Hello 1st time builder here. I have built amplifiers and microphones with great success so I know how to use an iron. I'm going through the setup guide, at step 5 all the voltages check out within tolerance. Step 6 I get the sine source going and adjusted to 2 VAC. When I engage the unit 0 V. I can confirm listening to the audio I hear it then engage the unit, no sound. Voltages at TP1 .999, TP2 .008, TP3 1.002. Any help is appreciated!