If you're talking about the Messenger Two then that would be a 12BW4 rectifier tube.
If the radio works without it then I'd check the bottom and see if someone hasn't replace the tube with a couple of silicon diodes.
73 Richard WB8KRN

"ac5tx" wrote in message news5kSb.4557$EW.2301@okepread02...
Please tell me the number of the tube for the Johnson Viking Messenger CB radio located in the back of the radio, far right corner looking from the front. Mine is missing and I have no manual or schematic. Thanks a lot.