How to clean the display of an 11C?


I have an HP 11C that has got dust in the display:
under the glass, and above the LCD. Some of the dust
specks are fairly large and unsighty. How do I clean it?
I tried to take it apart, and I can remove the back
cover, but I cannot get to the display due to the
heat-fused stakes (bad design, if you ask me).
Would a blast of compressed air from a can be of any use?
It's not obvious where to blow it, though.
Does anyone have other suggestions? I don't feel
that I am good enough to drill all the heatstakes, and
then re-glue them. I am pretty sure I would end up with
a mess.





I had the same problem with one of my Pioneers. I used compressed air from a can, and it worked great. I blew the air around the edges, and it eventually removed the dust. I think the dust particles are attached to the display with nothing more than static electricity.



I thought the heat-stakes only welded the key moulding to the key-contact PCB. I've never pulled one apart but I have a description from someone who has. It implies that the LCD/logic assembly can be detached from the keyboard PCB.

Maybe this will jog the memory of someone who has dismantled it.



There are several different versions of the Voyagers. The earliest models (I think these existed as 11C and 12C only)
had a removeable logic/display module based on a flexible PCB. The keyboard PCB was heat-staked to the top case, but the logic would just lift out once you took the bottom case off. And of course it was easy to clean the LCD.
Later versions have one PCB carrying the logic chips, display and keyboard contacts. This PCB is heat-staked to the top case. With this design it's possible to replace chips, etc with the PCB still in place, but to get to the display
you have to undo the heat staking, repair the fault, and then fix the PCB back in place.
I'd try yhe can of compressed air that other have suggested before trying to remove the PCB.


I had a problem with a standard TI-92 (not the Plus) and eventually convinced TI that the micro code was screwed. They sent a brand new replacment. If you have seen the screen on a TI-92 you know it is fairly large. I had already finished a class and really shouldn't have opened it but I couldn't resist trying a couple of formulas that wouldn't work correctly on the original machine and see if it got different results. Much to my surprise, it did. And they were understandable and correct. Well needless to say that was less than 30 minutes to 1 hour usage. I used it again about 2 times for a total of 3 hours all together. I picked it up the other day and started to put it up for sale and noticed something. Yes, sitting there looking back at me was a little screen booger. They visited me ever now and then on the original unit, stayed about 1 or 2 months or 1 or 2 hours, and left. I believe it is lint that is in the environment where either the components are assembled or the final assembly is done. There is no doubt they are all the same and love static electricity. They change shapes sometimes and then move around a little or not at all and eventually disappear. All components of a calculator should be cleaned and moved to a clean room and then assembled. Then this wouldn't happen.


I once cleaned the display in my 15C by VERY carefully lifting/peeling the brushed aluminum metal "bezel" (?) off the unit. HP attached it with clear double-sided adhesive tape to the plastic housing. The outer plastic protective lens comes away with it, providing acces to remove any annoying dust particles between it and the LCD. There is also a small spring between the circuit PC board and the aluminum bezel, presumably for grounding and static protection. I then put it back on with new pieces of double sided tape. Although this may pose a greater risk of cosmetic damage, I think it poses a lesser risk of electronic damage, when compared to major disassembly of internals.

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