An Effective Insulator

Radio Record, Volume III, Issue 17, 8 November 1929, Page 28

An Effective Insulator

For Preventing Short. Circuits THE risk of short-circuiting is con- ~ giderable in a set which employs sereened coils, or which has the shields or cores of the transformers earthed, This is due to the large areas of exposed metal which are connected to the A battery supply, and which may be connected accidentally to a B battery positive lead. Though contact may be only momentary, yet the high’ voltage thus applied would probably burn out the valve filaments. . The risk of short circuits can be greatly reduced by covering such exposed metal surfaces with an insulating layer. A simple and effective method of doing this is to apply two coats of quick-drying stove enamel or shellac varnish to these surfaces. In the case of earthed transformers it is also necessary to paint the heads of the baseboard screws if these pass through metal lugs in electrical contact with the frame or the shield. This method of providing insulation is an exceedingly useful one for other purposes as well, Bare leads, for example, can be protected in this way after the wiring of the receiver has been completed. Soldered connections to tags can be insulated in the same way. Precautions should be taken, however, to prevent the enamel or shellac from running under terminals or over ebonite insulation. RN aR CTS EERO