HI Johannes, Thanks for your response. I have replaced all the electrolytic capacitors on the power supply including the two large 4700uf and 2200uf ones. Voltages are adjusted and spot on. Since my original post I have noticed that if I disconnect the harness from CN05 from the clone KLM367 (i.e. the connector comes from the patch select, write enable/disable and tape enable/disable part of the KLM371 Programmer Board), patch A.1 comes up without the problematic modulation when I turn the synth on.