Hello, I'm new to this forum, my name is Juan, they gave me an Elka prelude 22L organ and I can't find repair manuals and electronic diagrams anywhere, I have solved some problems I had, replacing capacitors and so on, but it still has a humming noise. Very annoying when activating the emphasis pedal, I think it may be a lack of ground on a plate or the pedal itself, which I have already disassembled and cleaned, I would appreciate some help, thank you all.

 

It could be the power supply capacitors, causing mains hum.

 

It could be, I will try to replace them to see if it is solved, but above all what makes a lot of noise is when moving the presence or emphasis pedal. The hum is only attenuated a little by leaving the pedal in a specific position, I don't know why that is, thanks for the answer