01-06-2023, 03:32 PM
Hi Marco,
Welcome to the Phorum. But first a note to Bob that his link points to a 46-1209. I checked the schematic for your 46-1201 and found two versions so I'm assuming yours is the one with the 50A5 and 35Y4. First off, determine if the hum is controlled by the volume control or is it constant no matter where the volume control is. Now the schematic I'm looking at has no coupling capacitor from the volume control to the grid of the first audio amp. There should be a .01mfd cap. Lots of hum if you don't put it in. It's very easy to install the power supply filter capacitor negative leads to chassis ground where, in this case, they should be connected to the B- bus (voice of experience). You will get a loud hum if connected to the chassis. Check to see if it hums in phono mode or radio mode. That should get you in the right direction .
Welcome to the Phorum. But first a note to Bob that his link points to a 46-1209. I checked the schematic for your 46-1201 and found two versions so I'm assuming yours is the one with the 50A5 and 35Y4. First off, determine if the hum is controlled by the volume control or is it constant no matter where the volume control is. Now the schematic I'm looking at has no coupling capacitor from the volume control to the grid of the first audio amp. There should be a .01mfd cap. Lots of hum if you don't put it in. It's very easy to install the power supply filter capacitor negative leads to chassis ground where, in this case, they should be connected to the B- bus (voice of experience). You will get a loud hum if connected to the chassis. Check to see if it hums in phono mode or radio mode. That should get you in the right direction .
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
