Need to completely connect the amplifier assembly. No speakers or load. Find TP 305 on the PAA. Measure for any DC voltage at that TP. Connect your black test lead to the metal chassis ( ground ). Probe the TP with your red test lead.. Be very careful not to short out that TP to anything. If you don't have mini-grabbers for your meter. Wrap some tape around the test probes metal tip leaving just the very end exposed. Heatshrink tubing works very good as well.