K3507 Inverter 250 Watt - Cross Polarity

I have a K3507 Power inverter which has been connected to the 12V input cross polarity. Is it possible to repair and if so how ? Thanks

The unit features protection against polarity inversion by means of a fuse and diode D17.
If replacing both does not solve the problem, then you can return the unit for inspection/repair.
Although this item has been discontinued 11 years ago, we can still service it
Please return your kit to:

Velleman Projects Tech. Dept.
Legen Heirweg 33
9890 Gavere
Belgium