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HP Forum Archive 20

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HP-41 Permanent broken Post Fix
Message #1 Posted by aj04062 on 17 May 2011, 10:35 p.m.

Up for review is my permanent repair to fix your ailing 41.

As some in the forum know, I had posted the question why my two 41CVs were acting strangely. POSTS. Nothing more, nothing less. Well the following is my permanent cure for one. It's posts where helplessly cracked beyond repair. What I resorted to were two 4-40 brass standoffs about .25-.27 inches long x .1875 OD.

Finished height above board = .200

The old post was milled off with a .1875 end mill and bored down about the thickness of the board (.070)

They were then epoxied into place.

Now proper torque can be applied to the 4-40 screws and the unit behaves as it should. Hopefully it will last another 29 years!

Edited: 17 May 2011, 10:49 p.m.

      
Re: HP-41 Permanent broken Post Fix
Message #2 Posted by db (martinez, ca.) on 17 May 2011, 11:54 p.m.,
in response to message #1 by aj04062

That's a very elegant solution. I just lazy out and slip slightly too-tight springs over the split plastic. It works but not as prettily as your brass fittings.

            
Re: HP-41 Permanent broken Post Fix
Message #3 Posted by aj04062 on 18 May 2011, 6:04 a.m.,
in response to message #2 by db (martinez, ca.)

These ones were shattered and sheared off at the board. No spring would have helped them!

      
Re: HP-41 Permanent broken Post Fix
Message #4 Posted by Angel Martin on 18 May 2011, 1:46 a.m.,
in response to message #1 by aj04062

Brilliant solution, and great pics!

      
Re: HP-41 Permanent broken Post Fix
Message #5 Posted by Didier Lachieze on 18 May 2011, 2:11 a.m.,
in response to message #1 by aj04062

Great solution! Would you have some spare standoffs as I just have one 41C with the exact same problem?

            
Re: HP-41 Permanent broken Post Fix
Message #6 Posted by aj04062 on 18 May 2011, 6:03 a.m.,
in response to message #5 by Didier Lachieze

I should have a few next week. I requested a sample lot from Keystone Electronics. They will need to be faced back from their .375 length to .25-.27. Drop me an email off-line for info.

                  
Re: HP-41 Permanent broken Post Fix
Message #7 Posted by Monte Dalrymple on 18 May 2011, 9:53 a.m.,
in response to message #6 by aj04062

Excellent solution. I've got a couple of machines that can use this fix. But isn't the .1875 OD a little too big for the holes in the processor board? I thought that the posts were 4.3mm (0.169) and the holes in the processor boards were 4.5mm (0.177). Did you have to slightly enlarge the holes in the processor board?

Monte

                  
Re: HP-41 Permanent broken Post Fix
Message #8 Posted by PeterP on 18 May 2011, 10:22 a.m.,
in response to message #6 by aj04062

aj, can you post a link with what exactly you ordered, I think there might be a few people (including myself) that want to try your truly elegant and well working solution.

Thanks!

Peter

                        
Re: HP-41 Permanent broken Post Fix
Message #9 Posted by Raymond Del Tondo on 18 May 2011, 12:04 p.m.,
in response to message #8 by PeterP

I'm interested in a couple of these brass cylinders, too.

Are these available in the suitable legth for the upper posts, too?

Is the screw thread already there?

Thanks

Ray


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