Testing Radio And TV Tubes

Vacuum tubes, used in almost all electronic devices prior to 1958 and still extensively used into the 1970s, performed amplification or signal-processing functions in everything from computers to radios to televisions to radar and avionic equipment. Made largely obsolete by transistors and later by integrated circuit designs, tubes had to be checked and replaced periodically.

Prior to 1970, almost every town in the United States had somewhere one could buy replacement vacuum tubes. If the television wasn't operating properly, you would open the back of the set, pull some or all of the tubes out of their sockets, cart them down to the radio or TV store or even many drugstores and Radio Shacks, and there would be a “tube tester” near the display of replacement tubes. The tester had several dozen sockets, labeled as to which type of tube it would accept and test. One by one, you plugged in the tubes, a meter or lamps on the tester would indicate if the tube was performing within acceptable limits, and tubes which failed could be replaced right out of a rack nearby.

As more and more electronic gear went to transistor and integrated circuits, which did not fail in the same way as tubes, tube testers disappeared from drugstores along with the racks of replacement tubes. Eventually, almost all domestic production of vacuum tubes ceased during the late 1980s, though Eastern Europe still had some factories making them.

Vacuum tubes continue to be extensively used in guitar and stage amplifiers, as well as audiophile stereo equipment. However, tube testers are almost impossible to find and usually are in the hands of professionals who service such equipment.