HP41 CL Board installation

[Benoit Maag]

I got my V5 board last week

The 41C I wanted to install it into was an older machine (S/N 2036A01297), which has 2 metal nuts holding down the motherboard onto the display/keyboard PCB (see picture). The metal nuts screw directly onto the plastic screw posts - needless to say the thread on the plastic posts is easily damaged.

That is what happened to me. When I screwed the nuts back to hold the 41CL board, they did not press it enough to make contact with the display/keyboard PCB, and I could not get the 41CL to work.

Luckily, I live a few miles from Monte, and he identified the problem. The solution was to use the calculator back of a newer HP-41CV (S/N 2201S41038) which I had. For such newer models, there are no nuts to hold the motherboard - the calculator back has some plastic cups that press the motherboard down

In conclusion: if you have an older HP-41C with the metal nuts, be very careful when you remove the nuts and screw them back. For the later models without the nuts, the installation is quite straightforward

I will need to re-assemble my leftover 41C-41CV hybrid. My objective is to create the little cuts that press the motherboard down - probably glueing a few nylon washers together and onto the calculator back. Will post procedure once (if) validated

Gene pointed out at the last HHC that installing a 41CL board may be scary, but it is actually very straightforward. And the result is an unbelievable machine...