Geeetech

Hi there, I need some help. I assembled my new i3X, and at the first test the heat bed heated up to 65°C in short time.

But after 30 Min. while the first testprint, I registered the temp was dropping down to about 55°C.
Now the heat bed is warming up to about 50°C, then it takes very long time for every °C more, can't reach the 65°C after 20 minutes.

I am measuring

• 1 - 1.5 Ohm resistance on MK2A head bed (incl. the LED)
  Heatbed current is about 4-5 Amps when powering
  PSU voltage drops down from 13V to 11V when heatbed powers on
  the power MOSFET on the GT2560 Board is getting warm approx. 60°C (estimated)

Any hints what is going wrong there?

the resistance is in normal range, how's the PSU? you select 220V or 110V?

220V, the first thing I checked before PSU mounting.
Is this normal that voltage is dropping down when heating the bed?

220V, the first thing I checked before mounting PSU.
Is this normal that voltage on PSU is dropping down when bed is heating?

it will drop a little, but not that much like yours, you can use a 12V computer power to test it.

Thank you Mark, I connected a 750W 12V/62A ATX PSU
Started with heat bed temperature of 21°C, target 65°, after 20 minutes I was stuck on 60°C

I have still the original firmware on board. Is the Repetier-Host able to change the PID-values?
Because as said, at the first run it was heating up much faster.

can't remember the Gcode command, you can check the reprap wiki gcode page for the details. If that's not gonna worm, then you might need a new heatbed...

I tried PID autotune for heat bed with
and used S60 for 60 degrees, but also did not reach this in time.
There was also the information that 70°C should be reached in less then 3 minutes.

Next step will be to replace the heat bed, this will take some days.

Thank you for your help to locate the problem.

Hi aps,

on my Prusa I3 M201 the heatbed goes quite quickly to 80°C. Anyhow this model has a 24V power supply and quite a different board. Did you check that all your connectors on the board are ok and not "melted". This could create additional resistance and reduce the effectiveness of the heatbed.

Thank you elocm, but the heatbed was broken in the first 30 Minutes. Replacing the heatbed solved the problem.