HP Forum Archive 11

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Who wants a 41CV for $120? Message #1 Posted by Jeremy on 23 Mar 2003, 10:21 p.m. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3014972757&category=11713 I think that is a pretty good price, no? -Jeremy

Re: Who wants a 41CV for $120? Message #2 Posted by Karl Schneider on 24 Mar 2003, 2:55 a.m., in response to message #1 by Jeremy Not a *bad* price, but this CV is an older Fullnut version with no manuals or case, and the only extra is the Math module, which can be had on eBay with the necessary manuals for around $10. CV's don't command the price of CX's, which have the built-in functionality of the Extended Functions and Time modules, plus a few other features, like better directory listings. No great bargain...

Re: Who wants a 41CV for $120? Message #3 Posted by John K. (US) on 24 Mar 2003, 5:28 a.m., in response to message #1 by Jeremy If you really want this one, then $120 isn't bad. Of course, you could go ahead and bid normally and take your chances. I've gotten a few good deals that way.

Have you seen this? Message #4 Posted by Vieira, Luiz C. (Brazil) on 24 Mar 2003, 6:58 a.m., in response to message #1 by Jeremy Hello, Jeremy; I looked at the pictures and this one called my attention: For what I see, someone tried to open it without any concerns about screws and the like. I'd take care with it. My thoughts and concerns. Luiz C. Vieira - Brazil

Re: Who wants a 41CV for $120? Message #5 Posted by Diego Diaz on 24 Mar 2003, 4:44 p.m., in response to message #1 by Jeremy Well... at least there is somebody out there that thinks it's not an unreasonable price: It's been sold in 15 hours!! Anyway it seems really overprized to me... :-0 Cheers!!

Re: Who wants a 41CV for $120? Message #6 Posted by Paul Brogger on 24 Mar 2003, 6:19 p.m., in response to message #5 by Diego Diaz I probably should have bid rather than jumped -- but I've been wanting one. Besides, the seller has offered a money-back guarantee. But I assume I'll keep it. (If it's truly overpriced, then I'll be a little red-faced for a while . . . )

Re: Who wants a 41CV for $120? Message #7 Posted by Randy Sloyer on 24 Mar 2003, 9:17 p.m., in response to message #6 by Paul Brogger Paul, First, forgive me if this has been mentioned before. I saw the side of the case looked like somebody tried to pry it open with a screwdriver. In the past when confronted with this injury, I've just trimmed the damage with an x-acto knife, leaving a scar, but I recently stumbled upon a better way. I found that I could rub or burnish the plastic back into place with a wooden "popsicle" stick. It works well on the textured Pioneer cases. I think it might be a bit more obvious on the smoother 41 case, but it might be worth a try.

Re: Fixing the calculator's case edge Message #8 Posted by Paul Brogger on 24 Mar 2003, 10:53 p.m., in response to message #7 by Randy Sloyer Why, thanks for the suggestion. I'd already guessed that cutting would smooth it, and that burnishing might be possible. The popsicle stick will definitely work better than whatever (probably metal) instrument I might have tried. And, I've got a 42s (due to be keyboard-repaired, memory-upgraded, and sold) with some similar marks on it -- I'll try it on that one too.

I've got a better one: Message #9 Posted by on 25 Mar 2003, 2:21 p.m., in response to message #1 by Jeremy http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3015260351&category=3294 The contrary is that one: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3010907901&category=11713

Re: I've got a better one: Message #10 Posted by Paul Brogger on 25 Mar 2003, 5:32 p.m., in response to message #9 by Yes, it appears that you do . . . I guess I could have done worse, and could have done better. I'll take a bit more time, next time.

Re: I thought I did -- now, can it be fixed? Message #11 Posted by Paul Brogger on 30 Mar 2003, 12:46 p.m., in response to message #1 by Jeremy I offer my naiive experience in the interest of educating the greater community. (And, I'm asking for advice . . . ) I just received the HP-41CV. I suppose it is essentially as advertised. Upon disassembly, there is some battery leakage/corrosion noted, and the case is indeed scarred from a brutally amateurish disassembly attempt. The real problem is that in the process of prying the thing apart, the curious person with the screwdriver broke out the back-case seats of the two screws under the upper rubber pads (and almost did the same for the lower two screws). So, the case was rattling about and was generally not well held-together. (The broken plastic seats were dangling on the screw heads like horribly misshapen washers . . . ) I've temporarily got flat metal washers under the screw heads to hold things tight -- I'm now going to buy the "N" cells to test the unit's operation. If I'm to keep this thing, I want to either find some kind of flat-head screw which will allow me to put on the rubber feet, or to epoxy back the plastic seats for the original screws. Looking at the pieces, however, it appears that the seats will simply be pulled away from the back case again, even if epoxied, when things are tightened down. That, and the requirement that the epoxy job will have to fit the limited space in the power/expansion connection block (or whatever it's called) that is held in place by those two screws, has got me doubting whether the repair can be done. So, does anyone have any experience with this kind of repair? (I'll start looking through the "Repairs" articles and searching the Archives soon, but don't have time right now . . . ) Thanks.

Re: I thought I did -- now, can it be fixed? Message #12 Posted by David Smith on 30 Mar 2003, 4:04 p.m., in response to message #11 by Paul Brogger Don't use epoxy... use a plastic welding solvent sold at most hobby shops. The stuff I use is called Tenax... it is just methylene chloride (or dicholoromethane). It melts the plastic and lest you weld it back together. I brush it on both sides (rather liberally) and clamp the joint for at least 24 hours. Work fast... it evaporates very quickly. Also be careful not to squash the softened plastic with the clamps.

Re: Yes, this glue fixes some plastics VERY well! Message #13 Posted by Paul Brogger on 8 Apr 2003, 9:27 a.m., in response to message #12 by David Smith For those who may be shopping, I found a brand of methylene choride (or, I guess, dichloromethane) glue at the local hobby shop -- the brand is "Ambroid PROWELD". It did wonders on both my HP-41C back case (screw seats) and a Topcat battery door (broken in half in the mail). And I second all the usage advice offered in the post above! The stuff does evaporate almost instantly. For the battery door, I arranged the pieces so that they were held in approximation with rubber bands (and held the rubber bands off the surface of the joint with toothpicks), cracked open the break just a little bit, filled it in with ProWeld, and then let it settle back into alignment. It seems to have worked perfectly. Thanks for the info!

Re: Yes, this glue fixes some plastics VERY well! Message #14 Posted by Tony Duell (UK) on 8 Apr 2003, 6:35 p.m., in response to message #13 by Paul Brogger In the UK, dichloromethane is available from _good_ model shops under the brand name 'Plastic Weld'. It comes in a little brown glass bottle. You're right. This stuff is excellent for plastic repairs. As I mentioned in a previous message, if you have space on the back of the repair (say you've got a case part that's snapped in half, or a shattered keyboard bezel from a 98x0), stick it together as usual, then cut out a piece of thin cloth to fit over the back, put it in place, and brush it with the solvent. Then force it into the softened plastic. It won't look pretty (but it's on the back, right), but it will make the repair even stronger.

Re: Yes, this glue fixes some plastics VERY well! Message #15 Posted by Speck on 8 Apr 2003, 11:41 p.m., in response to message #14 by Tony Duell (UK) Heh-heh-heh! It's Composites class all over again!

What about this solvent cement? Message #16 Posted by Ellis Easley on 9 Apr 2003, 4:57 a.m., in response to message #15 by Speck Paul, does the Ambroid Proweld list the ingredients? Is it 100% methylene chloride? I found their website (http://www.ambroid.com/Ambroid.html) but it doesn't have Material Safety Data Sheets available - the MSDS will list the ingredients if they aren't proprietary. The Ambroid website does give this description of Proweld: "Its unique "low surface tension" formula assures speedy absorption into the joint ..." I found a brand called "Weld-On #4" by IPS Corporation (http://www.ipscorp.com/ind_html/acrylics.html), for joining acrylic, which contains (from the MSDS) 50% methylene chloride, 50% trichloroethylene and "<1%" methyl methacrylate monomer. I'm wondering if the ingredients other than methylene chloride will affect the performance with a calculator case. I bought it at a plastic distributor where I went to get a sheet of plastic to repair a window. The IPS Corporation also makes "Weld-On #3" and "#5". #3 is the same three chemicals in the proportions 90% - 9% - "<1%". #5 is 65% methylene chloride, 25% methyl methacrylate monomer and 5-10% glacial acetic acid. The product bulletin for #4 says: "WELD-ON 4 is formulated as a blush-resistant cement for bonding acrylic plastic to itself. It will also form strong bonds with other plastics such as styrene, butyrate and polycarbonate to themselves. It will not bond to certain cross-linked acrylic." Further on it says: "Some plastic fabricators prefer WELD-ON 4 to WELD-ON 3 because it is less likely to leave white marks (commonly called blushing). However, if you need faster cement than this one, we suggest you try Weld-On 3 or for slower set, try Weld-On 5." Apparently the higher proportion of trichloroethylene in #4 slows the drying (and prevents white spots) and the acetic acid in #5 slows it even more (that or the ??? monomer).

Re: Ambroid PROWELD Label Message #17 Posted by Paul Brogger on 9 Apr 2003, 9:44 a.m., in response to message #16 by Ellis Easley For ingredients, it says only "Contains methylene chloride." and "... contains a chemical known to the State of California to cause cancer." On the front it says "Professional Plastic Welder for Styrene, Butyrate, ABS & Acrylic (Lucite or Plexiglas)" That's it for ingredients & applications -- the rest is hype, cautions, and directions. We're about to buy our digital camera -- If this is still an issue, I'll take a picture or two, for what that may be worth . . .

Re: Ambroid PROWELD Label Message #18 Posted by Ellis Easley on 9 Apr 2003, 6:01 p.m., in response to message #17 by Paul Brogger No, that's enough information. The product bulletin for the stuff I have says: "Methylene Chloride and Trichloroethylene are listed as cancer causing materials." I think trichloroethylene is the same as carbon tetrachloride which used to be a very common spot remover (Carbona) and which was removed from common use many years ago. I think it was even used in fire extinguishers! They were built like giant syringes. I think what I have will just dry more slowly than a higher concentration of methylene chloride. Interesting that the feature listed first is the non-blushing aspect, this might be a plus for the sake of cosmetics. I'm going to try the solvent on some less important repairs that I have saved up before I use it on my HP67. It's been through enough!

Re: I thought I did -- now, can it be fixed? Message #19 Posted by Ellis Easley on 30 Mar 2003, 4:35 p.m., in response to message #11 by Paul Brogger Look in the Archives for David Smith's advice on using a solvent (methylene chloride AKA dichloromethane) to glue broken posts back together. Also how to replace them if they can't be fixed. I haven't used this solvent yet but I have it on my shopping list. Also, I use what I call a "burnishing tool" to smooth gouged plastic. I have a complete description below, but first ... I had a similar Ebay experience with an HP67 with damage the seller hadn't mentioned (new seller, was courteous and refunded part of my money.) The unit appeared to be unused - no leakage, no wear on the springs that guide the card, the wheel was gummy but clear and stuck to the nylon (delrin?) roller at just one point. I actually removed the old wheel from the hub in one piece! That was the good news. The bad news was somebody tried to pry it open with a screwdriver from the front edge. They had found and removed the screws under the front rubber feet but couldn't find the others (I blame HP in part for hiding them. I suppose they used the label to cover a couple of screws so they could tell definitively whether a unit under warantee had been opened, but I think that kind of behavior is sort of like leasing, rather than selling, equipment to your customers.) Luckily the electrical damage was limited to slight bending of a couple of the gold hairpin-like contacts that join the PCB's. Most of the damage was displaced plastic around the gap that joins the top and bottom. Then I guess out of frustration from failing to open the unit, the "perp" stuck a narrow screwdriver in one of the screw holes and twisted, breaking the post and deforming the hole. I don't mean any insensitivity to anyone, but this unit was raped. I repaired most of the outside plastic damage with the burnishing tool I mentioned before and will now describe: Regarding smoothing gouged plastic with a popsicle stick, I use a tool I inherited from my father which I call a burnishing tool (although I don't remember what he called it). It is like a short (1.65" long) stout (0.36" X 0.24" maximum cross section) dagger with blunt knife edges and point (though I think you could penetrate a skull with it!) and curved sides, with a wooden handle. The finish is very smooth but not a mirror finish. With it I can often push the extruded plastic back into the void by using many small strokes and trying to do just a little each stroke. It can leave a pretty smooth finish depending on the type of plastic (though I don't know different types of plastic apart - that is something I would like to learn more about.) When I want to get a smoother finish, I use a tiny bit of toothpaste and rub with my finger, adding a bit of water when it dries out. It seems possible to generate a considerable amount of friction this way, judging by how hot it gets - you can actually go too far (causing worse scoring than when you started) with just toothpaste and finger! I found a similar tool in the Small Parts catalog, they call it a burnisher and it is like mine except curved. It is in their catalog 22, which appears to be the same one available for download today (www.smallparts.com). I guess you have to download the entire 35MB file! but I think it is worth it, it's a real wishbook of tools and materials. The tool I found is on page 393 and the catalog number is HM-296. It is near deburring tools and files. There was no entry for "burnish..." in the index.

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