Changing Vacuum Tubes
| Field | Radio and television repair, computer maintenance |
| Went Obsolete | 1970, but still in wide circulation in some quarters |
| Made Obsolete By | Transistors and integrated circuits |
| Knowledge Assumed | The ability to tell a hot tube from a cold one. Sometimes, the ability to read a tester |
| When useful | When working on vintage electronics, or troubleshooting guitar amplifiers and boutique audio equipment |
The most common vacuum tube fault was the heated filament burning out. Such a tube would no longer glow and be hot. It had to be extracted from its socket and replaced by an equivalent tube. When changing tubes, 1) be certain the equipment is turned off and unplugged; allow several minutes for capacitors to drain, 2) make sure that the tubes are cooled down; vacuum tubes are still in use in high-end audio amplifiers and very popular in guitar amplifiers. If you are changing a power tube on an amplifier, the bias may need to be adjusted; consult the owner's manual for specific instructions for your equipment.
A related obsolete skill was that of repairing ones own vacuum tube television. Well into the 1970's, the owner of a misbehaving TV could remove the vacuum tubes, take them over to the local hardware (or even convenience) store, and plug those tubes into a device that would test them, and identify the tubes that were bad, so that replacements could be bought. The last TV's abandoned tubes around 1975, and the testers disappeared soon after.
Notable Exceptions:
Note that vacuum tubes are alive and well, in 2008, in the musical instrument and high-fidelity audio industry, where some technicians still sell, replace, and bias vacuum tubes on a regular basis. Some antique collectors and dealers can also repair or replace vacuum tubes.