Thanks sofar all who replied. Some very usefull comments/suggestions
received.

It seems that there was high voltage present / reflected back to the TX
because both the diodes in
the LF-SWR meter as well as the diodes in the TX-output (measuring pwr, and
swr protection circuit.....)
where all gone QRT.............

I now replaced them for 1N4937's , fast diodes, higher voltage.

Aperently the N30 core seems to be not the best solution as an step-up
transformer.
Luckely I do have another 3c85 core (50-60mm) lying around.
Is it better to use this one instead of the N30 material??

I also saw that both the old 2 FET as well as the new 4FET transmitter are
very sensitive for
the load on the output.
The work fine on a dummyload (only 'R')  but when connecting an antenna
things become completly different.
With antenna they show more output on the meter........
This might be a reason why my new TX kept on going into swr protection,
beause of the amount of RF
that was reflected back as a result of the much higher output.

as you can see, still a lot of interesting stuff for discussions.....

73

Dick, PA4VHF