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Very loud mains hum from audio out

Started by simeonnotsimon, January 10, 2018, 01:27:20 PM

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Hi. Ive just taken delivery of a B stock Atmegatron. The audio out from headphones is fine, but mains hum from the audio out is very loud and drowns out the audio. I've tried it on several different mixers and different power sockets but the result is the same. Any suggestions much appreciated. !

Ive just found out that plugging into the heaphones socket, which is plugged into the mixer gets rid of the hum, whereas plugging in headphones only reduces the hum slightly.


Hi - I think this is just the internal audio cable that has come loose in the post.  It's very easy to reseat. Do the following:
1)  Undo the 4 screws to the base plate
2)  Reseat the blue cable connected from the 1/4" jack to the PCB
3)  Test it.  If working, do it back up.  If not working, try waggling blue cable while it's on and making sound and let me know if it makes any difference to the issue.

If this doesn't make any difference, email me on


Hi Paul, thanks for getting back to me. I've followed your instructions and the hum goes away when I waggle the blue cable connection to the PCB buy pushing it to the left (see attachment), but returns when I release it. Maybe its the soldering connection of the small white female socket ?


Hmm hope it isn't the soldering on that socket.  I'll probably have to ship it back to me to fix it if it is, as soldering that joint isn't an easy job.

Couple of things to try before getting to that point:
1)  Pull the cable off of the header.
2)  Scratch a screwdriver on the header pins to make sure there's a good metallic contact and there isn't any dirt or gunk on them.
3)  If you have a small flathead screwdriver, push it into the little long thin gaps on the white header socket. This releases the metal clips so the white plastic part of the socket comes off.  Look at the 2 pins, are they bent flat? If yes, try and reshape it so it looks like this: 
4)  Then reassemble and reattach cable.
Another option could be for me to post another blue cable to you. It's fairly easy to replace, you just need pliers to remove the 1/4" jack.

Don't worry if any of this is too much effort or goes wrong, email me and I'll arrange a return. Just trying to avoid you having to be parted from the synth!


Hi Paul

Followed steps 1 thru 4 - the pins inside the housing were a bit squashed so I did what you suggested as well as cleaning everything and adding a bit of deoxit. It all works fine now. Thanks for your help. :)