Hello to the list.. I am changing my,newly acquired, 75A-4 S-meter potentiometers to the improved version. I can not seem to locate a source for the screw driver adjust slot in the shaft or the proper size pot. If anyone on the list knows a source for these or has a pair they would sell I would appreciate your letting me know ! The value of both controls is 500 ohms. Thank you for your help. 73 Merle W1GZS