HP41 post replacement experiment

[Bruce Larrabee]

I really liked the brass replacement posts for the HP41 posted by aj04062.

I have made some posts out of Delrin. Which I am about to test out.

Here is a picture of the first one.

[Reth]

I'd be very interested - having at least 3 units with broken posts. I have missed the other solution you mention, link?

Cheers,

[Bruce Larrabee]

The brass posts are shown at:

file:///E:/Documents%20and%20Settings/Zorro/My%20Documents/HP/HP41/repair-posts-1.htm

[Geir Isene]

Diameter?

[aj04062]

Diameter would be .156 OD. .187 OD will work too, but gets very close to through hole plating and this is used on the upper posts. Now we just need a reliable way to repair the back case holes that hold the battery contact in. I've been toying with the idea of glueing the contact to the case and then using short (.25) screws to attach it to the post. Other suggestions?

Aluminum standoffs from Keystone Electronics Corp PN 1801B, Mouser PN 534-1801B

2-56 x .25 lg Pan Head screw, Mouser PN 534-9355

2-56 x .75 lg Pan Head screw, Mouser PN 534-9357

Edited: 11 July 2012, 8:06 p.m.

[Geir Isene]

Where to buy? TAS?

[aj04062]

Geir,
I could sell you some, or you could buy from Mouser.com. Use the part numbers above. You'll probably pay more in shipping than the parts as they are not that much.

[Geir Isene]

I'll happily buy from you. Paypal? E-mail me at: g @ isene . com

Some baby-step instructions to follow would be excellent.

BTW; I need to repair three calcs.

[Reth]

Quote:

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I'll happily buy from you. Paypal? E-mail me at: g @ isene . com

Some baby-step instructions to follow would be excellent.

BTW; I need to repair three calcs.

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I double this :)

[Basil]

I think that the brass replacement posts for the HP41 done by aj04062 was one of the better ones I’ve seen. And I guess that everyone on this forum would appreciate if those “baby step instructions” were posted here on this forum.

[aj04062]

I'll get an article together soon. Initially I may have to describe in words the "baby" steps as I do not have pictures of the steps, but could amend the procedure the next time I repair a unit.

Adam

[aj04062]

Article Posted

[Geir Isene]

Nice - I am looking forward to receiving the post+screws and see if I am able to not butcher the calc and turn it into a more solid 41CL.

[Basil]

Well done! Thanks.

[Bruce Larrabee]

Hello Everyone,

Well the Delrin posts seem to be working quite well so far.

Here are my final specs for this case, a HP41C tall key model with the tall cylindrical extrusions inside the case back lower section.

Delrin posts:

0.176" dia. 0.250" length, drilled and threaded all the way through for 4-40 NC screws

Post holes milled out to about 0.065" deep

4-40 NC Brass screws shortened to about 0.200" of thread. Heads turned
down to 0.160" dia.

Tried epoxy first but one failed. Tried super glue next to much better effect.

I trimmed about 0.010" off the top of the posts to achieve the final fit between case, motherboard, elastomeric connector and keypad board.