Faulty or bad quality mk3 heatbed

Hi,

I ordered MK3 heatbed from ebay. I connected it and wondered why it doesn't heat up enough. Only about 45 celcius. I measured the current when heating the bed and noticed it takes only 3A current. That means only 36W with 12V. After that i measured the resistance of the bed and it is 3.6ohm. I removed the wires and measured both heating elements and other was 4.6ohm and the other was 14.6ohm! That seems that my bed is faulty or very bad quality. Has anyone else experienced something like this?

Edited 1 time(s). Last edit at 12/16/2015 03:05AM by juu-zo.

Seems like you got a 24v bed. Bed resistance for a 12v bed should be around 1.5 or so.

Bed should be both 12V and 24V compatible but seems that it doesn't work very well with 12V. Maybe i should order better one.

Did you hook both of the terminals up when you was attaching the wire to the bed? The ground wire should cross both 2 and 3 on the heatbed.

Yes, i connected terminals 2 and 3 with the same wire. Even though the heatbed that I have has different kind of terminals that reprap wiki shows for mk3 heatbed.
Ebay heatbed


Reprap MK3 heatbed

My heat bed is like the one from ebay. The ground wire connects the 2 terminals on the left and the positive just does the one on the right.

Do you see deep scratches under the black paint where the traces might got cut?
That would explain the difference in Ohms between the two traces.
-Olaf

I had one of those ebay aluminium beds, at 12v it took 30 minutes to get to 52deg! 24v was about the same time.
I never ever got it above 58 degrees.

I've now got a silicone bed running from 24v, which hits 110 degrees in about 5 mins - much happier.