Thanks Colter.
Bobby, I'd put enough signal out of your amp to get a decent bounce in your needle when you measure AC voltage exiting your amp (Red probe to Red out, or positive; Black probe to Black out, or negative). When I say "signal" I just used a current pop tune with a lot of fluctuations at all frequencies, that way I'm going to get a good oscillation no matter where I am on the crossover circuit, high or low freqs. I also have a clip to attach on the end of the probes so that I could clip the black probe to the -HF in.
Verify signal across +HIN / -HIN.
Leaving one probe (black) on the -HIN, proceed through your circuit with the other probe (red). from each component to the next, checking for the voltage fluctuations before and after each component.
The place where your voltage disappears is highly suspect - that component, or solder, is where I'd begin your further testing.
Being firm here is, IMO, okay - I'd use that red probe to press on the solder joints, to see if they're loose. I got lucky in that I pressed hard enough to expose a loose solder joint *purely by accident*.
When you do find that disappearance in voltage, I'd suspect the joint where you located the disappearance, and the component before that joint, and the joint before that joint, and the joint after that joint. That's a lot of joints.....
I.e. if your troubleshooting went like this: +HIN (okay) .... joint to transformer (okay) .... joint after transformer (okay) .... joint to capacitor (okay) .... joint after capacitor (NO VOLTAGE HERE) ....
then I would suspect the joint after the capacitor, the capacitor itself, and the joint before the capacitor. check those solders and components for proper values and use resistivity to check continuity.
Note: You could also use pink noise, or a tone track, if you know the tone you're working with should propagate through the "side" of the crossover you're testing.
Best luck. Post how it goes for you....