Vintage Hp Hewlett-Packard 25 Calculator with case and charger

[Peter Jason]

Unit with charger & owners handbook. Working.
Best offer.
Peter

[Fox's Mercantile]

<https://en.wikipedia.org/wiki/HP-25>


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

[Peter Jason]

On Tue, 7 Aug 2018 20:30:56 -0500, Fox's
Mercantile <jda...@att.net> 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/

[Jeff Liebermann]

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 je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Michael Black]

This is for the repair of electronic equipment. It's not a buy and sell
newsgroup.

Michael

[Rheilly Phoull]

At least it's not political :-)

[Jeff Liebermann]

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.

[John-Del]

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?

[John-Del]

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...

[peterw...@gmail.com]

Oh, I dunno - there is a certain elegance to "loosing" a rebound.

Peter Wieck
Melrose Park, PA

[John-Del]

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.

[Jeff Liebermann]

On Thu, 9 Aug 2018 12:34:54 -0700 (PDT), John-Del <ohg...@gmail.com>
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>

[John-Del]

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.

[John-Del]

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.

[Ancel B]

Hmm..My HP 28S still works fine since the late 80's. Just don't leave batteries in it to degrade.

[Fox's Mercantile]

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>

[John-Del]

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...