Maybe I should replace the network filter. HYTEK 8444 RC1150002 is unknown for Google. I have seen in an earlier thread that the SE/30 has a filter as described in

viewtopic.php?f=7&t=18026&hilit=bourns&start=25



I have measured the resistance between pin 2-19, 3-18 etc in my 512k and its 50 ohms so maybe it’s the same as in the SE/30? I can´t measure the capacitance.

Anybody know if I can use the same (for example Bourns 4120R-601-250/201) in the 512k?

Its available on ebay.