We have a Tek 2440 Scope in lab that fails "4000-FPP" for battery. It checks out for cal otherwise. We opened the unit and found a jumper in place of that battery (that looks factory done).
I'm wondering if either someone swapped a board between two different scopes, or is this a glitch in the self-test based on a memory update (i.e.: newer memory chips don't require the battery).
We haven't found it addressed in any manuals; but wondering if anyone here may happen to know about this issue.
If I mis-remember correctly, the ROM chips have the battery built in, and I think it is serial number dependent. I recall this problem about 9 or so years ago with a customer. We were able to get replacements and the problem cleared up. But, I think we got the last of Tektronix bits then, and they no longer support it.
There should be two chips on the top board that are approx. 3 times thicker than normal..those are the chips with built in batteries (designed obsolescence).
I don't think they're available any longer, so, you may advise your customer to upgrade to a new TDS model, which will at least be supported for another year or two.
Hope this helps,
Mike