There is no joy in Mudville this evening. I took the unit out again this afternoon for a test after coiling the extra lead as suggested and resetting back to factory default and if anything, the playback is worse. I even moved to the stern seat to be sure the 'ducer was fully under water and tried things while moving both directions.
I have only one other thing to try and that is not plugging it in to the portable setup that my 570 was using. I'll mount the new base somehow and plug the transducer cable direct to that mount although I doubt the portable mount is the problem.

Bummer...............