C3 humming when pressing keys even with tonewheel generator turned off

[LeslieFan]

Hello guys. I'm working on getting my C3 into shape and encountered this strange issue - it emits hum when I press any key, even if I turn the tonewheel generator off. My Leslie is located on the right side, so it shouldn't be the cause. Would anyone knowledgeable kindly point me towards the possible causes of this behavior? Any hints would be much appreciated. I'm still a bit of noob, so please forgive me if the question is too broad

[geoelectro]

I have encountered a few organs that have this issue. If you eliminate the speaker and anything else electronic located on or near the organ then it may be harder to solve. It can be AC wiring in the wall or a transformer located outside on a telephone pole. I have one in Galveston that the hum is pretty severe. They have three transformers just outside near that part of the church. If I turn the organ 90 degrees, it mostly goes away. Otherwise nothing I have tried makes it go away. They used to have a different Hammond there before Hurricane IKE and it hummed as well. In another church they had pretty severe hum, also in Galveston, and moving the organ to the other side of the stage made it go away. Nothing we tried helped in it's original location. These organs came from my shop where they were quiet as expected.
Try moving the organ and see if it helps.

Geo

[enor]

Is your organ a US model, running off a 230/120 transformer? If so, transformer placement in the organ is a rather sensitive matter. If you get it wrong, it will act exactly the way you describe.

[David Anderson]

The reason Hammond Organs are able to have so much signal wiring run without being shielded is that it's a low-impedance system (before the matching transformer), but that also means that the grounds have to be very good, as in low-resistance. A number of grounds in the generator and harness wiring are made with screws, like the screws that hold the filter tray to the generator. Any place where you can reduce ground circuit resistance, you may decrease hum.

But as Geo says, sometimes things are just in the wrong place. I used to live in an apartment where the best place for my Clavinet was against one of my bedroom walls, but our television was on the other side of that wall. If someone turned the TV on while I had the Clavinet on, it would pick up lots of noise from the television circuits.

[LeslieFan]

Thanks to all of you, guys, much appreciated, I'll try moving it around then first.

[gtojimmy]

Has the preamp had the capacitors replaced? I've just done it to my AO28 preamp due to the same issue, and I went ahead and replaced the electrolytic caps, and several other caps and a few resistors. That cured the hum, and the undistorted volume is outstanding now!

[LeslieFan]

yes, I did the recap before this issue had appeared. Anyways, thanks for chiming in, my particular issue seems to have been solved by moving the C3, as suggested above.

[LeslieFan]

Just an update for anyone with the same issue - yes, after some moving around the issue with persistent hum had disappeared. I am now getting some ghost tones on some keys, though, but I'll create another topic for that. Thanks again for the help, guys, you rock!