HP-41CX motherboard


A simple one : if i find/buy a Halfnut board from a broken calculator screen, can i put it in a Fullnut case that i have "lost" the board?




Michel! I am trying to contact you!

Please, send me an e-mail! lc_vieira [at] quantica dot com . br

Did you read this post? I completely lost all of the e-mails at IG (lcvig001 at ig dot com punto br).

I have some good news... I was not able to perform such a test before, now I can give your CX mainboard a try.

If you read this post too, chances are we can establish our previous conversations... please?


Luiz (and yes, your CX case will work fine with a CV mainboard... but now I think I can provide your CX mainboard back)


Did you take time to test the board?



Hi, Michel;

I am finishing my 'homework' till this very weekend related to the end of the school semester (final grades and all related paperwork, as you probably know...) then I'll get back to the board.

A few days ago I bought an HP41CV with a single ROM chip. It is a ILG9xxx (cannot see the rest of the code) and I will inspect your CX board to see if there is such kind of ROM chip. Anyway, the idea is to remove the three (or the single) system ROM (0, 1 and 2) then emulate them in the MLDL2000. If the problem persists, I'll remove the other three (X-FCN, Time and CX FCN/TIME) and do what I did with my own CV. If the calculator goes OK in any case, I'll put one ROM at a time back to the board and see which of them causes the problem. If I have a replacement, then I´ll proceed with the change.

My very concerns are related to removing and placing back any MOS chips, mostly when they are so exclusive. All care we have each time it is done is never enough... Grounding ourselves, grounding the devices (soldering iron), discharging electrolytic capacitors, grounding the power lines (BATT+ and BATT-) and using a hairdryer to 'blow' the air around and reduce active ions (works fine, just do not point it to the components too very often) must be performed calmly and sequentially. Takes time, but compensates. These are the main reasons I did not do it so far: everything must be dedicated to that. A CX motherboard demands to be treated like that!


Luiz (Brazil)

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