neve 1073 presence hum

Hi I've build 1073 with original layout ( pcb from AVDO)
Strange problem:
only when the presence switch is on I've a big Hum ( 10bd+ from bypass)
Carnhill inductors
ba211 9050 -9044
I've checked all the connections different time and all seems correct....
All is working the problem is only the hum with presence on.

Also checked the 284 board and all seems fine...
Suggestions?

Problem solved!
Main transformer out of the case....
Thanks!

ilfungo said:

Problem solved!
Main transformer out of the case....
Thanks!

Click to expand...

You got to indeed be carefull they can pickup some hum. Using toroidal power transformer with shielding and also shielding of the switch wires it is possible to put the transformer in the same case.
However it's not easy.
Most of the time I shield some of the wire going to the switches. It's a line signal so not extremely sensitive but it can help to reduce hum.
As far as I know they didn't do this in the original 1073 but they also didn't had the power transformer inside.

Best regards