Heated Bed out of control - trying to disable it

So when I turn on my prusa my heated bed starting turns on and starts heating out of control. I can't turn it off in pronter can change it, can do anything. You can feel that it's getting hotter and the thermistor reads the temperature fine so I can even see what it is in pronter. My reprap buddy says the my mosfet must be burnt out on my ramps.

So I've disconnected and removed my bed. Until I get the mosfet fixed at least. Since I'm printing in PLA want to try printing without heated bed. I can't get pronto to run as it just keeps telling me the hotend temp and the bed at 0 ie
T:185.08 E:0 B:0.0
T:184.98 E:0 B:0.0
T:185.00 E:0 B:0.0
T:185.08 E:0 B:0.0

Anyone know how what to update in marlin, slic3r etc so I can try printing without a heated bed?

The only reason marlin would constantly report the temp like that is if a M190 (Set bed temp and wait) or M109 (Set extruder temp and wait) command was issued. Try disconnecting the USB cable from the arduino and shutting the PSU off. Then reconnect the arduino and turn the PSU back on after 10 seconds or so. If it still does that then try re-flashing the marlin firmware.

Also, it's showing your bed temp at 0.0, is that the temp you're reading when you press "check temp"? If so, then you have a problem with your thermistor wiring.

I've unplugged the thermistor and the heated bed.

When the thermistor is plugged in it reads temp correctly. The issue again is that I can't control the temp on the bed at all - it just keeps going up and up - on off setting it.. nothing works, but the thermistor reads it correctly

I wanted to try printing without a bed but pronter is confused when I unplug the thermistor and bed about what to do. It just keeps cycling temp even though I've set the bed temps to 0 in slic3r and set the thermistor to 0 in marlin

As long as your bed temperature is reading as 0.0 you will never get it to work!

Are you connected to the right pin?
Is the right pin configured in the firmware?
Is the right thermistor table being used?

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

rhmorrison Wrote:
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> As long as your bed temperature is reading as 0.0
> you will never get it to work!
>


Unless he sets the minimum bed temperature in Marlin as 0.