HP-48GX key stiffness

[anyfoo]

Hello,

I recently got my first HP-48GX ever, also the first HP calculator of that era that I ever used. I think I lucked out a bit: It has a serial number starting with ID21 (so one of the later issues, I think), a high contrast black LCD, and looks like new. There is some tiny indication that it may have been used at all, but if so, it's been taken very good care of.

The only thing which I'm wondering about is the keys. Besides some light creaking, they are primarily very stiff. They seem to work flawlessly and give a good click as confirmation, but I feel that I need to use more force to engage them than I needed on most other non-cheap calculators so far.

Are they just that stiff and creaky, or is there a potential problem?

[Raymond Del Tondo]

(06-08-2020 10:59 PM)anyfoo Wrote:  Are they just that stiff and creaky, or is there a potential problem?

Do you have other HP calcs to compare the key stiffness?
For the creaky sound: Do all keys make that noise?
Or could it be the housing itself?
Are there signs of dirt in the gaps beteen the keys and the faceplate?

[anyfoo]

(06-09-2020 12:59 AM)Raymond Del Tondo Wrote:  Do you have other HP calcs to compare the key stiffness?

No. This is my first one of that era.

Quote:For the creaky sound: Do all keys make that noise?

"More or less", as in, some more, some less. I feel as if the bottom keys are a bit less creaky.

Quote:Or could it be the housing itself?

It's hard to tell, but I feel like the housing is actually making a different creaky sound. The one from the keys is more high pitched. Could be wrong, however. And I don't mind the sound, I'm just not sure if they keys behave as they should.

Quote:Are there signs of dirt in the gaps beteen the keys and the faceplate?

Not really!

[Steve Simpkin]

I find my HP-48G keys are a little bit stiffer than the keys on my HP-25 or HP-12C. They are a whole lot stiffer than the typical TI, Casio or Sharp calculator keys which are for the most part, mushy. The creaky sound is most likely from small gaps in the housing where the top and bottom halves of the calculator meet. Mine tends to creak more when pressing the upper 5-6 rows of keys and there is almost no creak sound when pressing the bottom two rows. I think what you are describing is fairly normal for a 20+ year old 48 series model.

[anyfoo]

Thanks, that does make sense. Guess I'll just have to get used to it.

[GreyUser]

It was made in 2002, IIRC the 48G series was discontinued in 2003. So, it’s a late model made in Indonesia. Some of the units made in Indonesia suffer from an annoying trait of having noisy or clicking keys, that is they make more audible noise on the keypress than is typical for the design. There is absolutely nothing wrong with the unit functionally, they just make a different kind of click sound when the key dome collapses and makes contact, registering the keypress. No one seems to really know the cause of the differences, it may be a keyboard part variation or a process variation or perhaps a combination of both.

They only way to know if your’s is “normal” is to compare it to another, similar unit, most desirably made in Singapore. A 48S or SX would be the gold standard for comparison as they were only made in Singapore.

In general, the HP calculators of the era require more force to actuate the keys than the vast majority of the other calculators in the market as the others use use soft, rubber dome keys without the positive tactile feedback of the HP design. Once you get used to the HP keyboard and RPN, you’ll either never go back or you’ll end up selling the GX because you just can’t or don’t want to adapt. You’ll either love it or hate it.

[Steve Simpkin]

There is a great article on the design of the HP-48S/G models in this June 1991 issue of HP Journal.
http://hparchive.com/Journals/HPJ-1991-06.pdf

[Joe Horn]

(06-09-2020 01:44 AM)GreyUser Wrote:  A 48S or SX would be the gold standard for comparison as they were only made in Singapore.

Not all of them. I have a 48 SX right here in my hand which says "MADE IN USA" next to its serial number 3024A00764. In case it matters, it has ROM version D.

[GreyUser]

Interesting, didn’t know they built the first 48’s in Corvallis. Makes sense since it was just a stretched Pioneer, keyboard wise.

The big brown beasties had those crazy tab package CPU’s as well. I always got a chuckle over the black plastic stick-on covers over the cpu die due to the light sensitivity. I guess the comm port was large enough to let enough visible light in that the engineers decided it needed to be addressed. The attention to detail back then was just ingrained in the corporate culture, due in part to the fact that the founders initials were an acronym for High Priced ;-)

[mfleming]

(06-09-2020 05:01 AM)GreyUser Wrote:  The attention to detail back then was just ingrained in the corporate culture, due in part to the fact that the founders initials were an acronym for High Priced ;-)

No no no, High Performance, dangit. High. Performance.

[cdmackay]

I'm lucky to have two late Indonesia 48GXs, serial ID237xxxxx, and neither seem particular clacky, or stiff. Indeed, I'd say my 15C was stiffer, and my 50g much more so.

So whatever it is, it doesn't affect all late ID examples.

hopefully it doesn't detract from the pleasure of using it, glad to hear it's working well.

edit: perhaps a closer comparison, my 32SII is much stiffer than either 48GX.

[anyfoo]

Thanks everyone, really insightful.

Since RPN was mentioned above: Besides already being an owner of HP Prime (in RPN mode) beforehand, and doing some semi-extensive use of both HP-48GX and HP-50g emulators, I have also been using emacs-calc for years, so I know that RPN is right for me.

As for the key click: It overall sounds like that's just how HP-48GXs are, with mine in particular being of an even more clicky variant perhaps. cdmackay, you say your Indonesian model does not exhibit this, but what are you relating your observation to? As I said, this is the first HP calculator of that era I've ever used, so I don't know what is the expected amount of force.

[cdmackay]

(06-11-2020 01:07 AM)anyfoo Wrote:  As for the key click: It overall sounds like that's just how HP-48GXs are, with mine in particular being of an even more clicky variant perhaps. cdmackay, you say your Indonesian model does not exhibit this, but what are you relating your observation to? As I said, this is the first HP calculator of that era I've ever used, so I don't know what is the expected amount of force.

I was comparing mine to my other HP cals, in particular the 15C, 32SII & 50g. My two 48GX keyboards seem better than all of those. My 15C/32SII are older than the 48GX, the 50g newer.

[anyfoo]

After playing around a bit more with it, I've got to say... my HP-48GX really needs a lot of force to press the keys. It's hard to imagine that other calculators need even more force?

Yet there isn't any "mushiness" or anything else in the feel that would suggest that the keyboard has an issue.

[cdmackay]

(06-12-2020 08:05 PM)anyfoo Wrote:  After playing around a bit more with it, I've got to say... my HP-48GX really needs a lot of force to press the keys. It's hard to imagine that other calculators need even more force?

that sounds really odd; my 48GXs have very light keys; the other calcs are heavier, but it's all relative.

Once conferences start happening, you might want to go to an HP one, and compare yours with others' ; or find an enthusiast in your area…

[anyfoo]

For anyone caring, I just got an HP-48SX off eBay (to repair, but the keyboard itself seems fine), and it does feel different from my late Indonesian HP-48GX. Softer and quieter.

I'm not too bothered however, my HP-48GX works very well, and continues to look like new. In fact, I bought the broken 48SX so that I could open another one without feeling too bad about it.

[Steve Simpkin]

(03-27-2021 04:40 AM)anyfoo Wrote:  For anyone caring, I just got an HP-48SX off eBay (to repair, but the keyboard itself seems fine), and it does feel different from my late Indonesian HP-48GX. Softer and quieter.

I'm not too bothered however, my HP-48GX works very well, and continues to look like new. In fact, I bought the broken 48SX so that I could open another one without feeling too bad about it.

It's interesting that there is a difference in the key press feel and sound between HP-48 models. I have a USA HP-48SX from 1991 and a Singapore HP-48G from 1994. I always thought there was a slight difference in the way the keys felt and sounded but they are very similar. My HP-48G does creak more.

Here is more information on how to disassemble an HP-48 from Han Duong.
https://web.archive.org/web/201309151722...uong/open/

[anyfoo]

(03-27-2021 06:35 AM)Steve Simpkin Wrote:  Here is more information on how to disassemble an HP-48 from Han Duong.
https://web.archive.org/web/201309151722...uong/open/

Thanks, that's the instructions I already found and followed. And I still managed to butcher it, effectively. HP really, really did not mean for those things to be opened.

In the end, I'm not too sad about it, because it turns out that while the board is fine (and I saved it), the keyboard assembly was almost fully soaked in leaked battery gunk, which is almost certainly the problem anyway.

A broken board I could probably have repaired, a broken keyboard assembly less so, especially since it seems to be another unopenable sandwich.

But this makes me wonder whether I should ever buy another HP-48 series to repair, since I'm obviously not convinced I can open it without at least some cosmetic damage. I successfully repaired an HP-15c without issue, and it is now my "daily driver" besides my working HP-48GX. And that latter one will be left unopened forever.

[franz.b]

(03-27-2021 07:45 PM)anyfoo Wrote:  Thanks, that's the instructions I already found and followed. And I still managed to butcher it, effectively. HP really, really did not mean for those things to be opened.

In the end, I'm not too sad about it, because it turns out that while the board is fine (and I saved it), the keyboard assembly was almost fully soaked in leaked battery gunk, which is almost certainly the problem anyway.

A broken board I could probably have repaired, a broken keyboard assembly less so, especially since it seems to be another unopenable sandwich.

But this makes me wonder whether I should ever buy another HP-48 series to repair, since I'm obviously not convinced I can open it without at least some cosmetic damage. I successfully repaired an HP-15c without issue, and it is now my "daily driver" besides my working HP-48GX. And that latter one will be left unopened forever.

I have opened and repaired a 27s that has the keyboard made in the same way, and it is repairable.
https://www.hpmuseum.org/forum/thread-16265.html

[anyfoo]

(03-28-2021 07:48 AM)franz.b Wrote:  I have opened and repaired a 27s that has the keyboard made in the same way, and it is repairable.
https://www.hpmuseum.org/forum/thread-16265.html

Thanks. I had since already completely taken it apart and also noticed that it would be repairable. The leaking battery corroded the conductive ink on the sheet of paper that provides the key contact circuits, and it seems feasible to maybe even just redraw it using conductive ink.

So I think I could put it back together eventually, but since I have a working HP-48GX already I'm not super motivated (maybe to resell it cheaply to someone who wants a HP-48S without paying the usual premium prices). Right now the board+display sits otherwise fully functional on my desk, after I cleaned the corrosion off and soldered a cable to the keyboard contacts to "remote control" it. I think it makes for a good hardware test bed when I e.g. build my own RAM card (being an 48S it has no slots but the contacts for it).