Saba Freiburg 6 hum problem

Hello, I am restoring a Saba Freiburg 6 Automatic and am having a problem that I am unfamiliar with. I have restored several Freiburg 6's and this one is strange. I have replaced all the paper and electrolytic capacitors  and the radio plays well. The problem is when you activate the auto tune switch, the radio hums loudly, even with the volume turned down. If you tune off station, the hum lessens in volume, if you switch to MW you still get the hum.If you shut off the autotune, the hum fades out slowly and the radio plays fine. While troubleshooting the radio I discovered that removing the ECH-81 will stop the hum. It sounds like the 60 hZ modulated IF is leaking where it shouldn't be but I'm running out of ideas.  Any thoughts?? Many Thanks, Ross Hochstrasser

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Hi All,

   After many hours of unsuccessful troubleshooting I found a bad solder joint on a bare ground wire running from the center of the ECC83 socket to a junction of a .25 and .1 capacitor adjacent to the  tube socket. Even though the  joint looked solid, it wasn't.  Thanks, Ross

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