HP Forum Archive 05

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Strange HP-41 Display Problem Message #1 Posted by Mike on 14 Apr 2001, 11:52 a.m. I have an HP-41CV with a very strange problem. I cannot display A, B, or C in the Alpha register beyond the 6th character. The characters (A,B,C) are saved, they just cannot be displayed beyond the 6th character. All other characters and even shift A,B,C work everywhere. For instance, if I type the following: XXYYZZAABBCCDDEE AABBCC do not show up until the last C pushes A into the first 6 character positions. As I continue to enter characters, eventually, AABBCC show up in the first 6 positions. I thought it was a bad alpha register. But it seems strange that it would only dislike A,B,C and everything else is fine. Wierd! Anyone have a clue what the problem is?

Re: Strange HP-41 Display Problem Message #2 Posted by Steve (Australia) on 14 Apr 2001, 10:18 p.m., in response to message #1 by Mike OK, you didn't get a response last time so, even though I havn't seen a similar problem, I'll see if we can work through some things... Firstly, do you have an XFunctions module? If so, try a program like this: 01*LBL "TD" 02 .255 03 CF 28 04 FIX 0 05*LBL 01 06 CLA 07 1 E3 08 + 09 ARCL X 10 ATOX 11 RDN 12 1 E3 13 - 14 "+______-" (Append 6 spaces then a -) 15 XTOA 16 "+-" (Append a -) 17 AVIEW 18 PSE 19 ISG X 20 GTO 01 21 END This will display all characters in the 2nd last position of the display, with a dash on each side. The ascii code will be shown on the left of the display. Does it only affect A, B, and C? or are other characters affected? I expect at least one other character to show up as a blank :-)

Re: Well I tried it but... Message #3 Posted by Mike on 15 Apr 2001, 3:33 p.m., in response to message #2 by Steve (Australia) The program gave me DATA ERROR so I modified the program to do what you asked and found that the only characters that did not print in 7 and on were. CHRs for 64 (@), 65 (A), 66 (B), 67 (C) So, there was one other that did not print (besides space which was expected). This is truely strange. In every way, the calculator works except that it cannot display these 4 characters after the 6th digit position. Even entering XTOA by typing XEQ ALPHA shows: XEQ XTO The 'A' is not displayed in the alpha register when even entering commands, but it is recorded internally because the instruction works properly.

More than strange. Message #4 Posted by Steve (Australia) on 15 Apr 2001, 7:39 p.m., in response to message #3 by Mike A data error? Where? Mine doesn't. And I hope 32 also showed up as blank :-) That's a VERY weird problem. As a last resort I'd suggest opening up the calculator and looking for bad conections, but frankly, I don't see how bad connections could cause this. The display of the HP41 is (from memory) controlled in 2 halves. Your problem is consistent with this in that only (and exactly) one half is affected. The data in the alpha register is actually held in registers similar to the X, Y, Z, T, L registers, so it looks like they're OK and the problem is indeed a diaplay one. It also affects operations other than the alpha register, since entering commands XEQ "XTOA" are affected, and (I assume) also program listings displayed on the screen, but not the printer (they should print OK).

Re: I'll try printing... Message #5 Posted by Mike on 16 Apr 2001, 9:14 a.m., in response to message #4 by Steve (Australia) > And I hope 32 also showed up as blank :-) That's why I said "(except space which was expected)" > That's a VERY weird problem. > and (I assume) also program listings > displayed on the screen, but not the printer > (they should print OK). I'll try printing. I suspect the problem is related to the connection between the PCB and the keyboard. I had a little problem, not that I think about it, making a good positive connection. Maybe that is where the problem lies. Thanks

Re: Printing works fine Message #6 Posted by Mike on 17 Apr 2001, 11:55 a.m., in response to message #5 by Mike I'm beginning to think this is limited to the ability to display A, B, C only and affects nothing else. I'm going to try a different PCB connector tonight and see if that is the problem. Thanks

Re: Printing works fine Message #7 Posted by Steve (Australia) on 17 Apr 2001, 7:45 p.m., in response to message #6 by Mike I thought it would. When you have the unit open, also look closely at the connections between the main board and the display section. Given that the display is probably like the rest of the HP41 and bitwise serial, AND considering there is no repeating pattern of missing characters, I'd suspect a faulty character generator ROM (If the HP41 actually had one!) Good luck. Anything may work :-)

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