used as an insulator. I really don't want this to happen again.

Thanks for the awesome information.