I still havent resolved mine yet either. I have been speaking to Ian at RepRapPro and it looks like the restance of my heatbed is too low. It should be 1.3 ohms and mine is 1ohms. The lower the resistance the higher the current.
In my case my heatbed heats up supper quick but this quick heat up means that its drawing too much juice (11.3amps in my case) this is causing we Melzi to disconnect from the computer as the combined load 11.3 for the heatbed and ~3.5 for each of the hot ends equates to more than 20amps.
EDIT: Here is an alternative 30amp power supply that might do the trick: [www.amazon.co.uk]
In my case my heatbed heats up supper quick but this quick heat up means that its drawing too much juice (11.3amps in my case) this is causing we Melzi to disconnect from the computer as the combined load 11.3 for the heatbed and ~3.5 for each of the hot ends equates to more than 20amps.
EDIT: Here is an alternative 30amp power supply that might do the trick: [www.amazon.co.uk]