Unplug all modules from the power bus. Reconnect the modules one by one. This might help identify if a specific module is causing the noise. If you find the source, consider using a "Noise Killer Plug" on the problematic module: https://www.midi-hardware.com/?section=prod_info&product=NKP
-- modular01
Oh my goodness. I've never heard of these but oh wow they seem useful. Thanks for teaching me something new today!