Disassembling dusty HP27S

[erwin]

I bought a very dusty HP27S, where dust came inside and reduces the visibility of the display. In my opinion the one possibility to clean is to open the calculator, but I couldn’t find any way without applying brut force. So I gave up.

Is there an easy procedure for opening available.

Erwin

[Randy]

Opening it will not get you any closer to the display, it's behind the logic board. The best way to clean is a couple of cycles through an ultrasonic cleaner. If that is not available, form a point on the end of the tube on an air blaster can. Stick the point in the case seam and blast away. Work from both sides and you should be able to get most of it out. It can be VERY stubborn.

Don't use any mechanical methods, you'll only scratch the inside of the lcd or polarizer, they are very soft materials.

[Matthias]

Well, I´m a layman in ultrasonic cleaning. As I know, you put the dirty unit in the cleaner and fill it with undistilled water. But what happenes with the electonic parts in the calculator? Does the water damage the electronical parts? What is "allowed", what is "not allowed", because you damage parts?

Matthias

[Randy]

The water will not damage anything.

So long as you always remove batteries and when cleaning is done you shake out all excess water and dry in a warm place all you will get is a clean calculator.

[erwin]

Thank for helping