08-13-2014, 07:18 PM
Do you have the grid cap wire of the 75 routed inside its tube shield?
If the wire is outside the shield it will pick up the electrostatic field generated by the plate of the 42 output tube, producing positive feedback and oscillation.
I had this exact problem with my 60 until I rerouted the grid wire inside the shield.
If the wire is outside the shield it will pick up the electrostatic field generated by the plate of the 42 output tube, producing positive feedback and oscillation.
I had this exact problem with my 60 until I rerouted the grid wire inside the shield.
