Hi folks,

I have an HP 54501A, and I left it unpowered for months on end, then when I turned it on again, it lost its calibration data. Problem is, I can calibrate it but after turning it off it loses it again.

Sounds like the internal battery is dead, but I don't know where exactly it is located. It's probably inside a chip. Does anyone have experience with these scopes?

 

http://www.instructables.com/id/HP-54501A-NVRAM-Replacement/

 

Interesting and great reply! Who knew?
@MathematicianKing
As noted in the instructables comments, I would avoid an eBay clone and stick to a genuine Maxim part from a franchised distributor. These are hybrid modules and the RAM is selected for very low standby current. Who knows what the clones have? Even with Maxim, once these are powered up the battery backup is turned ON. Pulls from old boards are not likely to have a long remaining life. Beyond that, these are great little parts.