Bill,
I may be missing something in the interpretation of what you have said regarding the recorder output being pulled high and all of your measurements showing other parts of the unit being OK. Is there an op amp being used as a buffer driving the recorder output? Could it be defective? From the voltage you are seeing it sounds like an op amp is bad with its output pulling against the positive rail.
I don¡¯t have a schematic of that particular instrument so am merely drawing a conjecture.
Greg
