Find out what mods your client absolutely needs to keep and remove the rest. Right now your best tools would be a tone generator and contact type signal tracer
like you’d find here https://www.amazon.com/dp/B000FTADX0?aaxitk=9mebOhyw2K.DO1dFSxs3NA&pd_rd_i=B000FTADX0&hsa_cr_id=4435739830101
There are cheaper ones than this, but don’t go too cheap as the tracers especially are less reliable.
From: Robert Chrysafis [mailto:email@example.com]
so i hooked up a mic through a dbx 286 both confirmed working even tried different wiring between mic and dbx and punch block. i can't seem to confirm via meter movement that
board is passing audio. i did add a line to mic level pad so i don't blow the mic channel inputs and i did jumper the prefader i/o on cn3 terminal. also the board has some mods pictured here