Well over 30 years ago, as a young TV test technician, I had applied to work for a well-known German TV maker. As part of the qualification evaluation process for this position, I was asked to troubleshoot a newly fabricated set in which a number of faults had been intentionally created. A full set of schematics and appropriate test instruments were provided.
One by one, I had found and corrected a number of faults. Ultimately, all the signals on the CRT socket, including the HV terminal and the deflection coils, were as expected. Yet I still could not get a picture. In fact, the CRT face remained completely dark. Evidently the electron beam was somehow failing to reach the phosphor. One of the common causes of this is a misalignment of the ion trap located on the neck of the CRT. This ion trap consists of a small bar magnet that is typically secured on the neck with a hose clamp.
Moving the ion trap back and forth along the neck and even turning over the magnet did not help at all. So, I was then suspecting that the CRT was actually defective. When I so indicated to the fellow who had been watching over the troubleshooting process, he picked up a screwdriver and showed me that the "magnet" had in fact no magnetization at all! That was something I had never experienced before, nor since, but it was a great lesson about not assuming anything. While I failed to find the magnet that wasn't, I still got the job.
This entry was submitted by Alain Gronner and edited by Rob Spiegel.
After completing an EE degree and apprenticeships in both the instrumentation and the telecommunication industries, Alain Gronner started and ran his own manufacturing company, which developed and produced instrumentation for the US telephone digital network.
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