[Harp-L] Identifying hazardous amps

[Dina Janzen <dlj@xxxxxx>]

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