Heated bed keeps disconnecting at ~77 degrees...

Hello!

I've look all over the forum and the internet for the answer to this question, but have been unsuccessful... I am currently building a Prusa Mendel. I was using a 12V computer PSU, but my heated bed wouldn't go any higher then 90degrees celcius because voltage simply wasn't high enough...

I bought a new PSU with adjustable voltage (~13v to 18v, 25amps), when I connect the PSU directly to heated bed, it heats up easily to 110 degrees celcius with 15V, but when I connect the new PSU unit to RAMPS 1.4, the heated bed just disconnects at around 77 degrees celcius and doesn't turn back on unless I reset printer.

I tried to input 12V using my old PSU at bottom two (stepper motors and hotend) and top 2 inputs 15V using the new PSU (heated bed) and same issue...


Would anyone have any advice?


Thank you in advance!

C;

Maybe your heated bed mosfet is overheating. Mine had a similar problem until I put a cooling fan over the board.

IT WORKED!

Thank you brother!