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Not long ago I mentioned in a thread that I once had a 48sx that had been stolen when my home was burglarized some years back.

I discovered this past weekend that indeed it wasn't. The 48sx was found in a box that a friend had packed for me during a move. That was great news! Smile The bad news: unfortunately it has been in a storage facility for the last ten years. While I was happy to find it, I wasn't optimistic that it would be functional. The storage facility isn't climate-controlled, and for the last ten years everything in it has been subjected to the heat/cold/humidity/dust extremes that are common to those types of units.

When I got it home, the first thing I checked was the battery compartment. Unfortunately, there were three alkalines left in it. There was obvious corrosion damage from the leaking cells. I also had a 32K memory card in it, but fortunately there was no battery installed for that. The card showed no signs of problems when I removed it.

The entire body (including the display) had areas of mildew and other debris, so I spent some time attempting to clean it up. I was able to remove much of it, but the paint on the faceplate has several areas where the paint has started flaking off and/or has some other abnormality.

I then focused my attention on the display, which has a discolored area in the lower left quadrant of the screen. Close inspection showed that the area of concern was not on the surface, but rather embedded in the screen itself. Not a good sign:
[Image: 01_display_off.jpg]


I figured I would try to power it up just to see what would happen, so I installed a fresh set of batteries. To my utter amazement, it powered up successfully in the usual manner. The "F" key worked to clear the memory at the "Try to recover" prompt, and I was presented with the usual setup. So far, so good:
[Image: 02_empty_stack.jpg]


The next step: check the keys and load some things on the stack to see what happens. It was evident very quickly that the display problem was related to the actual LCD pixels themselves. Unfortunately, the pixels in the affected area are non-functional:
[Image: 03_stack_full.jpg]


Filling the display with dark pixels shows more clearly the extent of the damage:
[Image: 04_all_dark.jpg]


...and a close up of the damaged area:
[Image: 05_closeup.jpg]


I'm guessing that the only way to clear this up would be to replace the display, but I'm certainly open to trying any suggestions others may have to see what happens. I suspect that replacing the display is beyond my personal skill level, and likely would cost more than it's worth for someone else to do it. So I'll probably just live with it as-is.

Amazingly, all the keys worked flawlessly. Given all the external blemishes caused by the mildew, I was very surprised that the keyboard seemed no worse off than the last time I used it 15 years ago.

After running some of the internal diagnostics, I powered it off and inserted the RAM card. The card seems to work without problems, though I need to get a battery for it to see if it maintains its integrity when not powered from the calculator.

Apart from the damaged screen (and a missing IR/Port cover), the calculator seems to function normally. I was even able to restore a ca. 1995 backup to it that I found on an old data CD. It was interesting to see what I had been using on the 48 at the time -- it was like stepping into a time machine for a few minutes as I re-discovered what I had been doing. I'm starting to have a better understanding of those who have extensive collections of these things. The memories it caused went well beyond the programs I had been using.

(edited to update image links)
There's nothing like finding lost treasure in the form of an old friend from the past.

It looks like the screen was damaged by something organic rather than totally ruined pixels. I wonder if the layer of polarized plastic is damaged and can be replaced.

Good luck in the restoration.

Brad
(07-08-2014 10:48 PM)Brad Barton Wrote: [ -> ]It looks like the screen was damaged by something organic rather than totally ruined pixels. I wonder if the layer of polarized plastic is damaged and can be replaced.

I had the same thought when I looked at the area with a 17x loupe. I've seen some instructions for disassembling the 48, but haven't yet run across anything that describes whether the display layers can be easily separated. If anyone has any insight, please share!

One of my bigger concerns with opening the unit is the potential for causing flaky connections with the keyboard and/or display pads in the process. Even if I were to get the display "crud" cleared up, I think it would be a net loss if I ended up with keyboard or display row/column faults as a result. If I were already having those types of issues in addition to the display problem, the decision to open it up would be easier.

Perhaps I should just try to find a non-working "for parts only" 48 for practice and spares. I'll consider that option as well.
Here is a minimally intrusive technique that you may want to try: leave the calculator out in the light. Recently, I received a rather nice HP 21s with some black blotches seemingly embedded in the LCD. The display was still usable, but unsightly. I took it to work and left it out on my desk for convenient use. After a week, I noticed the blotches were disappearing. After a month, the blotches were gone.
I remember that people recommended extended sun exposure for photographic lenses that had suffered fungal growths. Perhaps some blemished LCD displays will respond to similar treatment?
Direct sunlight or will it work if the calculate under a little shade be alright?
(07-09-2014 06:52 PM)everettr Wrote: [ -> ]Here is a minimally intrusive technique that you may want to try: leave the calculator out in the light. ... Perhaps some blemished LCD displays will respond to similar treatment?

It's certainly worth trying, and easy enough to do. I'll probably just leave it out of the case pointing the screen toward a south-facing window most of the time, and then occasional periods of direct sunlight. I'm reluctant to leave it in direct sunlight for extended periods, though.

Thanks for the suggestion!
(07-09-2014 07:28 PM)Eddie W. Shore Wrote: [ -> ]Direct sunlight or will it work if the calculate under a little shade be alright?

As I am a contractor, my desk is well away from the windows, :-) , so there was no direct sunlight involved in my case, just rather bright fluorescent lighting. I think that I would only try direct sunlight if normal indoor lighting or indirect sunlight did not work. Lenses seem to be much more robust than LCDs. I would worry about the LCD getting hot in direct sunlight.
I'd go for the fungus treatment.

The blotches pretty clearly do not line up with the pixels, so I suspect something in the covering of the display, rather than a deterioration of the display itself.
(07-09-2014 09:23 PM)DavidM Wrote: [ -> ].

Sorry for gravedigging, but did it work?
(04-13-2017 06:05 AM)pier4r Wrote: [ -> ]
(07-09-2014 09:23 PM)DavidM Wrote: [ -> ].

Sorry for gravedigging, but did it work?

The best, Pier, in this beloved forum is that gravedigging, often you find answers to your actual questions Smile Smile
(04-13-2017 06:05 AM)pier4r Wrote: [ -> ]Sorry for gravedigging, but did it work?

I tried exposing the display to increasing amounts of sunlight (even extended periods of direct) over the course of several weeks. It never got any better, and the only difference I could ever see was perhaps a very slight change in shape of some of the branches of the "blob". The coloring and nature of the spot(s) makes me more inclined to think that its cause was a physical leakage of some sort as opposed to fungal/organic.

Sometime last year I purchased a cheap 39g with the intent of doing a display transplant, but never got around to attempting the operation. It's still on my "stack of projects" to be revisited at some point, but not until I clear out some of the more important ones first. Smile
(07-08-2014 08:35 PM)DavidM Wrote: [ -> ]... the display, which has a discolored area in the lower left quadrant of the screen. Close inspection showed that the area of concern was not on the surface, but rather embedded in the screen itself. Not a good sign:
[Image: 01_display_off.jpg]
...
That is a leak of the liquid crystal, possibly due to freezing or a direct impact. I actually got to witness this effect as it grew and spread over time in the display of an HP 200LX palmtop. There is an animated gif (link below) of the process recorded over 9 days through a USB microscope at about 10x magnification.

http://www.striegels.com/alan/HPLX/200lx_screen/LCD_leak_growth.gif

Alan
(04-13-2017 04:39 PM)striegel Wrote: [ -> ]
(07-08-2014 08:35 PM)DavidM Wrote: [ -> ]... the display, which has a discolored area in the lower left quadrant of the screen. Close inspection showed that the area of concern was not on the surface, but rather embedded in the screen itself. Not a good sign:
[Image: 01_display_off.jpg]
...
That is a leak of the liquid crystal, possibly due to freezing or a direct impact. I actually got to witness this effect as it grew and spread over time in the display of an HP 200LX palmtop. There is an animated gif (link below) of the process recorded over 9 days through a USB microscope at about 10x magnification.

http://www.striegels.com/alan/HPLX/200lx_screen/LCD_leak_growth.gif

My second HP-48GX and my HP-200LX are unusable due to dark spots. I had already replaced the screen of the latter because of the same reason.

[Image: IMG_3079_zpsrkj4axhh.png]
Gerson! I saw the first time the bigger version in your picture in high school, when the team of our school trained for the national Olympiad of physics! The professor took out this fatty semi laptop that turned out to be a big calculator (that evening used only for simple arithmetic).

I was ecstatic but I did not pay too much attention to it because we started to crack problems (that evening we did only 3, with 5 people. One of which went on to win the gold medal, in the Olympiad of mathematics, in my country. Nevertheless he was not selected for the IMO team. So far the only true gifted person that I met in person)

Anyway it was exactly the same model that you have on the left.... no wait, it was a TI calculator, I remember the logo. Did the TI have a similar model?
(04-13-2017 07:25 PM)pier4r Wrote: [ -> ]Anyway it was exactly the same model that you have on the left.... no wait, it was a TI calculator, I remember the logo. Did the TI have a similar model?

This one, perhaps? 'Similar' might sound heretic, though.

[Image: 92-big.gif]
definitely that one. Thanks!
(04-13-2017 06:35 PM)Gerson W. Barbosa Wrote: [ -> ]My second HP-48GX and my HP-200LX are unusable due to dark spots. I had already replaced the screen of the latter because of the same reason.

I have an old rubber-key 49G relegated to the shop that began to develop a dark spot on the screen. I kept the calculator in a case with a magnetic clasp on the front, and I noticed the spot was roughly beneath the magnet. Thinking that might be the cause of the spot, I started returning the calculator to the case facing backwards. Sure enough, after a few months the spot went away.

Anyone hear of magnetic fields affecting the liquid crystal material of a display?
~Mark
I picked up a 200lx not too long ago and its screen is bad too. I haven't had much luck finding any kind of replacement.

I pull me 48sx out of the drawer every now and then and try to remember how to do things and then get side tracked on some other project or life in general and it doesn't get used for a while again.

Like you said though, its hello old friend, its what taught me the math I needed to survive college since they expected you to know a lot already from high school.
(04-14-2017 03:01 AM)mfleming Wrote: [ -> ]Anyone hear of magnetic fields affecting the liquid crystal material of a display?
~Mark

I wouldn't think the magnetic field would directly affect the LCD material, but perhaps it's a mechanical effect?

Maybe the magnet (or whatever it sticks to) is applying some pressure to a point on the LCD panel when the case is closed? Plastic LCD's are pretty sensitive to pressure, so even a tiny amount over a long time might cause some artifact on the display.
I had a similar issue on two (!) navigation displays on my motorcycle, both replaced under warranty. The number of bad pixels continued to increase, in a chained fashion, as your picture shows. My bike hadn't seen any temperatures outside -20º to 38º C, and the display was protected behind another plastic window, so there was no impact damage. I even talked to the manufacturer, and the representative said the displays should have handled that temperature range.
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