The Museum of HP Calculators

HP Forum Archive 17

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HP41CV Dead
Message #1 Posted by colhind on 15 June 2007, 11:52 p.m.

I have an HP41CV that was stored for about four years with battery left in it. I recently decided to resurrect it but find that I cannot breath any life into it. It was working when stored but is now as dead as an Auk.

I also have another 41 that works fine so I tried swapping bits back and forth to determine which part is faulty. It turns out that everything in it works except the keyboard/display unit.

In other words the problem isn't related to any of the usual things like crook battery contacts, poor contact between the printed circuit boards, etc. It would appear that something on the display/keyboard unit has died in its sleep. Either that or there is something that needs to be reset.

Any ideas will be greatly appreciated.

Cheers, Ron

Re: HP41CV Dead
Message #2 Posted by Ralph on 16 June 2007, 8:12 p.m.,
in response to message #1 by colhind

I had a 41C expire many years ago. I didn't store it with batteries but I did store it in a hand made leather case my Uncle made for it. The leather dyes and chemicals and the humidity in the pouch destroyed the flimsy interface gizmo between the boards. For a while I had it running with a crude solder job but the wires were too big and stiff for the task at hand. Check the board interface for clean contacts and that the coil assembly is not damaged. I can't recall the proper name for the little thing.

also check the mount posts to see that they are not broken. Then the boards won't make contact either.

Re: HP41CV Dead
Message #3 Posted by colhind on 20 June 2007, 2:42 a.m.,
in response to message #2 by Ralph

Thanks for the tip.

Sadly, deterioration of the conductive strip connecting the two boards isn't the problem. I wish it was for I would rapidly solve it with my trusty soldering iron and a few strands of enamelled wire. No; by a process of elimination I have found that whatever the problem is, it is related to the keyboard/display printed circuit board.

I set out to try to awaken it by means of operating the card reader but alas I cannot try that until I fix the confounded drive wheel which I now find has turned to mush. Now where did I put those little O rings?

Anyroad I am still hoping for suggestions.

Cheers, Ron

Re: HP41CV Dead
Message #4 Posted by Marco Schriek on 4 July 2007, 4:36 p.m.,
in response to message #3 by colhind

Maybe a stupid question but how do you open a HP41CV? My 2-key is playing tricks with me and I want to clean the calculator on the inside. My HP41CV is about 26 years old and still working pretty good until some month ago. The problem is getting worse. Any suggestions.

Re: HP41CV Dead
Message #5 Posted by Randy on 4 July 2007, 7:01 p.m.,
in response to message #4 by Marco Schriek

Remove the four rubber feet. Be careful when peeling them off, they have two layers. Make sure you get both layers together or they will not stick again. Remove the four phillips screws that appeared under the feet. Lift off the rear cover. On Fullnuts, lift off the logic board and then the battery shield.

Another specific Fullnut issue: Later units have two 0.015" white teflon washers on the lower posts. If your unit has them, don't loose them! They go on top of the logic board.

Cleaning intermittent 41 keys

If you remove the battery/port connection block from the case bottom, be sure to remove the four port covers or modules first. Removing the block with covers in place can tear the thin conductive foil.

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