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8648 Series Backup Battery Questions-What is it for?

Question asked by sreaves on Jan 29, 2016
Latest reply on Feb 3, 2016 by sreaves

The 2/3A Lithium Back up battery in my 8648D is dead. I did not have one handy so I wired in a CR series coin cell. When I powered up the unit the first time it restored the CAL data, On occasion on power up it shows the 503 message for restoring the attenuator cal data (I am assuming from EEPROM, It appears to be in cal but the message is annoying.

I am guessing that the battery I used may not be enough voltage to keep the memory backed up and it is just restoring the data as needed. I plan to order and install the correct one but I would like to know why HP did not just get the cal data from the EEPROM.

Does anyone know exactly what this battery actually backs up and why the unit runs the cal data out of SRAM. Is it because of speed?

Any Keysight/HP employees that worked on these generators that can enlighten me as to the design/function of the product?
Any CLIPS or detailed data out there? Since these have been out of support for some years they are showing up on the surplus market and are wonderful generators for the amateur radio (ham) workbench. It would be wonderful if Keysight would release the full schematics and details of the 8648 series.