I tried plugging in the opposite way. Didn’t get hot, but didn’t move either. I plugged in a multimeter and checked the fan pins while the fan was “on”. Zero. Interestingly the extruder fan is still operational. Is it possible I blew a fuse or damaged the MiniRambo with the fan in backwards? The F2 5A fuse is for the extruder heater and fans. Since the primary fan works and the extruder heater, my guess would be the board is damaged. I can snag an ATO fuse just to be sure. I also power cycled the MiniRambo to make sure the firmware had not disabled the fan. Thank you.
The way the fans usually work is that the positive side is always 12V. The negative is either floating or ground. So when it’s on, you should be able to measure 12V. When it’s off, you might measure anything.
I bought some fuses and a tester. The old fuse tested okay. A new fuse made no difference. I thought the Rambo boards were supposed to be more robust. Reversing the wires on a low voltage fan should not fry the board :(. The extruder was heating up before. Now it is not. The thermistors are still reporting around 28.6 C. Is there a chance the board is still good and I can try something else? Are there any diagnostics for the Rambo/MiniRambo. I googled and did not see any… Thank you.
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Fred
They are more robust than the ramps board. The fan is not low voltage, it is low current. When you short it, it will draw high current. Imagine connecting the heated bed to the fan port. Shorting the fan is essentially the same thing.
That said, I think there’s still a good chance something else is wrong.
Can you use a voltmeter to tell if the heating element is still good? Does the heated bed still work?
Is 28.3C reasonable for room temp? That’s about 83F. It’s so cold here, I have forgotten what that feels like :).
You are correct. 28.3C is not reasonable. It should be 20C. That is what my other printer is showing. I seem to have misplaced my multimeter. I will post the heating element voltage. The bed does heat up, and its thermistor does show an increase in temperature, but it starts and around 28.5C as well. It rose to 39C before I turned off the bed. Interestingly, the thermistor for the extruder rose to 29.3C. Heat rising from the bed? Thank you.
There are different types of thermistors and Marlin uses a look up table for each one. If you have the wrong thermistor picked, then it will be wrong, but still change.
They are in Configuration.h. You need to figure out which one is right for your two thermistors. Something like 11 or 8 are the ones I remember using.
It has been a while. The printer successfully completed 5 small jobs, but then the filament got stuck on the roll, pulled the Z-axis arm out of whack, broke the bracket, and clogged the hotend. After much rebuilding, I am about to try and print again, but the temperature is still reading around 29C. I have tried changing the TEMP_SENSOR_0 and TEMP_SENSOR_BED to 8, 11, 1, 60, 13, 61. One had the temperature at 12C, but most are in the 27C-29C range. None are at the expected value of 20C. Interestingly the temperature values for hotend and bed are the same. The bed came from Ryan. I did switch out the thermistor after the above disaster, but like I said, the values are the same for the hotend and bed. Is there another setting that could effect the reported temperature? Thank you.
I have 2 MK8’s here, Tempsensor should be type 1. Since the sensor is not more than a resistor, could you check the voltage on the 5V side? Looks like the voltage is dropping to much.
