[Harp-L] Identifying hazardous amps



Some small amps should be avoided for safety reasons- these are amps built without power transformers. The problem is that it is difficult to install a properly grounded line cord to ground the chassis, so they pose a significant shock risk. It is usually pretty easy to recognize them on inspection because only one transformer is present- it is a output transformer. A another way to identify them is by the tubes. In these amps the tube heaters are wired in series and powered from the 116 V AC wall source. The tubes are typically have have large first numbers, like 50C6, and the sum of the first numbers of all the tubes equals 116. Occasionally, one may encounter an amp with series tube heaters and two transformers. This amp may have an isolation transformer. I believe an amp with an isolation transformer can properly grounded and safely played, but I am not 100% certain of this.

Jim R





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