01-15-2024, 07:57 PM
Thanks for the assistance. I don't think it is interference coming in the power supply. I have worked hard to quieten the shack and I am not hearing it in other radios. The radio has had some modifying done in a pretty crummy way. I have rewored the entire power supply.
I replaced the multi filter cap with one from Hayseed Hamfest . The noise seems to be coming from ahead of the volume control as it is relatively quire with the volume center tap disconected. Only slight 60Hz hum as you would expect in a single ended amplifier.
The antenna input has been messed with. The BNC antenna connector has nothing connected to the center pin and a strap conncted from the chassis to the other pin. The screw terminal 2 connector strip antenna connector does not have a chassis connection. It ties to the B minus bus and the other side to the RF front end. I got a nice shock from the antenns "hot" terminal on the antenna screw terminal and chassis ground. Something is miswired in the front end.
I have two of these radios in good cosmetic condition. I may repair this one as designed. The other one I may modify with a power transformer and a full wave solid state rectifier removing the 35W4 and replacing the 50C5 with a different power tube. I have a hammond power transformer with a 250 volt center tap and 6.3 volts at 2 amps. I also have a small 50 mA 7 H choke that will fit.
Should be a fun project and not all that difficult as the radio has a B minus bus rather than a hot chassis. Withe a 6AQ5 or 6AS5 I have the needed heater capacity.
I replaced the multi filter cap with one from Hayseed Hamfest . The noise seems to be coming from ahead of the volume control as it is relatively quire with the volume center tap disconected. Only slight 60Hz hum as you would expect in a single ended amplifier.
The antenna input has been messed with. The BNC antenna connector has nothing connected to the center pin and a strap conncted from the chassis to the other pin. The screw terminal 2 connector strip antenna connector does not have a chassis connection. It ties to the B minus bus and the other side to the RF front end. I got a nice shock from the antenns "hot" terminal on the antenna screw terminal and chassis ground. Something is miswired in the front end.
I have two of these radios in good cosmetic condition. I may repair this one as designed. The other one I may modify with a power transformer and a full wave solid state rectifier removing the 35W4 and replacing the 50C5 with a different power tube. I have a hammond power transformer with a 250 volt center tap and 6.3 volts at 2 amps. I also have a small 50 mA 7 H choke that will fit.
Should be a fun project and not all that difficult as the radio has a B minus bus rather than a hot chassis. Withe a 6AQ5 or 6AS5 I have the needed heater capacity.
