Welcome @guilleDMUPM, to the community!
Just how trustworthy the dealer's product website is can be seen from its description, in which it refers to the device as an IGBT. You were almost certainly sold counterfeits because these devices have not been produced since the early 90s of the last millennium. Since you can't refer to any data sheets for such counterfeits and can't even estimate the behaviour, I can only advise against using them in such an infernal power machine.
Unfortunately, I am not aware of a direct replacement. At first glance, the IXFN140N20P appears to be a pin-compatible replacement, but it differs significantly in some respects:
- Gate Threshold Voltage: 2.5-5V instead of previously 2-4V
- Rdson max 18mohms instead of the previous 14mohms
Incidentally, the power amp MOSFET in a Class-D amp cannot supply too much current, but at most be driven incorrectly or insufficiently. The gate threshold voltage in particular, which may be at the upper end of the IXFN140N20P, would then lead to inadequate switching of the MOSFET. However, the gate resistor also plays a decisive role and must be adapted to the parameters of the MOSFET for such power classes. However, without detailed schematics of the output stage and data sheets for the ICs, which have presumably also been discontinued, it is difficult to make a recommendation.
Regards
/Peter
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