Thanks to all responding. K3 # 8876 works fine when KPA3 from my older K3 #2876 is plugged in. The KPA3A from K3 #8876 will not work when plugged into K3 #2876. So this rules out the riser board K3IOA and the K3 itself. KPA3A #8876 is kaput (ha, that is a german word!) . Did some checks, visual inspection etc. but nothing found so far. -- 73, Martin