HP Forum Archive 16

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HP 15C keyboard Message #1 Posted by Thor Lansen on 28 Jan 2007, 4:30 p.m. I have an HP 15C in which all keys work but I upon close examination I noticed three keys ("+" "-" and "x") are resting a bit lower (about 0.5 mm) than the others. They have a "click" (maybe a bit less than the others) and after reading an early post about broken contact strips I was wondering if it is something of concern (i.e. are keys with that condition prone to early failure?) and if so if it needs/can be repaired. Thanks, Thor.

Re: HP 15C keyboard Message #2 Posted by Gerson W. Barbosa on 28 Jan 2007, 5:41 p.m., in response to message #1 by Thor Lansen I have an HP-15C that had exactly this problem in the same region of the keyboard: keys '+', '-' and 'Sigma+'. The keys had a weaker and annoying click sound and the keys appeared to be sticky, like some kind of gluey stuff was preventing them to get back to their normal position. I opened it up and found no dirt inside (I had to cut the plastic rived out to gain access to the domes). As it was open, I cleased the region with a dry cloth and a soft brush. After reassembling the calculator, the keys got back to the normal height. I don't advise you to open it though. I only did that because I also wanted to speed it up. I think there is a way to fix this without opening the calculator. Let's wait for other suggestions. As that was the first time I had opened up an 15C, the rivets don't look so good now but the keyboard is steady as before: http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv016.cgi?read=99306 Regards, Gerson.

Re: HP 15C keyboard Message #3 Posted by Thor Lansen on 29 Jan 2007, 7:37 p.m., in response to message #2 by Gerson W. Barbosa Thank you Gerson for the information. I am going to wait for now unless somebody comes up with a way of doing the work without opening the calculator (or at least without having to cut the plastic rivets). If things get worse I will take a look "under the hood and get my hands dirty" (I might also try to speed it up). Regards, Thor.

Re: HP 15C keyboard Message #4 Posted by Gerson W. Barbosa on 29 Jan 2007, 9:26 p.m., in response to message #3 by Thor Lansen You're welcome! I think you should not open up the calculator just because of this. The keys may be lower but most likely there's nothing wrong with them other than that. Anyway, in the event you have to cut the rivets one day, cut around the edges, six or seven straight cuts with a sharp knife (I used a Victor Inox Swiss knife), so that they remain tall enough to allow being melted again. And please do not do a slovenly job like I did :-) Regards, Gerson.

Re: HP 15C keyboard Message #5 Posted by Thor Lansen on 1 Feb 2007, 1:09 a.m., in response to message #4 by Gerson W. Barbosa Gerson, thanks for the tip. The instructions I have read said to cut the rivets flat but by doing it the way you suggested you leave material to solder them back. I wonder if one could use a tool similar to a hole puncher of the diameter of the pins to do the cut? That way you might be able to make a cleaner cut and leave more material than cutting around with a sharp tool. I am not going to touch the calculator now but it might be something to consider. Thanks again. Regards, Thor.

Re: HP 15C keyboard Message #6 Posted by Randy on 30 Jan 2007, 9:04 a.m., in response to message #3 by Thor Lansen IMO, there is nothing wrong with the unit, let it be. In a Voyager, there is a rubber sheet between the keys and the key domes. It keeps the keys from rattling and dampens the snap when the dome flexes. On keys that are heavily used, over time, the key pin punctures the rubber sheet allowing the key to sit a bit lower than the other keys.

Re: HP 15C keyboard Message #7 Posted by Les Wright on 30 Jan 2007, 11:34 a.m., in response to message #6 by Randy I have a similar issue involving the COS and x<>y keys of my 11C. There is also a significant scratch over the word CLEAR, so I am wondering if a previous owner dropped something on the keyboard. But it works, and this is a daily use calculator, not a collectible, so I am not going to monkey with it. Les

Re: HP 15C keyboard Message #8 Posted by Thor Lansen on 1 Feb 2007, 12:32 a.m., in response to message #7 by Les Wright Les, I am glad this did not happen to my favorite calculator, the HP42S. It used to be my 41CX (that I used through college) but thanks to you I decided to try the Thomas Okken Free42 emulator and I got hooked, and I had to get the real thing. I was lucky to get a very nice HP42S at "TeS". So even thought you cost me 350 bucks I thank you. Regards, Thor

Re: HP 15C keyboard Message #9 Posted by Les Wright on 1 Feb 2007, 2:00 a.m., in response to message #8 by Thor Lansen I still use Free42 more than the real thing. The main weakness of the 42S (and indeed the saintly 15C) is that it has all of that program memory and fingers are the only way to get programs into it. Recently, I have been turning quite a few listings from this site's software library into barcode and RAW files using hp41uc. The barcode gets the programs into my 41CV and onto cards. The RAW files I can use directly, usually with no modification, in Free42 on my Palm. In that setting the programs are impressive to use. I am pretty interested in JM Baillard's numerous higher level math routines (error function, complete and incomplete gamma functions, beta functions, Fresnel integrals, etc.) Most of these routines (which are, incidently, examples of compact and efficient programming) take a few seconds on the real calculators to return results if iteration over, say, terms of a series or continued fraction are needed. Yet on the Free42 they return results almost instantaneously, or at worse will take a second or two if "tough" arguments are presented (e.g., computing the incomplete gamma function Gamma(a,x) by continued fraction when x is much less than a). More over, the displayed results are typically correct to all twelve digits, since the internal 25 digit accuracy gives more guard digits than you could possibly want. I have even ported the PPC ROM Romberg integration routine IG for use on Free42 in preference to the built-in integrator. I think it is a little faster, and one can choose to display or "print" interim results--plus the code isn't a black box to me and I know what it is doing in its compact 90 steps. The 42S was my first ebay calculator purpose. I spent $300 (plus taxes and shipping, which added another $70 I think) for what is basically a working but dented field quality calculator. It works, and it came with manual and box. Since then I have seen 42's in better shape for half the price, but I try to live without regret. I have spent a little too much for some things, but have been compensated by some great finds, like an excellent HP80 from our friend Namir for only $80. There is some karma here. Les

Re: HP 15C keyboard Message #10 Posted by Thor Lansen on 1 Feb 2007, 12:20 a.m., in response to message #6 by Randy Thank you Randy, I am going to follow your advise and let it be. Regards, Thor.

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