HP Forum Archive 07

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HP-11C Springs Message #1 Posted by Roy on 10 Jan 2002, 10:18 a.m. 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?

Re: HP-11C Springs Message #2 Posted by Raymond Hellstern (Germany) on 10 Jan 2002, 11:43 a.m., in response to message #1 by Roy Hi, AFAIK they force the front and back metal plates to the same electrical potential. Raymond

Re: HP-11C Springs Message #3 Posted by Tony Duell (UK) on 10 Jan 2002, 2:15 p.m., in response to message #1 by Roy 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.

Re: HP-11C Springs Message #4 Posted by David Smith on 10 Jan 2002, 4:29 p.m., in response to message #1 by Roy On some of the HP machines springs are also used to make contact to the piezo beeper disk.

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