HP Forum Archive 10

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HP-41C/CV/CX display contrast Message #1 Posted by Don Davis on 15 Jan 2003, 9:13 a.m. I have an older 41C (also a 41CX) on which the LCD display is a little faded compared to some others. Is it possible to open these up and boost the contrast a bit - may a resistor change or something? thanks, Don

Re: HP-41C/CV/CX display contrast Message #2 Posted by Dave on 15 Jan 2003, 9:22 a.m., in response to message #1 by Don Davis Newer half nut HP-41 calcs display is not as good as original designs. do not know how to change this though.

Re: HP-41C/CV/CX display contrast Message #3 Posted by Vieira, Luiz C. (Brazil) on 15 Jan 2003, 11:57 a.m., in response to message #1 by Don Davis Hi; I have an HP41C, earlier fullnut, that has a faded display, too; also, it fades a bit more when one of the four toggle keys is used (almost vanishes some segments). I tried to use foam to keep it without movements and even resoldered the contacts, but I got no positive results. About the newer hafnuts, their LCD allows contrast control/adjust, but with the use of specific internal commands and registers, available in some extra modules (if I am not wrong, CCD ROM and HEPAX allow it, I am not sure about PPCC ROM). Also, the halfnuts LCD's allow all lower-case characters to be shonw, instead of the known basic "a" to "e" in the earlier fullnuts. Cheers.

Re: HP-41C/CV/CX display contrast Message #4 Posted by Don Davis on 15 Jan 2003, 2:56 p.m., in response to message #3 by Vieira, Luiz C. (Brazil) This is very interesting about the internal commands to adjust contrast of halfnut models. I do not have Hepax nor CCD. Is there any way to manipulate the required registers otherwise? Don

Re: HP-41C/CV/CX display contrast Message #5 Posted by Vieira, Luiz C. (Brazil) on 15 Jan 2003, 4:47 p.m., in response to message #4 by Don Davis Hi; Unfortunately I do not have any of these dream little boxes, I only have and know the X-Functions and the standart perypheral devices (82143A, 82153 and 82104) plus the HPIL module. If I have any of these modules, I would for sure dig them to hell, so I could find a way to answer you. About synthetic coding, I'm not sure there is any specific code to access these guys. And remember that only the halfnut models allow this sort of control. I have the map with lower case letters and the internal registes used to control them. This map was sent by one of the contributors in here. I surely know who is he, and I'm a lot thanked, but I do not mention names prior to ask for their authorization, O.K.?. If I know something more about it, I'll post later. Best regards and success.

Re: HP-41C/CV/CX display contrast Message #6 Posted by Don Davis on 15 Jan 2003, 5:01 p.m., in response to message #5 by Vieira, Luiz C. (Brazil) Thanks very much! I do have the extended functions module, so if there is a way to control with that, I could use it. best regards, Don

Re: HP-41C/CV/CX display contrast Message #7 Posted by David Smith on 15 Jan 2003, 5:59 p.m., in response to message #1 by Don Davis The fullnut display was optimized for viewing straight on. The halfnut was optimized for viewing at an angle like when the machine was sitting on a desk or held striaght out in the hand parallel to the ground. Fullnuts have a wider viewing angle than the halfnuts. Low contrast displays can be caused by a faulty temperature compensation circuit. Unfortunately halfnut displays are not serviceable. See the HP41 service manual on the HPMUSEUM CDROM set for fullnut info.

Re: HP-41C/CV/CX display contrast Message #8 Posted by Juan J on 16 Jan 2003, 12:21 a.m., in response to message #7 by David Smith Earlier fullnut 41s' displays had no means of adjusting the contrast. Halfnut 41s not only had adjustable display contrast, but also an extended character set, which can be accessed using M-code. The HEPAX module uses a bug in the 41's operating system to squeeze some extended multi-functions, as the manual calls them, that are executed with the HEPAX nnn function. Incidentally, [XEQ] HEPAX 005 regulates display contrast on halfnuts using a number in the X register (the number must be entered befores executing the function.) The default is, if I remember correctly, 5, and the contrast can be changed from 1 to 14. Now there's something I've been wondering about lately. WOuld it be possible to plug an HEPAX into a halfnut, set the contrast, and then unplug it? If applicable, could be a way to adjust the contrast on newer (halfnut) 41s. I only have a fullnut 41C and a halfnut 41CX and cannot try this. Perhaps anyone outthere with an HEPAX and two halfnuts?

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