Just last night I repaired my 817ND that had the same problem. Turned out to be an open PCB trace. Bridged the trace and it's operating fine now. An ohmmeter and magnifying glass are your friends in troubleshooting and repairing this one.
As luck would have it, I stumbled across this link AFTER troubleshooting and repairing my rig. heh.
Good luck and let us know how you make out with this.
73, Jeff WN1MB
Jeff WN1MB