Hi all,

I have a Curta II that would often input the wrong numbers...

I tried lubing with sewing machine oil and it helped but quickly returned to its error prone self.

I bought a cheap ultrasonic cleaner from Amazon and cleaned the unit using water and dish soap. A fair amount of gunk came out. Then I dried it using a hair dryer. I used Mobius oil to lube the sliders and points I could get to. (I only took the bottom two screws off when I cleaned the calculator so I really couldn't oil all the points that require further disassembly)

I couldn't be happier, the curta hasn't had an error yet after lots of calculations. It feels really smooth now.

I would have expected this post on 04/01.
I would never think of cleaning a Curta in water and washing-up liquid - more like kerosene.
There are now many places in your Curta that no longer have a suitable lubricant. There are tiny springs and steel balls in the input slides in a bore that is certainly difficult to get the water out of. I always disassemble newly purchased Curtas down to the last part, clean the individual parts in an ultrasonic bath with petroleum and then lubricate them with the right lubricants according to the service manual when assembling them. In some cases parts have to be replaced or adjusted. Your approach is not the best for such a precision mechanical machine.

UPDATE: More than a year later and my Curta still works perfectly after the cleaning.