05-09-2010, 06:08 PM
Hi Vinzer,
Have you made any basic voltage checks in the audio section?
If the audio output is not negative biased enough, excessive current draw will result. This can overload the power supply and result in hum. And distortion will follow too. Would expect to see at least -15 volts on the control grid of the 42 tube for normal class A operation. Would also verify all the tube pin voltages including those on the 2nd detector tube. Hope this helps.
Richard
Have you made any basic voltage checks in the audio section?
If the audio output is not negative biased enough, excessive current draw will result. This can overload the power supply and result in hum. And distortion will follow too. Would expect to see at least -15 volts on the control grid of the 42 tube for normal class A operation. Would also verify all the tube pin voltages including those on the 2nd detector tube. Hope this helps.
Richard
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
