1998 Mercury Villager speedometer problem

Speedometer quit working.

First replaced speed sensor (later verified old one was still working). Replaced instrument cluster (with one from salvage yard. Still no speed registering.
All other guages work fine including the tachometer (Does it also receive its signal from the speed sensor?). I haven't seen any fuses associated with the speedometer but was wondering if I had missed something there. I am at a loss as to what to look for next other than see if I can find the wires going to the speedometer and check for continuity there and at the speed sensor. Would appreciate any help, I'm going broke replacing parts (not to mention buying gas)!