What should be my next LED HP calculator?

[Steve Simpkin]

(12-05-2021 04:06 AM)Trond Wrote:  Bumping this thread to update: I finally got myself an HP-55

Now there's a slight issue; the machine looks very good for its age, but all the decimal point lights will sometimes flash up. Has anyone experienced this before? Some bad connection somewhere perhaps? Otherwise it seems to work just fine.

As Teenix mentioned, from page 91 of the HP-55 Owners Handbook.

https://literature.hpcalc.org/community/hp55-oh-en.pdf

[Trond]

Many thanks!
Battery is completely dead after I left it for a while on the charger(!)

BTW how long does it normally take to charge?

[Steve Simpkin]

(12-05-2021 05:16 AM)Trond Wrote:  Many thanks!
Battery is completely dead after I left it for a while on the charger(!)

BTW how long does it normally take to charge?

With the original capacity NiCad batteries it took about 14 hours to fully charge (page 86). Have these batteries been replaced recently? If they are very old they may not be able to hold a charge.

[Trond]

They look new to me. Hmm, I should have left it on the charger overnight. I'll put it on the charger now for a good while and see what happens.

In good news, there was an ugly "scratch" in the glass that at first made me go "oh well, old calculator". Then it turned out that the scratch was a tiny bit of glue (or something like that) that I managed to wipe off. Now it looks near mint

[vaklaff]

(12-05-2021 03:37 PM)Trond Wrote:  In good news, there was an ugly "scratch" in the glass that at first made me go "oh well, old calculator". Then it turned out that the scratch was a tiny bit of glue (or something like that) that I managed to wipe off. Now it looks near mint

Congrats but where is the photo? :-)

[Trond]

I'll post photos when I know I'm keeping it

It looks like there is a bad connection to the batteries.
Batteries that work in my HP67 do not work in this one.
Which is a bad sign.

[teenix]

(12-05-2021 07:41 PM)Trond Wrote:  I'll post photos when I know I'm keeping it

It looks like there is a bad connection to the batteries.
Batteries that work in my HP67 do not work in this one.
Which is a bad sign.

Simple possibilities are corrosion on the battery contact faces, the shorting link in the battery charger socket has corrosion, the power switch contacts need cleaning from inside.

These are all easy to fix if that is the problem.

If the calculator was showing the low battery intermittently when moved, then maybe the battery contacts need a gentle bend upwards to make them have more pressure on the battery contacts.

If you try this, put finger or finger nail pressure just after the contact bend where it enters the calculator casing to hold it steady and provide a bend point. Then gently lift the outer end up a bit.

Failure to do similar to this may break the contact mounting inside the calculator which is a simple plastic heat stake.

cheers

Tony

[Trond]

Well, this is weird. I put my old batteries from the HP 67 into the 55, and vice versa.....and now (for the moment at least) they're both working perfectly!

OK here it is:

[Trond]

By the way, I'd be interested to know if you have a way of programming pseudo-random numbers with this one.

[vaklaff]

(12-05-2021 11:02 PM)Trond Wrote:  Well, this is weird. I put my old batteries from the HP 67 into the 55, and vice versa.....and now (for the moment at least) they're both working perfectly!

OK here it is:

Sigh, I shouldn't have asked for a picture, now I want a 55 too...
Anyway, congrats to the recovery!

[Steve Simpkin]

(12-06-2021 03:21 AM)Trond Wrote:  By the way, I'd be interested to know if you have a way of programming pseudo-random numbers with this one.

From page 20 of the HP-55 Statistics Programs book. The book is available at the following link.

https://literature.hpcalc.org/community/...tat-en.pdf

[Trond]

(12-06-2021 08:08 AM)vaklaff Wrote:  

(12-05-2021 11:02 PM)Trond Wrote:  Well, this is weird. I put my old batteries from the HP 67 into the 55, and vice versa.....and now (for the moment at least) they're both working perfectly!

OK here it is:

Sigh, I shouldn't have asked for a picture, now I want a 55 too...
Anyway, congrats to the recovery!

Many thanks! I'm liking this one more and more, despite the lack of continuous memory. Maybe it will be my "bedside drawer" calculator for quick number crunching and conversions when I need it.

The old HP 67 battery I already had is a contraption with lots of tape and such. I think the slight pressure that come from the thickness of the tape when closing the lid did the trick for the 55 somehow. Remarkably, the battery that came with the 55 actually fits better in the 67. Just one of those lucky breaks. I hope it holds up.

[Trond]

(12-06-2021 08:34 AM)Steve Simpkin Wrote:  

(12-06-2021 03:21 AM)Trond Wrote:  By the way, I'd be interested to know if you have a way of programming pseudo-random numbers with this one.

From page 20 of the HP-55 Statistics Programs book. The book is available at the following link.

https://literature.hpcalc.org/community/...tat-en.pdf

This is good stuff. Interesting that it includes Bayesian inference as well, I don't think I have that in my other HP books. Thanks Steve!

[BobVA]

(12-06-2021 06:26 PM)Trond Wrote:  ...I'm liking this one more and more, despite the lack of continuous memory. Maybe it will be my "bedside drawer" calculator for quick number crunching and conversions when I need it....

I've always had a soft spot for the 55. Using HP's excellent brochure as a reference I wrote a lot of programs for it while in high school, despite it being *way* out of my financial reach. I finally got to try them out when I got an HP-25 just before heading to university :-)

The 25 has more sophisticated programming, but the stopwatch capabilities on the 55 are still impressive.

If you're going to use it infrequently, consider making up a battery pack using low-self discharge Ni-MH batteries, like Panasonic Eneloops.
For intermittent use, three Eneloop AAA batteries in a holder would give you months of use before you have to recharge them. If you do this, use an external AAA charger. Katie's instructions here show how to build one.

[Dave Britten]

(12-07-2021 04:38 PM)BobVA Wrote:  If you're going to use it infrequently, consider making up a battery pack using low-self discharge Ni-MH batteries, like Panasonic Eneloops.
For intermittent use, three Eneloop AAA batteries in a holder would give you months of use before you have to recharge them. If you do this, use an external AAA charger. Katie's instructions here show how to build one.

I second that, grab one of these, and use your choice of AAA charger:

https://www.ebay.com/itm/323932408596

That's what I use in my 65, 45, and 80, and a similar homemade version in my TI-59. Modern AAA NiMHs will generally run the calculator longer than old NiCd AAs from the 1970s.

I'd love to get ahold of a 55, since it has built in unit conversions and linear regression - and the stopwatch is a nice addition - but the price and lack of int/frac functions has held me back thus far. Maybe one of these days when I'm not spending all of my money on ham radio stuff...

EDIT: And the lack of engineering display mode would be hard to swallow.

[Trond]

(12-07-2021 04:38 PM)BobVA Wrote:  

(12-06-2021 06:26 PM)Trond Wrote:  ...I'm liking this one more and more, despite the lack of continuous memory. Maybe it will be my "bedside drawer" calculator for quick number crunching and conversions when I need it....

I've always had a soft spot for the 55. Using HP's excellent brochure as a reference I wrote a lot of programs for it while in high school, ....

What brochure? Do you have a PDF?

[BobVA]

(12-07-2021 10:39 PM)Trond Wrote:  

(12-07-2021 04:38 PM)BobVA Wrote:  I've always had a soft spot for the 55. Using HP's excellent brochure as a reference I wrote a lot of programs for it while in high school, ....

What brochure? Do you have a PDF?

I wish I had an original brochure! There's a nice scan available in the "Advertisement and Brochures" section of the Museum CD set