I biased the FET using the listening method and was able to find the sweet spot fairly easily. I measured 11.5v at the FET drain after I had found this spot. The mic does pass signal, but is very noisy with random popping. Turning on the pad or high pass has no effect on the pops. If I tweak R11 past the sweet spot so that I measure >26v at the drain, the pops disappear. The noise floor is still very high though. Also, when the drain voltage is set to 11.5v, I only have 11v at the zener. When R11 is set too high, the zener voltage is correct. I have cleaned both sides of the board with isopropyl alcohol and toothbrush. I did not use styrene caps for this build. Is the transistor shot, or is there a problem with one of the components?