HP Forums

I wanted to share yesterday's experience with you all. Recently I bought an HP 28C in good condition from TAS.



In good condition at least visually and fully working. But acoustics ..! The hinges of the folding mechanism felt annoyingly sticky with a terrible squeaking and creaking sound.

It is not necessary to open the calculator case. A small drop of my preferred bike chain wax lube did a perfect job.



Applied 8 drops of lubricant onto the 4 hinges front and backside. Then worked it into the gaps with a piece of paper. The lube will penetrate, build a thin film and is well suited for plastics.

Opening and folding the 28C is now very smooth and silent. Since I don't want to promote any product I didn't include a brand name. Any wax or Krytox based bike chain lubricant will do; just stay away from oil or WD40.

Just in case

Patrick

Hello!

I don't know... I rather let mine squeak as I think it is part of the original design and the special (or only) charm that these calculators have to offer :-) An LED calculator has to glow in the dark an an HP "clamshell" calculator has to squeak.

And also the connecting cables between the two keyboards go through those hinges. If on a hot day that lubricant gets really liquid and finds it's way along the cables and into the connectors then the calculator might not only not squeak but also not work any more.

Regards
Max

(08-25-2018 01:18 PM)Maximilian Hohmann Wrote: [ -> ]I don't know... I rather let mine squeak

:-) To each his own.
The amount of lube penetrating into the hinges is so tiny, it hardly will make its way to any of the electronics. In addition to that wax based lube is an insulator and the cable connector between the two pcbs is isolated.

I'm usually too busy lamenting the awful battery door to notice any creaking.

My 19BII mostly just stays on my desk at home for tax/finance work. They're just too fragile for me to justify carting it around, especially when my 200LX can do almost anything the 19BII does (plus loads more).