05-04-2018, 01:22 AM
Hi;
There is a 10 uf cap between the B+ and the chassis, which is also connected to A-, this is an electrolytic cap, and if it's dried out the set will hum whilst running it off of a power supply, I don't know if the same is true on batteries. It should be replaced anyhow because if it shorts out it could damage the tubes, it isn't likely but may happen. Use at least a 100 volt cap here as it has 80 vdc across it. If this isn't the issue then the power supply may have a fault, or may need a capacitor to filter the power line.
Regards
Arran
There is a 10 uf cap between the B+ and the chassis, which is also connected to A-, this is an electrolytic cap, and if it's dried out the set will hum whilst running it off of a power supply, I don't know if the same is true on batteries. It should be replaced anyhow because if it shorts out it could damage the tubes, it isn't likely but may happen. Use at least a 100 volt cap here as it has 80 vdc across it. If this isn't the issue then the power supply may have a fault, or may need a capacitor to filter the power line.
Regards
Arran
