HP Forum Archive 13

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Halfnut dismantled (with images!) Message #1 Posted by Vieira, Luiz C.(Brazil) on 27 May 2003, 4:17 a.m. Hi, guys; let's see how long will this provider keep my images... Well, here it comes. This is a comparison between halfnut (left) and fullnut (right) PCB, front view. The small black holes in some of the fullnut PCB's holes (nine) indicate the difference between them, concerning to their respective cases. I have successfully used an HP41CV's halfnut PCB in an HP41C's fullnut case. I had to remove the small plastic "posts" where indicated by the black holes. This is a back view of the halfnut's PCB; that's what you see when opening the calculator. The red-and-black wires shown in the top of the image were added to connect external batteries; they do not actually exist in the calculator. Also, both electrolytic and tantalum capacitors were positioned that way so I could scan the image; actual position is shown in the small additional image. This shows the halfnut LCD removed from the mainboard. If you look at previous picture, you'll see there are eight small metal strips around the LCD's hybrid chip (upper, part. # 5061-7255), four in the top (easily visible) and four right below the hybrid itself (not so easily visible, they are like dark mark in four round holes). It's necessary to slightly unfold them in order to remove the LCD. What you see below the LCD is the not-usually visible set of connectors from the hybrid 5061-7255. I decided to go further and removed the LCD driver from the mainboard in order to try to find sny problems, like short-circuited or open trails, cold soldering... but I found no trouble. This HP41CV's halfnut PCB returns .END. REG 63 after SIZE 000, calculator memory cleaned. It should return .END. REG 319. I rebuilt everything back and it is working fine for an HP41C! These images show a sequence where a fullnut LCD is disassembled. The two small "lockers" (black flat fasteners) are made of plastic, and are easily removed. I must warn that it's necessary having careful hand and fingers movements; if you force too much, you may bend the metal bridges or even break their soldering tabs, permanently damaging the LCD assy. After inspecting aligned pads for both LCD's I got to the conclusion that fullnuts' and halfnuts' LCD's are not interchangeable; I mean the LCD itself, the glass parts, not the drivers. (sorry, Gordon) As I'm having more information, I'm posting. I hope these images help others. Feedback is always welcome. Thanks and enjoy. Luiz C. Vieira - Brazil

Re: Halfnut dismantled (with images!) Message #2 Posted by Meindert Kuipers on 27 May 2003, 7:20 a.m., in response to message #1 by Vieira, Luiz C.(Brazil) Impressive piece of disassembly! Just a question, I have an HP41CX. What is in the PCB that sits above the CPU (at least I think it is the CPU). Are all the extra ROMs in there (time, xfun)? Meindert

Re: Halfnut dismantled (with images!) Message #3 Posted by Vieira, Luiz C. (Brazil) on 27 May 2003, 8:38 a.m., in response to message #2 by Meindert Kuipers Hi, Meindert; thaks for your supporting words. I have both halfnut and fullnut 41CX and as far as I know (and read about), the extra halfnut-exclusive assembly contains TIME and X-Fucntions hardware only. The hybrid RAM/ROM & display driver is not the same for the CX too (ID #: 5061-7261), because CX ROM contents are different, as you know. Unfortunately this is all I know. In time: congrats for your amazing MLDL development. Best regards. Luiz C. Vieira - Brazil

Re: Halfnut dismantled (with images!) Message #4 Posted by Meindert Kuipers on 27 May 2003, 3:37 p.m., in response to message #3 by Vieira, Luiz C. (Brazil) I am asking this because my MLDL may be small enough to replace the bridge board (it would be bigger, but could fit inside). The only thing it could not (yet) emulate is the time module. Meindert

Re: Halfnut dismantled (with images!) Message #5 Posted by David Smith on 27 May 2003, 2:27 p.m., in response to message #2 by Meindert Kuipers The bridge CPU board in the 41CX halfnuts is the clock circuitry. I think it also contains the clock ROM functions so that if you transfer it onto a 41CV, you get the equivalent of the 41C Time Module, but I have never done this.

X-Functions in the HP41CX? Message #6 Posted by Vieira, Luiz C. (Brazil) on 27 May 2003, 3:08 p.m., in response to message #5 by David Smith Hi, David; again, to keep me up-to-date about the internals and not to spread bad information around, where are the X-Functions stored in the HP41CX? I remember I read once, I'm not sure if it was here, that the HP41CX halfnut had the extra ROM's for both Time and X-Functions in the bridge board, and that the CX-only functions for time and X-Fcn were recorded with basic CX-ROM, in the hybrid chip. Is it an incorrect information? If so, I must update my own database. I also found that the CX fullnut has some extra ROM chips, and I remember I saw an extra X-tal. I did not search for any specific clock chip, but I know it must exist. Thank you again for calling my attetion to these facts. luiz C. Vieira - Brazil

Re: X-Functions in the HP41CX? Message #7 Posted by Tony Duell (UK) on 27 May 2003, 5:12 p.m., in response to message #6 by Vieira, Luiz C. (Brazil) In the fullnut, the timer chip is the 20 pin (I think) IC at the right of the PCB (looking at the component side). That's just the timer, the programs to drive it are in one of the ROM chips). In the halfnut, I beleive. the 'bridge board' hybrid contains the timer chip, the extended memory RAM, and 12K of ROM (page 3 and both page 5s) containing the extended functions, timer functions, and CX specific functions. However, the main 12K ROM (pages 0, 1, 2) in the display driver hybrid is different between CV and CX machines -- adding the bridge board to a CV will add the timer functions (and the time chip), but it will not recognise the extended functions.

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