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In Reply to: Re: "Shocking" Scott 312C Tuner posted by Ron Oehlert on March 5, 2007 at 14:28:07:
The original purpose was to get the chassis to ground potential at high frequencies in an era when grounded outlets were rare. A small value cap would usually be connected betw one side of the line and chassis, sometimes with a resistor in series. If the cord was plugged in the "right" way, the chassis would be connected to neutral thru the cap. If it was plugged in the wrong way, the chassis would be connected to the hot side of the line thru the cap. When connected this way under intended conditions, the cap would limit current to a safe level if for some reason there was a circuit betw the chassis and ground...such as thru a grounded person. Most persons would experience such a condition as a little tingle. Real problems arise if the cap is leaky or fails outright since the chassis can become totally hot. Thus the term "death" which is a bit of hyperbole IMO but the point is valid.
Since modern home wiring always includes a ground, the best approach to this cap is to remove it and attach a grounded cord set and properly ground the chassis. However, if one believes in total authenticity of vintage circuits (as some do around here), there are caps made specifically for this purpose. These caps have defined failure modes and carry the proper approvals of testing agencies like UL. Check out archives under moniker of "SGMLAW" for the gory details of cap designations and where to find them if you choose this route.
Ahh, I get it now. Interesting that in the day when outlets were not grounded that they weren't polarized (hot is small hole, neutral is large hole) and plugs were not polaraized.
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