Geeetech

Hello, I bought the JIETAI Prusa Mendel i3 with the mk2a heatbed. I program the bed to reach 110ºC to print with ABS but it can not get past the 103 -104 °C. I have checked several times the connections and the welds. Even I solder better one wire that seems wrong weld. But no change.
I have also noticed that the mosfet that controls the hot bed is so hot and when the bed reaches 100 degrees it goes down to 98ºC, and after a moment it goes up again until it is able to pass the 103-104 ° C.

Dear friend,
Thanks so much for your post.
Accroding to the problem you described, pls try to take the following test:
1.Test the resistance value, and the normal value is about 1 Ω to 2 Ω
2. Replace a new thermistor and have a try,checking whether is the thermal resistance loss caused this problem.
Any question pls contect with us freely.

The resistance value is 1.4 Ω. I made a test heating the bed to about 106 degrees. And throughout the test terminals of the bed marked 10.96 -11 volts.

Then I did another test to check the sensor measurements using a lm35 sensor and arduino. I put the sensor LM35 on the crystal and when the thermistor scored 106 ºC the lm35 scored 102 º C. So I think the sensor is fine.
Another thing is that if I leave the bed gets long it's reach 109 ºC but the MOSFET is extremely hot.

How long should take the hot tables reach 110 º C? , Is it normal that the MOSFET is heated to high temperatures?

Dear friend,
Thanks so much for your time.
Accroding to your test, it shows everything is normal, during work the bed cann't reach 110ºC.
And during work the MOSFET is heated to high temperatures that's normal also, if you worry about it, you can put some heat sinks on the mosfet, or you can use a fan.
Any question pls feel free contact with us.
Best wishes