The Museum of HP Calculators

HP Forum Archive 21

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On calculator preservation (LCD darkening, pouches...)
Message #1 Posted by Marc Ferrer (France) on 3 Dec 2012, 5:37 a.m.


This post is slightly off-topic since not directly linked to HP. I'd like to share some experience and eventually get some advice from you fellow collectors, so here it is :

Yesterday, I pulled out most of my calculator collection from its boxes. Besides the pleasure, I wanted to check a particular machine : a few years ago my Sharp PC-1211 LCD began darkening on its left side (a well-known problem specific to displays from that era). To my relief the phenomenon didn't scale up since last year, the computer is still usable. Alas, I discovered 2 other Sharps now suffering from the same disease : a PC-1251 and a PC-1245.

Then some facts surprised me :

1. The 3 machines are "attacked" at the LEFT side of the display. They were stored vertically, standing on their RIGHT side.

2. The problem shows up on two different generation displays : the earlier ones with a yellow filter (1211), and more recent, grey-looking ones (1245-1251).

3. It doesn't show up on the HPs, Casios and TIs I also own. Very brand-specific.

Until now I thought that only the early displays were prone to such failure, I was wrong. Now, considering that the machines were vertically stored, and darkening from the "up" side : could it be related to some fluid leaking at a "molecular" rate ? I remember having read that the sealing process of these displays is critical.

Anyway, my collector's purpose is to delay this darkening from growing up, if it's possible. I'm about to store the machines horizontally, but I fear that it makes the displays darkening from everywhere... Well, I'm not sure it has anything to do with gravity.

What do you think of that ? Surely there are chemists, physicists and process engineers among you all. I'd be very glad to hear from you. Even if deteriorating is irreversible, knowing why is always interesting.

I'll end this post with another bad discovery I made : some pouches (all brands, but especially the wallet-shaped and/or oldest ones) begin to exhibit the problem we all face with the "gummy wheels" ! Some of them get sticky when held in hand more than a few seconds, some are "oily". By chance I've always been storing then apart from the machines. It's the best we all can do.

Thank you for reading ! Best regards, Marc

Re: On calculator preservation (LCD darkening, pouches...)
Message #2 Posted by Keith Midson on 3 Dec 2012, 6:22 a.m.,
in response to message #1 by Marc Ferrer (France)

I've had a few calculators with this disease. The Sharp PC-1211 is a common sufferer - it had one of the first LCD displays. The yellow display didn't survive well in UV light and was easily damaged, resulting in LCD leakage. I'm not sure if the way you store them has much to do with it - it's probably more related to where the sun's rays hit the screen in its early years of use. I have a mint 1211 in my collection HERE - I live in fear that one day i'll pull it out and it will have a leaky screen. I've only had one HP with a leaky screen - a 10C. It was in perfect condition when I bought it, and then one day it had a good third of the screen with leaked LCD. I sold it for a fraction of what I bought it for and got a new one ... I have no idea what caused that. It was stored in a dark/ dry cupboard. Cheers, Keith

Re: On calculator preservation (LCD darkening, pouches...)
Message #3 Posted by Frank Boehm (Germany) on 3 Dec 2012, 6:40 a.m.,
in response to message #1 by Marc Ferrer (France)

I don't think that the orientation will have any influence.
Most likely, the "seal" (small bulky spot, like plastic) is on the left side due to manufacturing. This is the weakest spot.
Different manufacturers certainly used different types of glue to seal the display, obviously, they are not equally good at keeping O2 and humidity away.
Unfortunately, the process is - to my knowledge - irreversible (though it might be possible to separate both halves, replace the liquid crystal fluid and seal them again - that's not easy and expensive and not worth the trouble for these calculators...)
Best way to store them? I'd say cold, very low humidity (sealed bag with silica gel).
The cases are a common issue, it's best just to keep calculator and case apart.

Re: On calculator preservation (LCD darkening, pouches...)
Message #4 Posted by Bart (UK) on 3 Dec 2012, 6:45 a.m.,
in response to message #1 by Marc Ferrer (France)


I have had one PC-1251 develop that problem. It happened during a cold winter period and it was unfortunately stored in a room that was not properly heated, so it may have experienced temperatures as low as -5 deg. C. I am not sure if this contributed to the problem. However, I have seen a number of PC-1251's on ebay with this problem, so they seem to be susceptible to screen leakage and I think all were from the left. I now keep my calculators in a better controlled environment to reduce anything that can cause additional stress on the old screens.

Edited: 3 Dec 2012, 6:53 a.m.

Re: On calculator preservation (LCD darkening, pouches...)
Message #5 Posted by Marc Ferrer (France) on 4 Dec 2012, 8:01 a.m.,
in response to message #4 by Bart (UK)

Hello Keith, Frank and Bart,

Thank you :-)


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