I was given a very nice late model Swan MKII, I have an early 3-400 one that I have been using since the 80's. I built a PC board and replaced the caps, bleeders, diodes in the power supply. Although the Eimac 3-500's look great one has no output, filaments are fine but no high voltage. My question is I have an extra 3-400 that is good, of course the 3-400's are 0 bias and the later Swan has bias added for the 3-500's. Rather than purchase a new 3-500 what ill effects would happen if I ran the 3-400 with bias added with the 3-500?