Olaf, Your best answer will come from Elecraft support. 73, Don W3FPR On 2/3/2020 4:10 PM, dl7jom at darc.de wrote: > > We have a KPA500 in our station setup of HU1DL. > > After some days of operation (and changing of bands, filters, antennas), > the T/R pin diodes are blown (D8/ D9). >