GT2560 A+ MOSFET broken

[MBO]

Hello All,

after upgrading my I3ProB to a I3ProC, I had an issue that blew both fuses.

As I found out when using new fuses, it was the Transistor for the Heatbed burning through.
Why it happened after modification I would really like to know?
But at the moment it seems just a coincidence.

Well I found the issue with my Multimeter, the Heatbed Transistor always has 0 Ohm between Drain an Source, and I cannot switch off the Heatbed by software. (Heatbed itself has 1,4Ohm and is heating normally)

As I do not have a matching Part somewhere around to just solder in a new Transistor, I thought to use an external MOSFET I happen to have here.

Now my Question: Is there any reason not to solder the connection cable for the external MOSFET to the Gate Connection point on the Control Board?
I don't want to ruin the board unnecessarily.

Thanks for your help!
Martin