I've been reading about various mods found on the 'net. I'm going to try the 6GM6 RF swap. About the mod for removing B+ from the filter in the 75A-3 (which I understand Collins implemented in the A-4); I'm wondering what they found that made them change the design. Are there any risks to leaving this alone on my A-3 (I plan to use it frequently). I have the 6kHz and 3.1 kHz filters, if that matters.