[Test-Equipment] HP buttons

[Adrian Godwin]

J.Forster wrote:
> Try rubber cement thinner (Heptane). It is pretty easy to get and dissolves
> grease pretty well. It also does not attack most plastics. It is very flamable,
> so be careful.
> 
> -John
>

I had some isopropyl alcohol which is probably even less agressive, and
since no-one had warned me I might mess the buttons up I had a go.

The button mechanisms are quite odd : they have a rectangular base with
the contact area covered and an external spring that changes from a
simple curve to an S shape when the button is pressed.
It's fairly easy to remove this spring, and I found that cleaning the 
back of it sorted out the problem. However, it soon returned unless I 
also cleaned the plastic base : it seems that the lubricant (or some 
other deposit) sticks the spring to the base.

Some of the buttons were less accessible, so I gave up removing the
spring and just washed the whole base off with alcohol. After drying,
this worked fine. However, there are some rust spots on some of the
springs so I was wary of leaving them completely clean and unprotected.
I therefore sprayed them lightly with switch cleaner : the oil
in this will probably eventually gum up again, but if it lasts
even a fraction of the 20 years they've lasted so far, I shan't mind.

-adrian