Short circuited. Arduino or RAMPS?

Hi,

Today I was being careless and forgot that I was using a metal plate on top of the heated bed with exposed soldering joints and tried to change the plate while the heated bed was on. As a result, the metal plate created a short circuit, accompainied by some smoke and fire effects on RAMPS side. Now, when I turn on the printer, the heated bed is always on, even though I didn't set anything. I have changed the entire electronic setup but was wondering if the problem is at RAMPS or at Arduino, so that I can save the healthy one and throw away the faulty one. How can I locate the origin of the problem?

Thanks

It's plausible that you burned the FET on the RAMPS causing it to always stay on. Double-check with a multimeter that the bed FET is not conducting (drain to source) when no voltage is applied to it. Make sure you do this when the printer is off. If it is, you need to either replace it or replace the RAMPS.

It is also, unfortunately, possible that the Arduino is damaged and the pin that controls the bed is stuck high (or low).

My recommendation: find the pin on the Arduino that controls the heated bed, see if it changes when it should (i.e. when you turn the bed on or off). Ideally, do this with the RAMPS unplugged from the Arduino.