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HP Forum Archive 14

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HP-41 Brain Transplant
Message #1 Posted by Paul Goertz on 8 May 2004, 11:30 a.m.

I have acquired 2 HP-41's over the recent months. The first is a 41C, in excellent cosmetic condition, but non-functioning.

The second is a 41CX that functions well, but has damage to the keyboard; the most pronounced problem is that the ENTER key looks as though it got heated to the point that one end twisted and sagged.

My question is: is it possible (& relatively painless) to perform a "brain transplant" from the 41CX to the 41C? That is, retain the 41C's case, keyboard & LCD, but replace the circuit board(s) with those from the 41CX?

I know that there are a couple of places that will repair these, but I want to try my hand first (not to mention save a few $).

Thanks, Paul

      
Re: HP-41 Brain Transplant
Message #2 Posted by Randy Sloyer on 8 May 2004, 1:43 p.m.,
in response to message #1 by Paul Goertz

The answer is probably yes, if:

  1. Both units are fullnuts.
  2. The C is not an early steep key version - the LCD's are incompatible with later models.

If the C has pink polymer zebras (early models had them), toss them and use the gold wire connector(s) from the CX. You may need to pry the spacer off the CX lower posts to use them, depends on the version.

            
Re: HP-41 Brain Transplant
Message #3 Posted by Paul Goertz on 10 May 2004, 5:56 p.m.,
in response to message #2 by Randy Sloyer

Bummer . . . the C has "steep keys", and the CX is a half-nut. At least I'll know what to ask for if I buy another machine for parts.

Many thanks,

Paul

                  
Re: HP-41 Brain Transplant
Message #4 Posted by Randy Sloyer on 10 May 2004, 6:07 p.m.,
in response to message #3 by Paul Goertz

I've got a half-nut CX here with a broken lcd, the keyboard/logic board is otherwise a-okay. I could build you a frankin-calc with this one and your trashed keyboard unit. Email me if you want to try. etron at comcast dot net

      
Re: HP-41 Brain Transplant
Message #5 Posted by Tony Duell on 8 May 2004, 4:04 p.m.,
in response to message #1 by Paul Goertz

You need to check if they're 'fullnut' or 'halfnut' machines. The easy way to tell is that the halfnuts have a black border to the display, under the window. If it's one of each, forget it. They're very different inside. IfThey;re both halfnuts, it's non-trivial to do this. You have to dismantle the heat-staked keyboard, and this is not easy to get back together so that it stays together and feels right. If they;'re both fullnuts then most likely the logic boards will just swap over. Keey any washers, etc with the case they go with. Some very early C's have a different display driver, which needs a different capacitor on the logic board. I can check exactly what needs to be done if you have problems after putting the CX board into the C case. Remember these machines use CMOS circuitry and can be damaged by static discharge.

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