[Ralph]

I have measured every component before I soldered it in the PCB and the SK170 fet was not recognized as a fet but as two diodes. I use Peak CDA75 component tester for transistors.
Should i require a new one even though they seems very rare or get a replacement if thats possible.

[JPK]

I would go ahead and solder it in place. These components are very reliable. It is probably the tester which gets confused.