HSE Schmidt Elektronik www.hse-radio.de

Tube Radios, Record Players, Tape Recorders, Tefifon, Television Sets

Electrical safety for old electrical devices

Dear radio friend,

for line-operated devices, cables and metal parts that are connected to the mains must be insulated against any human contact. There are two different
construction types: 

  1. Inside devices without mains separation all metal parts are connected to the mains voltage. The cabinet, keys, rear panel and knobs form the insulation. For these devices it is very important that they must never be operated without cabinet, knobs, keys or rear panel. Also protruding screws are life-threatening. Commonly capacitors build the insulation for the antenna AND the earth connectors. The function of these capacitors must be checked regularly (see below). Connecting of accessory units like second speakers, record players or CD players etc. is NOT recommended for this construction type. There are also corresponding capacitors that form the insulation for those accessories. Some of these device types even do not have insulation at all for the input and output connectors; in those cases one can often find the notice on the rear panel: "nur für Geräte nach VDE" (only for accessories according to VDE). Therefore loudspeakers, record players etc. must be fully insulated and are at mains voltage.
  2. Devices with main insulation have a safety transformer after the mains switch that insulates the following circuitry and the chassis from the mains voltage. Therefore sockets and metal parts are non-hazardous for human contact. Thus accessory units can be connected. However it happens often that faulty capacitors, brittle cable insulations or faulty transformers prevent proper mains insulation.

Have your radio, tape recorder or any other device checked from a technician. Every electric handicraft business should have an appropriate testing device.

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