rjr@mgweed.UUCP (Bob Roehrig) (05/24/85)
The chassis of many brands/models of TV sets is "hot". That is, One side of the AC line cord is set "ground" or common. This is especially true these days in the 12" B&W portables except those that also have a 12 VDC input. My RCA XL-100 has a power transformer, which you would normally think would serve as an isolation device but this is not necessarily true. In my set, the primary is tapped and used in autotransformer style to develop a couple hundred volts for the deflection circuits. Thus, one side of the line cord goes directly to the chassis! The audio output IC is direct coupled to the speaker, so there is no isolation via any output transformer either. I ended up adding a small 1:1 audio transformer and had to place it as far away from the deflection yoke as possible to avoid picking up the strong field from it. One quick way to tell if this is a problem with your set is to check each side of the power plug to circuit common, or metal chassis with an ohmmeter. Bob K9EUI