Traditional colour display tubes (CRTs) have three electron guns: one each for red, green, and blue. As the tube ages, the electron emission of these guns may degrade due to contamination of the cathode or deterioration of the electron-emitting coating. Given the cost of replacing a failing tube, television repairmen would sometimes attempt to “rejuvenate” a failing electron gun by running it at an elevated filament voltage and zapping the cathode with a pulse of high voltage in the hope of burning off contamination. Sometimes this worked, and sometimes it wrecked the CRT, but with a failing CRT, there was nothing to lose by trying.
In this episode, a Sony Trinitron monitor rescued from a dumpster with a failing green channel is diagnosed and subjected to the rejuvenation treatment. Will the zap fix it?