Quote:
Originally Posted by Electronic M
The isolation transformer is for the power connection for the set. Most sets without an internal power transformer have one side of the cord connected directly to the chassis which presents a shock hazard.
|
AC/DC radios (and transformerless televisions) were made with hot chassis, one side of the line connected directly to the chassis (with some radios, such as Arvin's model 540T, in metal cabinets), for decades. The problem with a hot-chassis TV or radio is that the chassis will be "hot" with the full line voltage if the line plug is inserted into the wall socket one way, but will be "cold" (at ground potential) with the plug reversed. This assumes that the outlet you are using is wired correctly; some are not. It is always best to be absolutely sure of the polarity of the AC socket before simply assuming it was wired properly when the house was constructed. This is especially important if you decide to replace the original cord and line plug with a polarized one; if the AC wall socket is wired backwards, with the "hot" slot now ground and vice-versa, there can be real problems (such as a shock hazard or damage to the device plugged into the outlet) if the house fuse doesn't blow first -- as it should.
Radios and TVs with hot chassis in metal cabinets can be death traps if the house fuse does not blow in case of a short to ground. I once read of someone who was using an AC/DC radio in his bathroom, and accidentally contacted the hot metal cabinet while adjusting the volume or changing radio stations. The house fuse blew immediately, saving the person's life. Another, less fortunate case was that of a mother who was bathing her baby in the kitchen sink, with a plugged-in electric toaster nearby. The baby's arms got caught up in the toaster's AC cord, and the appliance promptly fell into the water. The house fuse, for whatever reason, did not blow when the toaster hit the water; however, the child was instantly killed.