Repairing HP 41C screw posts



#2

Hello all,

I have a beloved Hp-41CX who eventually suffered the unavoidable fate of its screw posts breaking after years of pressure.
I need help and techniques to solve the problem, please help.

Thanks in advance,

Fouad


#3

Search the archives. Look back many years--early 2000s. Look fr names such as Vieira, Luiz C. (Brazil)

I hope that helps.

Edited: 25 Sept 2011, 9:58 a.m.

#4

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=2


#5

Quote:
http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=2

I wish we could pull that from the archives. Some really bad ideas in there.

1) *Never* use cyanoacrylates for plastic repair on HP's, especially on screw posts. Styrene plastic welding solvent only. Replace 1/4" screws with 3/8" screws on the lower posts. #2 sheet metal screws work okay, tri-lobular plastic screws are best but very hard to find in small quantities. #2 metal screws are available in hobby shops.

2) *Never* use the described method to attach the logic board to keyboard. You might as well just throw it away now if that is your plan.


#6

Hi Randy,

Maybe Dave can let you put red pen glosses on it:-)

It is a probem--propagation of bad ideas.

Maybe an edited version should be entered in the Archives.

#7

I just repaired one replacing the broken post on the CPU end with a metal standoff. I cut off the broken post near the back of the keyboard and threaded the standoff into the remaining hole. I then chucked the standoff in a drill and filed it down to fit the hole in the CPU board, and adjusted the length of the screw on the bottom and the height of the standoff. Result another great working CX. I have also read that others have glued in metal posts using epoxy.

#8

I got great results by slipping a spring over the split post to keep it together and usable. This has the added advantage of being able to slip the coil connector (and spring) off in the future. The glue and wire-wrap method works fine though.


#9

Quote:
I got great results by slipping a spring over the split post to keep it together and usable. This has the added advantage of being able to slip the coil connector (and spring) off in the future. The glue and wire-wrap method works fine though.

While the wire-wrap method works, a card-reader o-ring makes a great clamp while the solvent cures.

That said, I really don't understand all the angst over cracked posts as longer screws (3/8") fix 95% of the issues with lower posts on the 41. We beat this to death, IIRC, back in 2003/4. A cracked post is no big deal if the 1/4" screw is discarded and replaced with 3/8". HP did this as a production change in about 1983 and on all 41's that were received for service.

A post that has sheared off can usually be repaired with little drama if all the pieces are there. Styrene plastic welding solvent puts it back together, leave overnight to cure and a 3/8" screw completes the job.


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