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AR-9 front panel attenuator switch


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  • 5 weeks later...



I just started another AR-9 restoration and recap project. I removed the attenuator switch board to take a look at the three switches. I also have a switch I removed from an AR-90 many years ago. The AR-9 and AR-90 switches are identical.


These switches are made by C&K (still in business). Both Mouser.com and Digikey.com sell C&K switches. Both sites have links to C&K datasheets that list the options of each sequence of their part numbers. I went through the datasheets comparing physical characteristics, markings on the switch, and micrometer measurements of the switch I have to identify a part number. 

U211 on the switch indicates it is a UL listed version of the C&K 7211 DPDT (on, on, on) 5A 120VAC switch. Going through each sequence the lever type is “S” (.4206”). The bushing is “Y” (.350” threaded keyway). The termination is “C” (thru-hole in PC board). Contact material is “Q” (Silver plated, standard with C). The 5A, 120VAC rating is also listed here. The last sequence is the seal “E” (it is the only option that produced a valid part number).


I tried various combinations of U211 and did not come up with any switches that were compatible. It looks like this line of switches has been discontinued. But, part number 7211SYCQE is a valid part number and both Mouser and Digikey have them in stock. Instead of being UL listed the 7211 version is RoHS compliant.

One more thing, look closely at how the switches are soldered to the PC board, there is a solder jumper between two of the pins. There is information in the datasheets about using this jumper to make the switch a SP3T switch. This is how it is being used on the AR-9 switch board.

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