I remember having some issues similar to this before I sent my deck to Paul at Pro Digital. You might give him a shout and see what their long distance prognosis is.
Depending on what his estimate is cost wise, you might be better off replacing the unit. In fact, PM me if the cost it too high. I have 3 decks (Sony 75 ES, R300, and 670) I'd be willing to let 2 of them go since I'm no longer using DATs.
Take Care,
Wayne