Hi from France.I own more than 20 E-H pedals old and new and I’ve got a question for techs: one of my first pedals the Deluxe Big Muff Pi purchased in the late 70’s has a low freq hum. When I bought it the other one available in the shop had the same hum, so I thought like the seller that it was normal. I always use it as it’s my favorite BM Pi. I made a google search and could see and hear on YouTube the same one with absolutely NO hum ! I also read somewhere that it was a known problem on some early series that could easily be repaired. On an old site Howard Davies wrote years ago he could repair this but didn’t want to accept overseas boxes, and anyway I don’t want to send it anywhere, love it too much ! I remember he wrote “I make a mod that completely eliminates this hum”.
My model is the one with the Blend switch, PCB : EH 3053 C . I cannot find its schematic diagram, nor the mod that should be done to suppress this permanent low frequency hum. Maybe it could only come from the lack of filtering condensers, or a defective series of ac transformers ?? All I know is mine wasn’t the only one to have this little flaw. I hope someone will be able to help me repair it for its fortieth anniversary !
Happy new year to everybody here.