The Microprocessor is not reciving the proper sequence of pulse's from the cassette mechanism and not allowing the unit to work.  It could be a simple belt, mode switch, cassette down switch, cassette loader mechanism switch,PG pulse on the main head cylinder, or the FG pulse on the capstain motor.  It is shutting down so the tapoe does not get damaged.  Im sorry to tell you that most likly this will exceed the cost of a new unit to have it serviced and repaired.  Let us know how you made out.  Good Luck

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