I want to bring my HP41CV back into use. With new batteries in it will not operate. No visual problems with on rocker switch. I s this a common fault. Any useful advice gratefully received

Most of the time, problems with the HP41 series are due to bad internal contacts.

The battery pack and modules connect to a flexible PCB that's held against the keyboard PCB by a strip of foam and the screws that hold the case together. The 'Fullnut' machines have a separate logic PCB that's connected to the keyboard by a zebra-strip type of connector, again clamped by the case screws.

If you are happy working on static-sensitive electronics, you could open it up (take out the battery pack, peel off the feet, the screws are under them) then clean the contacts with propan-2-ol (isopropanol, isopropyl alcohol). When reassembling, do not overtighten the screws, if you strip the thread in the top case, you will have a lot of work to do.

My experience is HP-41s usually only needs to be reset. For some reason, starting one up after a long "vacation" does not do this simply by putting in new batteries. I've even had a "returnee" go on strike when I connected the card reader for the first time. Seems once they know you will be using them a while, they do quite well - I guess we hurt their feelings by ignoring them for so long. Seems HP had AI 25-yrs ago and didn't really know it!

Refer to your Owners Manual; My CV Manual on pg 242 says:
"...#3 While holding down the <- key (the correction key) turn the calculator ON. This is a "master clear" and the entire calculator will be cleared."

This is also described near the bottom of pg 23 in the paragraph ending with the blue MEMORY LOST.

Hopefully this will do it for you and you won't have to give your CV a frontal lobotomy - just a swift kick!

Bob