Bed heater MOSFET on Duet 2 WiFi failed - replacement?

Triet

The MOSFET "IPD036N04L G" of my Duet 2 WiFi used to heat the bed died and it is not available anymore (old model). Does anyone know an equivalent model to be used as a replacement?

Here is its datasheet:
http://www.icbase.com/File/PDF/IFT/IFT03781303.pdf
and here is its picture (borrowed from another thread):

The terminal block for Vin and GRD (coming from the PSU), precisely the GRD receptable, got very hot during operation and burned a bit. I replaced it but now the bed won't heat. Its diode does not light up when the heater is switched on and I get a heater fault ("heating too slowly") after a few seconds. The bed thermistor is OK. Voltages of both bed output screws of the terminal measured against PSU "-" always shows 24v, same the voltage between gate and source. If looking thoroughly, the sorroundings of the MOSFET appear darkened, as well as its other side of the PCB - I did not notice that at the first glance.

This is a SMD piece and my chances are not good to remove it and solder the replacement MOSFET but I will try. Perhaps I can use an external one instead, but no idea how to control it. Or perhaps I can just solder the replacement on top of the old one (no need to de-solder anything then...).

dc42

@Triet the part number we now use for that mosfet on Duet 2 is TK3R1P04PL,RQ.

If there is 24V on the gate of the mosfet then it has a gate to drain short. It may have damaged the microcontroller pin that drives the mosfet. If it hasn't then it will almost certainly have blown the 180 ohm gate series resistor R20.

If you have a spare heater or fan output then you could use that to drive an external mosfet switch or an Auber Instruments DC-DC SSR.

Triet

@dc42 Thanks! Yes I have a spare pin to control an SSR and will try that connecting PSU "+" directly to one of the bed wires and the other passing through the SSR. I suppose that the bed fuse on the board is no longer functional, so including one in series would be advisable?

dc42

@Triet your PSU may already have a suitable current limit, in which case you may not need the fuse if the wires are thick enough. If in doubt, use an in-line auto fuse holder.

DO NOT use a cheap DC-DC SSR sourced from eBay etc. Use either an Auber Instruments DC-DC SSR or a mosfet switch intended for controlling 3D printer bed heaters.