FT-243 Crystal Socket

thingiverse

Many ham radio operators have a stash of old style crystals mounted in FT-243 holders that were made by the millions during WWII and since. But even though the crystals are common the molded plastic crystal sockets made for them have become scarce. So here is a 3D printed socket that works just like the old ones did although the PLA material cannot tolerate the heat the old thermoset plastic ones did. The solution is to heat-sink the terminal while soldering using a pair of forceps or needlenose pliers and to solder quickly to avoid melting the plastic. The pins on FT-243 crystals are the same diameter as octal tubes that were in widespread use at the time, and thus the sockets used the same contacts used in octal tube sockets. The 3D printed socket does also, so an old octal socket with this type of contact will have to be sacrificed, but they are much more common than crystal sockets! It might be possible to fashion a copy using something like .010” thick brass shim stock cut and bent appropriately. Each metal contact has a small “V-shaped” notch stamped through it which is bent outward after insertion into the socket to hold the contact in place. This indentation can be easily straightened-out with needlenose pliers and the contact can be easily pushed out. After the contacts are re-inserted into the new crystal holder the V can be re-bent if desired but it probably will be held tightly enough without doing so. The contacts can also be bent to the side for retention. The 3D printed socket is mounted to the panel with a single #4 screw just like the original. A detailed description of the contacts required and how they are installed can be downloaded from the Attachments link at the bottom of this article: https://tinyurl.com/2p973sr7 Since PLA cannot tolerate heat as the original thermoset molded sockets could, soldering should be done very quickly and ideally, after attaching a heat-sink such as a pair of forceps or needlenose pliers where the contacts emerge from the housing.