I agree, it's already getting daft :>)
It's a simple low pass filter with a single inductor and cap on the LF, the rest of the circuit is for the HF. Check each line in turn for continuity from input to output. Work your way back towards the input with one lead of the meter. If need be, test the actual PCB traces for a possible crack by scraping a smidge of resist off etc. It's not uncommon to crack the board around an inductor mount/ tie wrap etc when the cabinet is banged around. Bose and H&H/ Fane setups etc sometimes use polyfuses for protection as well as lamps, but I don't see any on your board, just the lamps. Lansing generally mark their protection lamps with a dot of coloured paint, so if they have failed, replace both at the same time with the correct ones. They are available from JBL, but you need to tell em what colour the dot is.