To Repair, or Not Repair, My 41CV Again

[Chumango]

I bought a used Full Nut HP-41CV in 1983. It got me through college and many years as a practicing chemical engineer. It was my only calculator until a couple of years ago when it finally quit working - I could not turn it on.

I looked around and found the 35S and the DM41X, and got them. Then I found ways to fix my 41CV - I took the case apart, did not observe anything wrong, and reassembled it. It worked again!

Then the divide key got mushy, and I had to press hard to get it to register. Looking around, I heard of something that might help - Craig Deoxit. I opened the case again and applied Deoxit to the tiny hole above the offending key. I carefully inspected the posts with a light and a magnifying glass, and three of the four were cracked, one quite badly (the upper post on the side opposite the on/off key). I applied super glue to the inside of the posts hoping it would give something for the screws to grab.

Both of the support pads on the back case - where the screws snug up - were broken off. I glued one back in place, but I was unable to find the other. I cut a piece of plastic to the right size and glued it in place and drilled a hole for the screw.

After I put it back together - nothing. I can't turn it on.

So, should I go ahead and get the replacement posts and attempt repair again? It would mean additional surgery. Or should I just chalk it up to an old calculator finally giving up? For reference, I have the 41 repair book from The Calculator Store.

A concern I have is, what if the divide key still does not work? It might not have been a post problem. That key feels different from the other keys now, it did not before. I'd hate to go through the trouble and expense of doing this to find that such an important key does not work.

I do have my father's 41C that is fully functional, and others as well (42S, 32SII, 15C CE) but this 41CV has sentimental value to me.

[johnb]

(03-07-2024 06:33 PM)Chumango Wrote:  So, should I go ahead and get the replacement posts and attempt repair again? It would mean additional surgery. Or should I just chalk it up to an old calculator finally giving up? For reference, I have the 41 repair book from The Calculator Store.

A concern I have is, what if the divide key still does not work? It might not have been a post problem. That key feels different from the other keys now, it did not before. I'd hate to go through the trouble and expense of doing this to find that such an important key does not work.

I do have my father's 41C that is fully functional, and others as well (42S, 32SII, 15C CE) but this 41CV has sentimental value to me.

Before deciding, I would ask myself the following questions:

1. What are you going to do if you don't try a repair again?
   
   1. stick it in a drawer or a glass case and cherish it forever even though it doesn't work?
   2. sell it or give it away?
      
2. How much trouble and expense do you think it will be?
3. How much might it cost to get someone else to repair it?
4. Would it be cost-effective to sell it and buy another just like it?
   (That would certainly be easier but the new 41CV wouldn't be the one that got you through school and so many years of your career.)
   

Personally, besides asking myself those questions I would also re-read the book in its entirety, then take a deep breath and -- slowly, carefully -- re-inspect the unit to see if there's anything that I had missed.

Then I'd decide what to do.

[Allen]

@johnb, very nicely put!

HP 41 Post repair is surprisingly quantum in nature. The very act of (re)opening these brittle beauties can actually cause the failure you were hoping to inspect, and avoid!

I still have my first HP calculator on the shelf behind me, but seldom use it, preferring instead to use one of no particular sentimental value for daily calculations.

Perhaps it would be a fitting retirement (bypassing the postmortem autopsy) to buy a small stand or display - perfect for bookshelves or office cabinets - and remember your trusty 41 as it was it the "old days"?