In the majority of cases, crossover failures involve the capacitors and generally electrolytic caps. I used to mod Dahlquist’s DQ-10s (mirror image/swap Piezos for ribbons/etc) in my shoppe(talking 1980’s here). I never have seen a stock DQ-10, with anything other than Metalized Mylar caps. Look at the crossovers and if the caps have a shiny yellow wrap, they are probably stock, and still good.