MakerGear Forum

I am getting a used M2 up and running, but it keeps blowing the 15A bed heater fuse.

I am using a 24v linear power supply, all I have available. Is this the correct power supply. I have
read about using two different voltage power supplies and that a single 24v can be used.

Shorted heater bed? Can anybody tell me what the bed resistance should be.
All helpful suggestions greatly appreciated.

tj

It depends on the age of the machine, but yes, the older M2s run 12V into the heater, but generally these came with a version of the RAMBo that had an 18V circuit breaker in the back instead of the fuse (which was eventually replaced because the device has a history of catching on fire, although I've never heard of this happening on a RAMBo). There may have been a short period in which the M2s shipped with both the RAMBo board with the 15A fuse and the 12/18V split power supply.

The easiest way to figure out which bed you have is to measure the resistance across the terminals. The old heated bed (12V) is 1.5 ohms, the new on (24V) is 3 ohms. Note that 24V across 1.5 ohms = 16 Amps, so yes, that would blow a 15A fuse.