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Cam switches: Difference between revisions
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A benefit of this design is low parasitics compared to traditional rotary wafer switches. | A benefit of this design is low parasitics compared to traditional rotary wafer switches. | ||
The original idea for this switch type is credited to [[Howard Vollum]] - see [[Patent US 3562464A|Patent 3,562,464 ''Cam actuated switch having movable and fixed contacts on circuit board'']] (Vollum, Verhoff, Sprando). | The original idea for this switch type is credited to [[Howard Vollum]] - see [[Patent US 3562464A|Patent 3,562,464 ''Cam actuated switch having movable and fixed contacts on circuit board'']] (Vollum, Verhoff, Sprando). [[Ken Holland]] was also involved with the development of cam switches at Tek. | ||
From ''[https://vintagetek.org/wp-content/uploads/2019/06/On-The-History-And-Environment-Of-Tektronix.pdf On The History and Environment of Tektronix]'': | From ''[https://vintagetek.org/wp-content/uploads/2019/06/On-The-History-And-Environment-Of-Tektronix.pdf On The History and Environment of Tektronix]'': | ||
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</blockquote> | </blockquote> | ||
[[ | There were different forms of contact fingers in use. | ||
The basic type, as described in the patent drawings (also in use in the [[back-lit switches|back-lit pushbuttons]] have a contact spring on a post soldered into the board. | |||
Another type, used in high-frequency attenuators types, has a spring riveted to the board, with a small multi-fingered, gold-plated contact spring element isolated by a molded plastic assembly. In these, the spring is typically grounded, and the isolated contact fingers bridge adjacent pads when actuated. | |||
Some switch assemblies also have contacts on the opposite side of the PCB, actuated via small plastic plungers. | |||
Finally, the [[067-0587-02]] plug-in uses a special [[Media:7104_maintenance.pdf|elastomer-based cam switch]] | |||
==Maintenance== | ==Maintenance== | ||
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==Pictures== | ==Pictures== | ||
'''Drawings''' | |||
<gallery> | |||
Cam switch core.png | Core of the cam switch | |||
Basic cam switch contact.png | Basic switch contact with solder post (shown in alignment jig) | |||
Isolated cam switch contact.png | Isolated contact type used in attenuators | |||
Elastomer cam switch contact.png | Elastomer contact used in [[067-0587-02]] | |||
</gallery> | |||
'''Photos''' | |||
<gallery> | <gallery> | ||
Tek 7a19 frontright.jpg | Cam switch in [[7A19]] | Tek 7a19 frontright.jpg | Cam switch in [[7A19]] | ||
Tek 7a19 rearright.jpg | Cam switch in [[7A19]] | Tek 7a19 rearright.jpg | Cam switch in [[7A19]] | ||
Tek 7a19 att sw3.jpg | Cam switch in [[7A19]] | Tek 7a19 att sw3.jpg | Cam switch in [[7A19]] showing isolated contact fingers | ||
Cam-01.jpg | Cam switch with contacts on both sides of the PCB ([[7D15]]) | Cam-01.jpg | Cam switch with contacts on both sides of the PCB ([[7D15]]) | ||
Cam-02.jpg | 7D15 double-sided switch | Cam-02.jpg | 7D15 double-sided switch | ||