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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
Unit with charger & owners handbook. Working.
Best offer. Peter |
#2
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On 8/7/18 8:24 PM, Peter Jason wrote:
Unit with charger & owners handbook. Working. Best offer. Peter https://en.wikipedia.org/wiki/HP-25 -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
#3
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On Tue, 7 Aug 2018 20:30:56 -0500, Fox's
Mercantile wrote: On 8/7/18 8:24 PM, Peter Jason wrote: Unit with charger & owners handbook. Working. Best offer. Peter https://en.wikipedia.org/wiki/HP-25 Thanks. Here's a picture of mine. https://postimg.cc/image/466owlrsn/ |
#4
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On Wed, 08 Aug 2018 11:24:28 +1000, Peter Jason wrote:
Unit with charger & owners handbook. Working. Best offer. Peter Is it an HP25 or HP25c? Your photo looks like HP25. http://www.hpmuseum.org http://www.hpmuseum.org/hp25.htm Very old prices http://www.hpmuseum.org/collect.htm#diff eBay completed auctions for HP25 https://www.ebay.com/sch/i.html?_from=R40&_nkw=hp+25+calculator&_sacat=0&LH _TitleDesc=0&rt=nc&LH_Sold=1&LH_Complete=1 Looks like the running price for a complete calculator (charger, book, box, etc) is $50 to $100. However, 3 have sold for $150 to $225. I suggest you try selling it on eBay or Craigslist. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#5
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On Wed, 8 Aug 2018, Peter Jason wrote:
Unit with charger & owners handbook. Working. Best offer. Peter This is for the repair of electronic equipment. It's not a buy and sell newsgroup. Michael |
#6
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On 9/08/2018 12:37 AM, Michael Black wrote:
On Wed, 8 Aug 2018, Peter Jason wrote: Unit with charger & owners handbook. Working. Best offer. Peter This is for the repair of electronic equipment.Â* It's not a buy and sell newsgroup. Â* Michael At least it's not political :-) |
#7
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On Thu, 9 Aug 2018 17:20:15 +0800, Rheilly Phoull
wrote: On 9/08/2018 12:37 AM, Michael Black wrote: On Wed, 8 Aug 2018, Peter Jason wrote: Unit with charger & owners handbook. Working. Best offer. Peter This is for the repair of electronic equipment.* It's not a buy and sell newsgroup. * Michael At least it's not political :-) I've noticed that any new topic that appears, degenerates into a political discussion within about 5 messages. It doesn't seem to matter what the topic might be or who is doing the posting. The political discussion continues until someone mentions Trump, where it degenerates into one-line comments of little intelligence and less importance. At least it's not an AGW discussion, which tend to be endless and have been beaten to death long ago. Welcome to the new Usenet. Incidentally, I collect old LED HP calculators. You won't see quality design, materials, and construction like that ever again. After a rough day of dealing with unrepairable Chinese junk, I rather enjoy fondling gold plated PC boards, dual shot injected keys that don't rub off, documentation written in readable English, mostly bug free firmware, batteries that aren't intentionally overcharged, and wall warts that don't blow up. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#8
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On Thursday, August 9, 2018 at 10:53:23 AM UTC-4, Jeff Liebermann wrote:
The political discussion continues until someone mentions Trump, where it degenerates into one-line comments of little intelligence and less importance. Yeah, those Trump Bashers are nothing if not persistent. Incidentally, I collect old LED HP calculators. You won't see quality design, materials, and construction like that ever again. After a rough day of dealing with unrepairable Chinese junk, I rather enjoy fondling gold plated PC boards, dual shot injected keys that don't rub off, documentation written in readable English, mostly bug free firmware, batteries that aren't intentionally overcharged, and wall warts that don't blow up. I have a question for you Jeff concerning the HP line. I have an HP34C that I bought new back around 1980 or so to replace my stolen TI SR-51A. It had always been a little flakey but a quick thump brought it back around. A few years later I decided to have a look inside when it required more physical persuasion to behave. I took a picture of the front keys in case they decided to jump out and get mixed up (they did), but I was surprised to find the half dozen ICs *not* soldered down to the flexible circuit board. They maintain connection by the foam cushion beneath the flex circuit that maintains pressure between the flex circuit and the ICs. I removed each IC, cleaned all the pins and the flex circuit lands, put a tiny bit of dielectric grease on each IC pin, and reassembled. It behaved itself for quite some time. Right now it's been in storage for many years but every once in a while I wonder if the correct solution would be to tack solder them down. I'm sure the foam pad looses a bit of rebound over the years. What do you do when you run across flakey IC contacts in an HP? |
#9
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On Thursday, August 9, 2018 at 3:34:57 PM UTC-4, John-Del wrote:
I'm sure the foam pad *looses a bit of rebound over the years. *Loses... |
#10
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On Thursday, August 9, 2018 at 4:06:30 PM UTC-4, John-Del wrote:
On Thursday, August 9, 2018 at 3:34:57 PM UTC-4, John-Del wrote: I'm sure the foam pad *looses a bit of rebound over the years. *Loses... Oh, I dunno - there is a certain elegance to "loosing" a rebound. Peter Wieck Melrose Park, PA |
#11
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On Thursday, August 9, 2018 at 4:09:37 PM UTC-4, wrote:
On Thursday, August 9, 2018 at 4:06:30 PM UTC-4, John-Del wrote: On Thursday, August 9, 2018 at 3:34:57 PM UTC-4, John-Del wrote: I'm sure the foam pad *looses a bit of rebound over the years. *Loses... Oh, I dunno - there is a certain elegance to "loosing" a rebound. Peter Wieck Melrose Park, PA LOL. It was *you* Peter that I had in mind when I made that correction!!! I figured if anyone would catch that goof and make me pay for it it would be you. |
#12
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On Thu, 9 Aug 2018 12:34:54 -0700 (PDT), John-Del
wrote: I have an HP34C that I bought new back around 1980 or so to replace my stolen TI SR-51A. It had always been a little flakey but a quick thump brought it back around. A few years later I decided to have a look inside when it required more physical persuasion to behave. I took a picture of the front keys in case they decided to jump out and get mixed up (they did), but I was surprised to find the half dozen ICs *not* soldered down to the flexible circuit board. Yep. It relies on the pressure provided by a foam pad to make the connection. Bad bad bad idea: http://www.hpmuseum.org/hp34.htm They maintain connection by the foam cushion beneath the flex circuit that maintains pressure between the flex circuit and the ICs. I removed each IC, cleaned all the pins and the flex circuit lands, put a tiny bit of dielectric grease on each IC pin, and reassembled. It behaved itself for quite some time. Right now it's been in storage for many years but every once in a while I wonder if the correct solution would be to tack solder them down. I'm sure the foam pad looses a bit of rebound over the years. What do you do when you run across flakey IC contacts in an HP? If the foam pad was in good shape (springy), I would add a 2nd foam pad to give it more pressure. This added pad is rather thin. I should repalce both, but can't find a suitable sheet of foam. I now have access to a laser cutter, so I might be able to cut some foam that will work. I think ordinary soldering is a bad idea and have never tried it. However, if you do decide to try it, I suggest you use low temperature 180C bismuth solder paste, liquid flux, and a temperature controlled toaster oven. https://www.ebay.com/sch/i.html?_nkw=low+temperature+bismuth+solder+paste Something like this: https://www.youtube.com/watch?v=cClPqIJwhLs On the toaster oven, this is how I do BGA reflow on HP JetDirect cards, which use the same bismuth solder paste: http://www.learnbydestroying.com/jeffl/pics/repair/BGA%20reflow/index.html -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#13
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On Friday, August 10, 2018 at 12:23:46 AM UTC-4, Jeff Liebermann wrote:
On Thu, 9 Aug 2018 12:34:54 -0700 (PDT), John-Del wrote: I have an HP34C that I bought new back around 1980 or so to replace my stolen TI SR-51A. It had always been a little flakey but a quick thump brought it back around. A few years later I decided to have a look inside when it required more physical persuasion to behave. I took a picture of the front keys in case they decided to jump out and get mixed up (they did), but I was surprised to find the half dozen ICs *not* soldered down to the flexible circuit board. Yep. It relies on the pressure provided by a foam pad to make the connection. Bad bad bad idea: http://www.hpmuseum.org/hp34.htm They maintain connection by the foam cushion beneath the flex circuit that maintains pressure between the flex circuit and the ICs. I removed each IC, cleaned all the pins and the flex circuit lands, put a tiny bit of dielectric grease on each IC pin, and reassembled. It behaved itself for quite some time. Right now it's been in storage for many years but every once in a while I wonder if the correct solution would be to tack solder them down. I'm sure the foam pad looses a bit of rebound over the years. What do you do when you run across flakey IC contacts in an HP? If the foam pad was in good shape (springy), I would add a 2nd foam pad to give it more pressure. This added pad is rather thin. I should repalce both, but can't find a suitable sheet of foam. I now have access to a laser cutter, so I might be able to cut some foam that will work. I think ordinary soldering is a bad idea and have never tried it. However, if you do decide to try it, I suggest you use low temperature 180C bismuth solder paste, liquid flux, and a temperature controlled toaster oven. https://www.ebay.com/sch/i.html?_nkw=low+temperature+bismuth+solder+paste Something like this: https://www.youtube.com/watch?v=cClPqIJwhLs On the toaster oven, this is how I do BGA reflow on HP JetDirect cards, which use the same bismuth solder paste: http://www.learnbydestroying.com/jeffl/pics/repair/BGA%20reflow/index.html -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 I'm going to dig it out of storage, charge the battery, and see how it behaves. If it behaves, I'll leave it as is. I didn't attempt a resolder back then because I didn't want to modify it and wasn't sure of the flex circuit's response to heat. In later years, I've seen flex circuits (I think they're Kapton) that take soldering heat just fine. I do keep solder paste in stock because I do a lot of smd IC replacement, and mostly use a hot-air station to keep the heat localized. Thanks for the info. |
#14
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On Friday, August 10, 2018 at 7:55:39 AM UTC-4, John-Del wrote:
On Friday, August 10, 2018 at 12:23:46 AM UTC-4, Jeff Liebermann wrote: On Thu, 9 Aug 2018 12:34:54 -0700 (PDT), John-Del wrote: I have an HP34C that I bought new back around 1980 or so to replace my stolen TI SR-51A. It had always been a little flakey but a quick thump brought it back around. A few years later I decided to have a look inside when it required more physical persuasion to behave. I took a picture of the front keys in case they decided to jump out and get mixed up (they did), but I was surprised to find the half dozen ICs *not* soldered down to the flexible circuit board. Yep. It relies on the pressure provided by a foam pad to make the connection. Bad bad bad idea: http://www.hpmuseum.org/hp34.htm They maintain connection by the foam cushion beneath the flex circuit that maintains pressure between the flex circuit and the ICs. I removed each IC, cleaned all the pins and the flex circuit lands, put a tiny bit of dielectric grease on each IC pin, and reassembled. It behaved itself for quite some time. Right now it's been in storage for many years but every once in a while I wonder if the correct solution would be to tack solder them down. I'm sure the foam pad looses a bit of rebound over the years. What do you do when you run across flakey IC contacts in an HP? If the foam pad was in good shape (springy), I would add a 2nd foam pad to give it more pressure. This added pad is rather thin. I should repalce both, but can't find a suitable sheet of foam. I now have access to a laser cutter, so I might be able to cut some foam that will work. I think ordinary soldering is a bad idea and have never tried it. However, if you do decide to try it, I suggest you use low temperature 180C bismuth solder paste, liquid flux, and a temperature controlled toaster oven. https://www.ebay.com/sch/i.html?_nkw=low+temperature+bismuth+solder+paste Something like this: https://www.youtube.com/watch?v=cClPqIJwhLs On the toaster oven, this is how I do BGA reflow on HP JetDirect cards, which use the same bismuth solder paste: http://www.learnbydestroying.com/jeffl/pics/repair/BGA%20reflow/index.html -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 I'm going to dig it out of storage, charge the battery, and see how it behaves. If it behaves, I'll leave it as is. I didn't attempt a resolder back then because I didn't want to modify it and wasn't sure of the flex circuit's response to heat. In later years, I've seen flex circuits (I think they're Kapton) that take soldering heat just fine. I do keep solder paste in stock because I do a lot of smd IC replacement, and mostly use a hot-air station to keep the heat localized. Thanks for the info. I plugged in the old boy and it works perfectly. Even the battery is holding a charge (I changed the cells about 25 years ago when I serviced the flex circuit). Tapping it has no adverse effect on any function, and the keys work perfectly with no lag and no bounce. So the cleaning of the board and chips (and whatever I used for preservative is still holding. There's nothing like the glow of red LEDs either. |
#15
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On Tuesday, August 7, 2018 at 9:24:36 PM UTC-4, Peter Jason wrote:
Unit with charger & owners handbook. Working. Best offer. Peter Hmm..My HP 28S still works fine since the late 80's. Just don't leave batteries in it to degrade. |
#16
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
Ya'll got me thinking.
I bought the HP 35 while I was working for TRW back around 1974. Almost two weeks worth of pay and more than I paid for rent for a month. I also remember at the time, "Reverse Polish Notation? This is a joke isn't it?" http://www.hpmuseum.org/two35s.jpg I bought it from the book store across the street from El Camino College. I have NO idea what ever happened to it. I did by the HP10C when it came out. http://www.hpmuseum.org/10c.jpg I still have it, and a 12C I picked up last year in a thrift store for $5. http://www.hpmuseum.org/12c.jpg -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
#17
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Vintage Hp Hewlett-Packard 25 Calculator with case and charger
On Saturday, August 11, 2018 at 1:54:08 PM UTC-4, Fox's Mercantile wrote:
Ya'll got me thinking. I bought the HP 35 while I was working for TRW back around 1974. Almost two weeks worth of pay and more than I paid for rent for a month. I also remember at the time, "Reverse Polish Notation? This is a joke isn't it?" Back when I was entering college, a scientific calculator was a requirement, and there were several on the recommended list. I narrowed them down to the Texas Instruments SR-51A and the HP (don't remember the model). I bought the SR-51A because I never owned an RPN calculator and figured one less thing for me to learn would be a good thing. The TI was great until a redistributioner relieved me of it. I then bought the HP 34C and became used to the RPN method within minutes. I still would love to have another SR-51A though. Aesthetically, he SR-51A was pretty where the 34C looked so damned professional. I guess it's off to ebay... |
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