Heated Bed Stuck at 69c

Hi All,

My temp sensor for my bed fell off and when I went to reconnect it on of the wires touched the wires that actually heat the bed (my fault for not turning the system off obviously). Anyway everything still works (bed heats up, sensor works [verified by testing in extruder's port] etc.) except that now the bed temp is stuck at 69c, however the bed is cool to the touch, and when I turn the bed on the number does not change, but the bed heats up.

Im assuming that the port I was using is now fried, but Im hoping I can avoid buying a new board right now by hooking up the sensor to the slot for the second extruder (which is not in use). I have tried sifting through marlin but cannot find which pins I need to alter, or what to change them to.

For reference my Printer is the GeeeTech Prusa I3X. Ive linked a picture of the board, and if any other info would help id be happy to provide it.

Board

Thanks!

Thermistor heat sensors are quite robust, but it sounds like you've damaged the wire connections, which are VERY thin.

Here's how you test - swap the sensor inputs for the hotend and hotbed. If the hotend is now showing 69C, then the board is fine, and it's just the sensor/wires that are damaged.

Don't forget to swap them back again.

Most likely you will need a new thermistor, but it could just be the sensor wire accidently connected to a metal frame or something like that. (Short circuit, the tiny electrical signal isn't going where it should be going).

Edited 1 time(s). Last edit at 10/25/2016 05:16PM by DragonFire.

Thanks for the reply! I swapped the extruder and the thermistor, and it read the temperature correctly, and even when i had the heated bed port empty it continued to read at 69c. Any ideas?

Hmmm. Does sound like a fried board.

The snag with continuing with it is that, if it's always going to read at 69, that might stop it printing at all...

Probably hackable, but I don't know of any 3D printers that have 2 hotbeds. It's going to cause issues if you try to fool the system...

... on the other hand, it's probably just swapping the pin assignments inside Marlin, so that a different pin is read. Can't help you with which one, I don't know the Geetech board...

Edited 1 time(s). Last edit at 10/25/2016 06:00PM by DragonFire.

It's probably in pins.h somewhere... which pins the geetech uses. Probably commented.

EDIT: No it isn't... you are going to have to check which board is defined in boards.h, then look through pins.h.

When you find the right entry for the board you have selected in boards.h, swap the TEMP_BED_PIN value for the TEMP_1_PIN value, to swap the inputs over.

Save, recompile, should fix it.

I tried the Geetech website, it doesn't seem to be working. If indeed it ever does... never tried it before.

Edited 2 time(s). Last edit at 10/25/2016 06:22PM by DragonFire.

Ya I tried swapping the number that has bed temp commented next to it, but it seems to make no difference, even when i swap it to the extruders pin.

Ah, but you got to do it on the right set of definies - each board has a different set.

Sorry, I'm not helping you much here, but I think you got the right idea - just got to find the right pair to swap over.

I guess you could swap them all over. Kind of a shotgun strategy.

Easy way to do that - 3 find and replaces...

Find TEMP_BED_PIN, Replace with TEMPCHUNKEYLOVER (all of them)

Find TEMP_1_PIN, replace withe TEMP_BED_PIN (all of them)

Find TEMPCHUNKEYLOVER, replace with TEMP_1_PIN (all of them)

That should do it. Save and recompile.

Awesome! Ill try that, and dw your being plenty helpful.

Quote
DragonFire
It's probably in pins.h somewhere... which pins the geetech uses. Probably commented.

EDIT: No it isn't... you are going to have to check which board is defined in boards.h, then look through pins.h.

When you find the right entry for the board you have selected in boards.h, swap the TEMP_BED_PIN value for the TEMP_1_PIN value, to swap the inputs over.

Save, recompile, should fix it.

I tried the Geetech website, it doesn't seem to be working. If indeed it ever does... never tried it before.

Thanks! That fixed the issue! I didnt realize there were different sections for different boards, makes total sense though.

Edited 1 time(s). Last edit at 10/25/2016 07:09PM by chunkeyolover59.