screen contrast 41cx


Is there a way to adjust screen contrast on 41cx? Cannot find any reference in my manuals and ran a search on this forum.




There is no direct or indirect way to change the contrast on a 41CX Fullnut. The 41CX Halfnut (black band around the display) however has additional coding that can be accessed using M-Code to change the screen contrast, but I have never seen any code that actually did this.


Hi Don,

unfortunately it's not possible to adjust contrast on the HP 41C Series.

But in my units it's always pretty good ... perhaps you need new batteries.




there is a way to adjust contrast only in halfnut HP41's, and it is necessary to have at least one ROM module with such feature/function. If I am not wrong, Angel's Toolbox has this feature. There are others I do not know by heart, though.

The main difference between the halfnut and the fullnut may be observed in the shape of the digit segments and in the LCD frame.

This is an image available at the MoHPC:

Hope this helps.

Luiz (Brazil)


Thanks, all. Mine is the original screen and tried the battery change routine and there are still problems. The alpha-numeric output is very readable and dark enough.....the problem is there is some faint images behind the alpha-numeric output. This faint output is on the bottom line (shift, bat, ect) and also on the line above that. It is intermitent, not constant.

I actually have 2 41cx's so I can compare the two and am quite sure it is a calculator display problem and not a problem with my expectations.

many thanks



Sandbox (CTRST, CTRST?, CNT+, CNT-) and Hepax (HEPAX 005) are the only two modules that have functions to adjust the contrast of LCD. On halfnut models only, though.


thanks Miki, I'll just live with the display as is.


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