HP-28S: Key press problem
06-28-2016, 04:24 AM
Post: #1
 JDW Senior Member Posts: 422 Joined: Jun 2016
HP-28S: Key press problem
I've been using my 28S since 1990 so it shouldn't come as a big surprise it now has a key problem, but I am posting this to see if there is an easy solution. The UP ARROW key is the problem. When the calc is laid flat on a desk, no matter how hard I press that key, nothing happens. But if I press softly on the key front and back, it works fine. Saying it another way... Pressing straight down on the key (the normal way to press keys) does not work, but applying pressure from the top and the bottom (finger pressing on back of calc, directly behind the key) works.

Is this repairable?

Thanks.
06-28-2016, 06:33 AM (This post was last modified: 06-28-2016 06:40 AM by damaltor.)
Post: #2
 damaltor Member Posts: 253 Joined: Dec 2015
RE: HP-28S: Key press problem
Not easily. I guess that the heat stakes holding the keyboard together are broken. As the clamshell calculators cannot be opened without destrying some of the housing, you will have a hard time to repair that.

You will want to read this (not only first post, there are more images following)

edit: here is more
06-28-2016, 06:55 AM
Post: #3
 JDW Senior Member Posts: 422 Joined: Jun 2016
RE: HP-28S: Key press problem
Thank you for the links. But honestly, I would prefer not to have drill holes through the back of my precious 28S!
06-28-2016, 04:38 PM
Post: #4
 damaltor Member Posts: 253 Joined: Dec 2015
RE: HP-28S: Key press problem
Well, then you might be out of luck, as there are afaik no other ways to permanently fix that issue. The heat stakes degrade, and eventually break.
06-28-2016, 11:56 PM
Post: #5
 JDW Senior Member Posts: 422 Joined: Jun 2016
RE: HP-28S: Key press problem
(06-28-2016 04:38 PM)damaltor Wrote:  Well, then you might be out of luck, as there are afaik no other ways to permanently fix that issue. The heat stakes degrade, and eventually break.

Technically, that is true of any plastic part. Which is why I find it very interesting that people pay upwards of $350 for scratched and dented HP-42S's! I can understand the nostalgia, but paying that kind of money for an item that might break due to the sheer age of the plastics is troubling. But in my case, I didn't buy my 28S off EBAY. It was a purchase through my university bookstore back in early 1990. I've used it regularly through the years and only recently noticed the key problem. Thankfully I have a solution. I just need to make a little more effort to press a finger against the back of the case and the key then registers. It would be nice to have it perfect, but in light of how old it is, we can't have it all. Now if we could just figure out how to put a 50G into a more beautiful case, akin to the legacy 48 series, that would be ideal. I'd love to have a modern HP calc with powerful functions and the legacy layout. Who among us wouldn't? Funny HP doesn't recognize that segment of the market. Best wishes. 06-29-2016, 12:16 AM Post: #6  Marcio Senior Member Posts: 438 Joined: Feb 2015 RE: HP-28S: Key press problem (06-28-2016 11:56 PM)JDW Wrote: Technically, that is true of any plastic part. Which is why I find it very interesting that people pay upwards of$350 for scratched and dented HP-42S's! I can understand the nostalgia, but paying that kind of money for an item that might break due to the sheer age of the plastics is troubling.

Hi there,

In case you don't have it yet and are not opposed to using emulators, I highly recommend FREE42. It will save wear and tear on your 28S (money too!). Runs on most modern mobile devices.
06-29-2016, 01:52 AM
Post: #7
 JDW Senior Member Posts: 422 Joined: Jun 2016
RE: HP-28S: Key press problem
Thank you for the kind tip, Marcio. Yes I was aware of the emulator, but there's really nothing like having the actual calc in the hand (at least for people like me).
06-29-2016, 02:40 AM
Post: #8
 Marcio Senior Member Posts: 438 Joined: Feb 2015
RE: HP-28S: Key press problem
(06-29-2016 01:52 AM)JDW Wrote:  ... there's really nothing like having the actual calc in the hand (at least for people like me).

I know. It's very unsettling when the battery dies while you are in the middle of a calculation. Still, a quick (and fast) solution/alternative to having to carry your valuable calc everywhere.
06-30-2016, 10:58 AM
Post: #9
 BartDB Member Posts: 162 Joined: Feb 2015
RE: HP-28S: Key press problem
(06-28-2016 11:56 PM)JDW Wrote:  ...

But in my case, I didn't buy my 28S off EBAY. It was a purchase through my university bookstore back in early 1990.

...

I also purchased my 28S at university. I used it for many years until a few years ago when the battery door just wouldn't hold on anymore.

My personal suggestion for a replacement is to go for the 50g. It takes a bit of getting used to, but has the same stack and programming model as the 28 (RPL).

A 48G series would be the next recommendation, but the 50g is faster, has a bigger screen and has more features (e.g. MDG Metakernel is built-in).

Trying the 42S was frustrating for me:
- stack is limited to 4 levels (frustrating once you're used to the "unlimited" 28/48/50 stack)
- stack lift works differently than 28/48/50 series
- essentially key-stroke programming (and added to that, stack-lift works differently in programs than in normal calculation).

I purchased a 42S but sold it again as I felt it was not worth the investment as I only ended up using it for quick calculations and found a cheaper 32s was just as useful. I do use Free42 for on-screen calculations.

I have since bought a very good condition 28S off eBay, but have not gone back to it. The 50g is my main work horse. I use a 32s just for quick calculations because it is smaller & lighter (I am keeping an eye on the DM42 to replace the aging 32s).

06-30-2016, 11:51 AM (This post was last modified: 06-30-2016 12:34 PM by Marcio.)
Post: #10
 Marcio Senior Member Posts: 438 Joined: Feb 2015
RE: HP-28S: Key press problem
(06-30-2016 10:58 AM)BartDB Wrote:  I purchased a 42S but sold it again as I felt it was not worth the investment as I only ended up using it for quick calculations and found a cheaper 32s was just as useful. I do use Free42 for on-screen calculations.

HP should have invested a lot more on the hardware that was supposed to replace both the 15C and the 41C. While the 42S did bring many more features and ease of use, the hardware was not so much. I have seen many people complain about that, from faulty keyboard to low quality LCD display with dying pixels. It's all documented in the archives of the old forum.

I think the DM42 will have a *much* better and DURABLE hardware. The software is state-of-the-art already. The ability to import and export programs is one of the best features of Free42, in my opinion. Let's hope the DM-42 has it too.
06-30-2016, 12:02 PM
Post: #11
 JDW Senior Member Posts: 422 Joined: Jun 2016
RE: HP-28S: Key press problem
Bart, thank you for your informative post. I found it very helpful. It's also interesting to hear that Meta Kernel is built into the 50G out of the box. Did you also install SpeedUI on your 50G?

Marcio, I agree that the DM42 looks to be a very interesting slim-line RPN calc. I am just curious how the developer profits from these devices seeing they all require custom made plastic molds. To get your ROI on the molds alone you'd need to sell an awful lot of them.
06-30-2016, 01:42 PM
Post: #12
 BartDB Member Posts: 162 Joined: Feb 2015
RE: HP-28S: Key press problem
(06-30-2016 12:02 PM)JDW Wrote:  Bart, thank you for your informative post. I found it very helpful. It's also interesting to hear that Meta Kernel is built into the 50G out of the box. Did you also install SpeedUI on your 50G?

As far as I know SpeedUI is only for the 48G series (best on the 48GX with extra RAM card, although selected components can be installed on a G or G+ and some have even hacked a G or G+ to add more RAM).

06-30-2016, 01:58 PM
Post: #13
 rprosperi Super Moderator Posts: 5,285 Joined: Dec 2013
RE: HP-28S: Key press problem
(06-30-2016 10:58 AM)BartDB Wrote:  - essentially key-stroke programming (and added to that, stack-lift works differently in programs than in normal calculation).

Can you elaborate on how stack-lift differs between programs and manual calculations? I've never heard this regarding the 42S, and it seems contradictory to the very nature of keystroke programming.

--Bob Prosperi
06-30-2016, 06:55 PM
Post: #14
 damaltor Member Posts: 253 Joined: Dec 2015
RE: HP-28S: Key press problem
(06-30-2016 01:58 PM)rprosperi Wrote:
(06-30-2016 10:58 AM)BartDB Wrote:  - essentially key-stroke programming (and added to that, stack-lift works differently in programs than in normal calculation).

Can you elaborate on how stack-lift differs between programs and manual calculations? I've never heard this regarding the 42S, and it seems contradictory to the very nature of keystroke programming.

yup, i would be interested in that, too.

other than that: if you come from the 28, skip the 48 and go for the 50. the 48 is great, i have three and i love them. but compared to the 50g, it is PAINFULLY slow, especially the G (not GX) versions, as they stop for a few seconds from time to time to garbage collect. the 50g is freaking fast. as you have to learn a new keyboard layout anyway, you can go for the 50g.
the keyboard of the 48g is superior though, but the keyboard of the 50g is not that bad - at least not as bad as the 49g.
06-30-2016, 11:56 PM (This post was last modified: 07-01-2016 12:08 AM by JDW.)
Post: #15
 JDW Senior Member Posts: 422 Joined: Jun 2016
RE: HP-28S: Key press problem
Thank you for the recommendation on the 50G, damaltor. By the way, have you used or been tempted to use "Tree Browser" on your 50G or any of the software add-ons by Andreas? I've asked this in other threads but no one replies to me. Makes me wonder why. I understand the software isn't free and the author locks it down to a single device, but the software looks interesting nonetheless, and I've love to hear actual user experiences about it.

It was mentioned that "SpeedUI doesn't work on the 50G." Is this due to the fact that code written for the 48 isn't compatible with the 50? Or is it because something similar is already incorporated into the 50 and therefore SpeedUI is no longer needed?

Thank you.
07-01-2016, 02:03 AM
Post: #16
 rprosperi Super Moderator Posts: 5,285 Joined: Dec 2013
RE: HP-28S: Key press problem
(06-30-2016 11:56 PM)JDW Wrote:  It was mentioned that "SpeedUI doesn't work on the 50G." Is this due to the fact that code written for the 48 isn't compatible with the 50? Or is it because something similar is already incorporated into the 50 and therefore SpeedUI is no longer needed?

Basically, both. SpeedUI is written in low level SysRPL and assembler and is closely tied to the 48GX ROM; it will not run on anything else (possibly including a 48G due to limited ram, though I imagine a 48G+ will work).

The 50g is sooo much faster than any 48 that SpeedUI is not needed.

--Bob Prosperi
07-02-2016, 04:20 PM
Post: #17
 damaltor Member Posts: 253 Joined: Dec 2015
RE: HP-28S: Key press problem
JDW: No, sorry. i never used it.

rprosperi: you are right - on a plain 48g there is not enough room for all speedui libs. a gx will work, though i had a lot of problems installing it so i went for metakernel - which is preinstalled on the later calculators.
07-24-2017, 10:58 AM
Post: #18
 beerlim Junior Member Posts: 7 Joined: Jul 2017
RE: HP-28S: Key press problem
On my 28S I have the following issue.
During the keyboard test I noticed that the whole row 'Y' to '(' and 'EVAL' to '-' are not responsive at all.
Any suggestions?
07-25-2017, 01:36 AM (This post was last modified: 07-25-2017 02:15 AM by Jlouis.)
Post: #19
 Jlouis Senior Member Posts: 705 Joined: Nov 2014
RE: HP-28S: Key press problem
[quote='beerlim' pid='76485' dateline='1500893921']
On my 28S I have the following issue.
During the keyboard test I noticed that the whole row 'Y' to '(' and 'EVAL' to '-' are not responsive at all.

I had this problem in my 28s. It is fixable, but you have to open the calculator and change some heat stakes. As I was not secure if I could do the job, so I send mine to an expert in HP, he did the fix and gave me back with a perfect battery door , for the original was already broken!

There are tutorials for fix this problem, I'm not sure in the old forum or find a good repair expert in HP. Is Fixthatcalc still active?

Edit: I forgot to mention, the fix did not affected the exterior of the calculator, it is like new now, perfect. The 28s is one of my preferred calculator, due its former factor and the alpha keyboard, very useful and elegant. The only thing is that HP could have made it with the alpha keyboard on the right side, as some Sharps.
07-25-2017, 01:48 AM (This post was last modified: 07-25-2017 01:51 AM by Jlouis.)
Post: #20
 Jlouis Senior Member Posts: 705 Joined: Nov 2014
RE: HP-28S: Key press problem
(07-02-2016 04:20 PM)damaltor Wrote:  JDW: No, sorry. i never used it.

rprosperi: you are right - on a plain 48g there is not enough room for all speedui libs. a gx will work, though i had a lot of problems installing it so i went for metakernel - which is preinstalled on the later calculators.

Is Metakernel pre-installed on the 48's later calculators?

I think this is not true, as I have some of the last ones, black LCD, from 2001, 2002 and there's no MK.