More on the Dallas IC up-grade.
I powered up the 2465B again today and all appears well, so the FM16W08 appears to be holding its memory. But, just in case, I ordered a spare DS1225AD today to copy the scopes cal data to and then put it in storage, just in case. I have a spare FM16W08 and adapter board that I'll do the same with. AT this point, it's cheap & easy backup. Then if we get hit with an EMP or a super solar storm, maybe one will survive, assuming the rest of the scope makes it.
DSO - I think there may be some confusion about the data retention of the FM16W08. See data below. The 10 years at 85 Deg. C is hot. At 65 Deg. C (that's 149 F) the data retention is 151 years - according to the Cypress data sheet. So, if I keep it below 75 F, it might even out live us.
There was a concern of shorting the pins on the Dallas DS1225Y when removing it. But after looking at the expanded diagram of that IC posted by Holden, I concluded that if they were momentarily shorted, it would be through high impedance paths. So the battery should survive that. And I used the smallest tip on the vacuum desolder tool, so I don't think they ever shorted.
After removing the DS1225Y, I was about to plug it into a conductive piece of black foam, but then had second thoughts about it discharging the battery through possible high impedance paths via. the foam. But, then while looking up DSO's concern about the IC's life, I found where the data sheet seems to think it's not a problem - if I understand it correctly. So, you're probably right - not a problem.
Also, for the sake of science, I want to excavate through the top of the old IC to the battery, to measure the remaining voltage. If done right, the IC will not be functionally harmed.
DSO - When using my vacuum desolder tool, most of the pins desoldered ok. But half dozen or so pins were a challenge. It just would not pull all the solder out. Even turned the board upside down to get help from gravity. Cleaned the tip orifice, but it was clear and the vacuum was working at the tip. Since this is my first real application with it, I wanted to ask what temp you had yours set to? This one was set to 300 C. Another possibility was, the tip might be too small to transfer enough heat through the multi-layer board.
Below are photos of the board before and after replacing the Dallas memory IC.