KiT 6550 Hum

[TimN]

Originally Posted by bob orbell

Hi Tim, without reading through the complete thread, do you have the balancing resistors fitted to the 5U4 rectifier valves, as in the FAQ? how old are the 5U4 valves ? one may be working harder than the other, I doubt you will totally remove all hum due to the heater voltage being AC but the hum should be very low level indeed, I found that changing C5 to 82uF on mine almost totally removed hum. Bob

Thanks Bob. It's had the resistor mod, but I can try new valves and a C5.