HP-11C Springs

[Roy]

I opened the back of an HP-11C to view the circuit board.
I noticed two very small springs of unequal length in molded
towers vertical to the circuit board. They must touch the
back cover when it is closed. Does anyone know the purpose
of these springs?

[Raymond Del Tondo]

Hi,

AFAIK they force the front and back metal plates to the same electrical potential.

Raymond

[Tony Duell]

Those springs electrically connect the metal plate on the back of the machine, the metal bezel round the display and the metal plate around the keys. These
plates then form a sort of Faraday cage around the logic board, presumably for static protection and/or reducing RF emissions.

[David Smith]

On some of the HP machines springs are also used to make contact to the piezo beeper disk.