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Comparing the Collins 75S-3B and 75S-3C Receivers

Written By: Ron Baker / WB4HFN

There was recently a lot of discussion over identifying an original production Collins 75S-3C receiver over an upgraded 75S-3B.    For the older "B" version Collins produced an upgrade kit for the end user to install and as a factory upgrade.   The discussion was initially trying to determine a fair market value for the 75S-3C receiver, which lead to determining whether the receiver was an original or an upgraded version.    The original "C" version is assumed to have a high value over the older "B" version, even with the "C" version upgrade.    Listed below are several points to consider when determining which model or variation you have. 

There are five major areas of differences which have been identified.  Keep in mind there may other differences not listed here, and possibly other variations of those that are listed.     

1)  The Eye-Brows:  In most cases the 75S-3B had the narrow eyebrow, whereas the 75S-3C had the much wider eyebrows around the Preselector dial. The 75S-3B upgrade to a C would still have the narrower eyebrows. There possibly was some exceptions, it was suggested that Collins may have did a special production run of the C model using narrow eyebrow panels to take care of a backlog of orders.

2)  The Escutcheon Plate: the converted C model would still have the B series model number on the plate or a small label plate with the C model number glued over the original B model number. The exception here may be a new C series escutcheon plate was purchased from Collins and installed along with the conversion. However, the conversion kit sold by Collins did not include a C model escutcheon plate.

3)  Serial Number Plate:   The upgraded B would still have the original 75S-3B model listed on the serial number plate, the original C model would have the correct model number listed.

4)  Front Panel Silk Screening:  On the B model the front panel was directly silk screened with the band selector switch position indicators. On the C model the front panel silk screening was left blank, instead the band switch information was silk screened on the small escutcheon panel attached to the band switch knob shaft. The B model upgrade would still have the original front panel silk screening on the front panel itself. The exception to this could be the special production run situation as described earlier.

5)  Crystal Sockets:  On the B version the band switch crystal socket was mounted on top of the chassis. The B upgrade kit installed the second crystal bank socket on the bottom side of the chassis. The original C model this was reversed, standard ham band crystal socket for bank #1 was on the bottom and the bank #2 accessory crystal socket was mount on the top of the chassis. This gave easy access to plug in the accessory crystals.

6) Top Level Part Number:   The receivers all carry a "top level part number" which is the Collins part number for the complete receiver.  It will either be stamped on the top of the chassis or be on a piece of aluminum foil that is glued to the chassis, similar to the way the serial number is indicated.   The number for the 75S-3B is 522-3316-000 and the number for the 75S-3C is 522-3317-000.