[Wendymott]

Hi Nick and Refugee. Set up the new FETS as per instructions.. i.e 20 m/A bias per device.. on 80M was getting 50W RF with a two tone generator.. Lovely linear RF output. @ 12.5A DC
Let the PA run for 5 mins..... marginal heating of heatsink. Changed band to 40M. Again reasonable drive waveforms until............switch off..... re applied TX control signal. PA current went to 6A then OFF scale and PSU went into current limit.. devices dead as before.
No sign of "self oscillation".
I am wondering if the 40M LPF has an issue. as it was on 40 previously that the PA died.
Getting expensive 4 FETS dead..dont want to kill anymore.