HP-48's display with an unusual(?) stain

[vaklaff]

Hello

I got hold of a 48 with a stain. Its nature is new to me:
display on
display off
The look of it changes from black to light grey (even a bit glossy), depending on the viewing angle and light.

It doesn't look to me like a case of the "display bleed" (that would be more compact and always black) nor the usual "polariser rot" (that would be circular and placed in the middle). I suspect it's dirt or something directly on the LCD's surface or in the layers above. More likely the latter, i think I can see a shadow cast by the stain like there's some depth beneath it. But then how could that something get there? The layers are pressed together, aren't they? There are no traces of the calculator ever being opened.

Has anyone experienced that? Any advice how to deal with it?

TIA
v.

Edit: Grammar

[cruff]

The LCD panel is failing. Nothing you can do but replace it with a good one.

[vaklaff]

(09-24-2023 04:17 PM)cruff Wrote:  The LCD panel is failing. Nothing you can do but replace it with a good one.

Oh well. Thanks for the assessment. By the way, what's exactly happening there, does it have a name?

I happen to have a battered 48G that can serve as a donor but opening the 48 seems to be for the brave only:
https://www.youtube.com/watch?v=3roTLMhoBOM

[DavidM]

That display artifact appears very similar to an issue I had with a 48sx shown in this thread. I tried several things, none of which helped in any way. Ultimately the display was swapped with one from a 39g, and you can see the result in that thread.

I don't use that calculator very often now, but I'm always impressed at how aesthetically pleasing the black pixel display is with the color scheme of the 48sx, which IMHO has the best color choices of the series.

[rprosperi]

(09-25-2023 11:39 AM)DavidM Wrote:  ...I'm always impressed at how aesthetically pleasing the black pixel display is with the color scheme of the 48sx, which IMHO has the best color choices of the series.

Sorry, no 'like' button available here... yes, I agree fully; an HP-48SX with a black LCD is the best looking of all calculators!

[Massimo Gnerucci]

(09-25-2023 12:08 PM)rprosperi Wrote:  

(09-25-2023 11:39 AM)DavidM Wrote:  ...I'm always impressed at how aesthetically pleasing the black pixel display is with the color scheme of the 48sx, which IMHO has the best color choices of the series.

Sorry, no 'like' button available here... yes, I agree fully; an HP-48SX with a black LCD is the best looking of all calculators!

[vaklaff]

(09-25-2023 11:39 AM)DavidM Wrote:  That display artifact appears very similar to an issue I had with a 48sx shown in this thread. I tried several things, none of which helped in any way. Ultimately the display was swapped with one from a 39g, and you can see the result in that thread.

Indeed, thanks! I can't see your pictures there but that GIF is definitely what I'm seeing here as well, albeit without any progression.

The black display is damn nice :-) I have a 39gs somewhere without any actual use that I might sacrifice without much grief. Is its display compatible with the 48?

[DavidM]

(09-25-2023 01:06 PM)vaklaff Wrote:  Indeed, thanks! I can't see your pictures there but that GIF is definitely what I'm seeing here as well, albeit without any progression.

Apologies... I've updated the image links in the posts that I can edit and hopefully you'll be able to see them now.

(09-25-2023 01:06 PM)vaklaff Wrote:  The black display is damn nice :-) I have a 39gs somewhere without any actual use that I might sacrifice without much grief. Is its display compatible with the 48?

Not sure about the 39gs. Perhaps someone else can chime in?

Also, I have to say that the picture of the updated 48sx doesn't quite do justice to the actual appearance. Seeing it in person, it just seems like the way the 48sx was meant to be. It's frustrating to see the normal blue/green display I have on my 48g now.

[rprosperi]

The 39gs is NOT compatible with the 48SX/GX. That is an ARM device and is quite different size, interface, etc.

Compatible with 48: 48S/48SX/48G/48GX/39G/40G/49G (39G/40G/49G have Black LCD)

(Note that most late (2001+) 48GX from Indonesia also came with a Black LCD)

Not compatible with 48: 39g+/39gs/40gs/48gII/49g+/50g


(Thanks to Paul Berger for straitening me out on this years ago)

[cruff]

(09-25-2023 10:10 AM)vaklaff Wrote:  Oh well. Thanks for the assessment. By the way, what's exactly happening there, does it have a name?

"LCD rot" is one term used to describe it. It is caused by delamination or other breakdown of the panel's structure, possibly caused by extreme temperature, humidity or physical stresses. Once started it tends to get progressively worse. I had this happen on two navigation displays on my Goldwing, I could track the progress of the failure as more pixels started dying. You can imagine an automotive display has to withstand even harsher conditions than a calculator!

[Ren]

(09-25-2023 11:49 PM)cruff Wrote:  I had this happen on two navigation displays on my Goldwing,

Goldwing?
What kind of calculator is that?
B^)

[Steve Simpkin]

(09-25-2023 12:08 PM)rprosperi Wrote:  

(09-25-2023 11:39 AM)DavidM Wrote:  ...I'm always impressed at how aesthetically pleasing the black pixel display is with the color scheme of the 48sx, which IMHO has the best color choices of the series.

Sorry, no 'like' button available here... yes, I agree fully; an HP-48SX with a black LCD is the best looking of all calculators!

I have always thought so too but I am biased for using my HP-48SX as my primary calculator for over 27 years. Of course, HP gave the color scheme a great deal of thought.

From the Industrial design of the HP-48SX:
   

HP Journal magazine June 1991

[franz.b]

(09-24-2023 11:37 AM)vaklaff Wrote:  Hello

I got hold of a 48 with a stain. Its nature is new to me:
display on
display off
The look of it changes from black to light grey (even a bit glossy), depending on the viewing angle and light.

It doesn't look to me like a case of the "display bleed" (that would be more compact and always black) nor the usual "polariser rot" (that would be circular and placed in the middle). I suspect it's dirt or something directly on the LCD's surface or in the layers above. More likely the latter, i think I can see a shadow cast by the stain like there's some depth beneath it. But then how could that something get there? The layers are pressed together, aren't they? There are no traces of the calculator ever being opened.

Has anyone experienced that? Any advice how to deal with it?

TIA
v.

Edit: Grammar

In my opinion it seems to look a lot like the fungi or mold that develop in old photographic lenses. The problem is understanding which of the layers of the display it develops in, because it could be easily removable if it is on an external surface under the polarized plastic layer that should be replaced.
Bye.

[vaklaff]

Thanks for all the replies. Looks like there’s no other way than to open the machine and start from there. If I manage not to break it for good, of course :-) Wish me luck!

Is Han’s Opening the HP48 the current state of art? I managed to open and fix a Pioneer but this thing is a completely new level…

[mfleming]

My personal opinion, for what it's worth. I've used the "rip a phone book in half" method on several 48's. Very easy to mess things up, particularly the first time, by bending the inner metal frame or other damage. The reassembled case never quite feels the same as before, in some instances the two halves are noticaby loose. If ever I find a reasonably priced 48SX (inflation. Meh!) I'll try the remove the faceplate with a heatgun/hairdryer approach. A much less savage way to access the heat stakes holding the case halves together.

[Kiwi]

(09-25-2023 11:21 PM)rprosperi Wrote:  The 39gs is NOT compatible with the 48SX/GX. That is an ARM device and is quite different size, interface, etc.

Compatible with 48: 48S/48SX/48G/48GX/39G/40G/49G (39G/40G/49G have Black LCD)

(Note that most late (2001+) 48GX from Indonesia also came with a Black LCD)

Not compatible with 48: 39g+/39gs/40gs/48gII/49g+/50g


(Thanks to Paul Berger for straitening me out on this years ago)

The HP38G is also a good donor (but it will not be a black LCD).

[rprosperi]

(09-26-2023 12:59 PM)Kiwi Wrote:  

(09-25-2023 11:21 PM)rprosperi Wrote:  The 39gs is NOT compatible with the 48SX/GX. That is an ARM device and is quite different size, interface, etc.

Compatible with 48: 48S/48SX/48G/48GX/38G/39G/40G/49G (39G/40G/49G have Black LCD)

(Note that most late (2001+) 48GX from Indonesia also came with a Black LCD)

Not compatible with 48: 39g+/39gs/40gs/48gII/49g+/50g


(Thanks to Paul Berger for straitening me out on this years ago)

The HP38G is also a good donor (but it will not be a black LCD).

Dang, I missed that one!! Above list now corrected. Though I guess most will understand if I don't think about the 38G much...

Thanks Kiwi!

[vaklaff]

(09-25-2023 11:49 PM)cruff Wrote:  "LCD rot" is one term used to describe it. It is caused by delamination or other breakdown of the panel's structure, possibly caused by extreme temperature, humidity or physical stresses.

Thanks for the details!

As if on cue, this new eBay item looks affected as well:
https://www.ebay.com/itm/225791907157
If you have a suitable spare display, you can build your own black-display 48SX! Maybe you can talk the seller to a discount by pointing to this thread :-)

(I'm in no way affiliated with the seller)

[vaklaff]

(09-26-2023 08:14 AM)vaklaff Wrote:  Thanks for all the replies. Looks like there’s no other way than to open the machine and start from there. If I manage not to break it for good, of course :-) Wish me luck!

Is Han’s Opening the HP48 the current state of art? I managed to open and fix a Pioneer but this thing is a completely new level…

TL;DR: I was lucky and replaced the rotting display.

Details:

I went through the document and watched HP 48G+ gets repaired!. (Many thanks to the authors if they read this!). I decided to use wooden sticks from the best ice cream bar ever made as the prying tools, I thought they would unlikely leave dents.

Opening went rather well, except for the bottom part where I lost patience and just tear the calculator apart. Fortunately not much damage done, I just broke a few of the rivets keeping the keyboard and metal frame together.

First of all I "fixed" the connection between the keyboard and the PCB: just added a thin foam strip on top of the original rubber strip. It looked already deformed and aging. I hope the added strip will postpone the usual keyboard problems I saw on some 48 machines.

Then I replaced the display with a HP40's one. I spent more than an hour on aligning the display, the conductive strips and the PCB. That was the most frustrating part. The display and the strips have too much free space around and you have no clue if they are all aligned correctly. It's just trial and error. Fortunately there was a happy end after all, the new display caught up.

The fixed GX next to a G+ which has the same display the GX had: https://i.imgur.com/PovYkbr.jpeg
The idea was to get rid of the display rot in the GX but getting a much better display is indeed a nice bonus :-)

Looks like the few broken rivets aren't that much of a problem, the keyboard passes the self-test and feels normal and uniform.

Just for fun I tried to get to the blemish ("rot") in the old display but didn't succeed. The layers stick together too firmly.

Lessons learned:

• Have patience when opening a 48, follow Han's document to the letter.
• Even more patience is needed when positioning the new display. Try and try again.
• Always have a few ice cream bars around, they can be of great help!
• I'm not going to put a black LCD into my pristine SX. Too risky and too much effort just to have the best looking of all calculators. I'm not sure it's true anyway ;-)
  

Edit: typos