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Killed my 41-CX Halfnut - Printable Version

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Killed my 41-CX Halfnut - aj04062 - 07-09-2012

My on & User key was acting flaky (sticking on) so I disassembled and cleaned with some alcohol. I then puffed it with some canned air to dry out and now the unit is dead.

Could I have shorted and fried something doing this?


Re: Killed my 41-CX Halfnut - Randy - 07-09-2012

Probably not, halfnuts are pretty tough. Try shorting the bigger electrolytic cap for a second or two (without power present) to reset continuous memory. They seem to lock up easier than fullnut boards.

Re: Killed my 41-CX Halfnut - Luiz C. Vieira (Brazil) - 07-09-2012


Adding some extra advice to Randy's perfect ones, make sure no screw posts are broken and/or the screw basis, the ones with the small holes in the lower case. If the half cases are not tighten up with each other, power contacts in the IO/Battery assembly will not properly make contact with the mainboard.

Never enough to ask: are batteries in correct orientation?


Luiz (Brazil)

Re: Killed my 41-CX Halfnut - aurelio - 07-10-2012

I should call the POLICE and ask send immediately a patrol to the
killer......... =:)

Ciao Luiz, I think that aj04062 is a high expert of broken posts issues, a skilled people (he wrote here a post about permanent broken post fix patented by him ...compliments againa nd thanks!)

So that I'm pretty sure the first check he did was the tightening of the screws...after the batterie's correct plug-into =:)

I hope success with the fixing of this problem and forgive me, please for my humor..


Edited: 10 July 2012, 8:16 a.m.

Re: Killed my 41-CX Halfnut - Luiz C. Vieira (Brazil) - 07-10-2012

Ciao, Aurelio!

he wrote here a post about permanent broken post fix patented by him...
You mean the one with metal/brass finishment? Yep, I remember it quite well, thanks! Very good solution!

There is also another issue, though. After dealing with some HP41's as for repair and daily use (no hacking), I noticed that in some IO/battery assembly, the foam bar that is used to press the contacts against the mainboard was replaced by a solid, instead flexible piece of what seems to be a silicon-based rubber bar. The foam bar becomes soft after some time and the contacts are no longer efficient even if the posts are OK and both cases are tighten closed.


Luiz (Brazil)

Re: Killed my 41-CX Halfnut - Richard Wagoner - 07-10-2012

Also - don't forget to check the orientation of the 'case space' taht 'U' shaped plastic doo-dad that fits between the top and bottom cases.

If it is upside down the cases will appear to mate but insufficient pressure is exerted on the CPU board and it will not make good contact with the key/mother board,


PS - good luck!

Re: Killed my 41-CX Halfnut - aj04062 - 07-10-2012


I have tinkered with those new posts. I have since found some ALUMINUM standoffs with smaller screws (#4) so I don't have to mess with the case. Standard pan head #4 screws fit the hole and recess nicely!

I should probably write-up an article with pictures and PNS from the electronics websites.

I tinkered some more, base on everyone's suggestions, with no luck. It is very odd.

Re: Killed my 41-CX Halfnut - Luiz C. Vieira (Brazil) - 07-10-2012


That would be great! Broken plastic posts will always be an issue...

About your halfnut: is it assembled already? Chances are you have already seen this picture, and in this case, you can see where did I connected an external 6Vcc battery pack (black for negative and red for positive, the ones going to bottom, not the red one going to the left) while performing some tests with this 'somehow dead' 41 halfnut. In fact, the little thing was alive after being disassembled and reassembled. I guess it was just some bad contact somewhere, and after soldering it all, it got back to business.

Hope you succeed.

Luiz (Brazil)

Edited: 10 July 2012, 7:50 p.m.