I am getting the diagnostic error E5622 on my 11800. What does this indicate?

I am getting the diagnostic error E5622 on my 11800. What does this indicate?

The error code indicates a communication problem with the Time Base Board and is usually caused by dead NVRAM batteries.  There are two NVRAM chips on this board and they plug into a socket that has control and battery capabilities.  When the batteries go dead you loose the Enhanced Accuracy Calibration data and receive this error message.

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.