My oscilloscope has a diagnostic error+ E5331 or E5332.. What does this indicate?

My oscilloscope has a diagnostic error+ E5331 or E5332.. What does this indicate?

These diagnostic error codes indicate a problem with communication between the MMU (Memory Management Unit) and the Timebase controller (Timebase Control – MMU Handshake Control, U760).

Due to the age of these products, replacement parts are no longer available. Repairs on these products are available from Tektronix Service on a best effort basis.