Safety notes

Handling of old domestic radios and old TV sets means certain hazards. Only experts should open radios or TV sets and work on them while they are live.

I am not unrealistic and that's why I know that quite a number of hobby electronicists also work on their sets to repair them. Because of this fact the following notes.

Be aware that electrical equipment may hurt you. Read these notes before you try to repair. Nevertheless only you will be responsible for your activities. Repair only sets when you understand their operation.

Only replace components when you understand their function. You are uncertain? O.k. Keep your hands away from an opened set. And please read the final words for beginners and old hand alike at the end.

When you are not familiar with measuring voltages, currents and resistances, it is anyway pointless to try to repair, except perhaps to exchange a blown fuse or to replace tubes.

Now the notes:

• Before beginning restauration or repair work when possible always disconnect your set from the elec- tricity. Consider:
  
  Power supplies can store for a long time high voltages after switching off. TV sets can store for hours and even days high voltages in the picture tube (CRT).
  
  Discharge power supply capacitors with a 30 kilo- ohms resistor (about 45 seconds) before you start work on the set.
  
  
• By all means install a ground fault interruptor in the current supply of your work bench. Use as well an isolation transformer. (Radio and TV repair shops always work with an isolation transformer in the power line of the sets to repair. That way the galvanic connection to the power outlet is interrupted).
  
  
• When you have to repair a set with the power on (e.g. when doing measurements) don't touch with either the hands nor your head live components. The electric shock can hurt you or even kill you! When you have to do measurements while the set is on:
  
  In radio sets voltages of up to 300 volts may be present. Already voltages of 60 volts plus can be dangerous when going through the body. In TV sets there are up to 30 000 volts in the high voltage section and at the picture tube. In the line ouput stage and at the line transformer are also voltages of a couple of a thousand volts.
  
  Use only one hand with the measurement probe at or in the set. Keep the other hand in your pants pocket and with your head you will not touch any metal part of the set. That way you avoid getting into the electric circuit. Too much caution?
  
  No, just being clever. Your place of work should not be near grounded parts like central heating, water pipes, TV antennas or cable TV connection.The floor should be of the high insulating type.Never work barefoot!
  
  
• Especially ac/dc sets can be very dangerous! They were built until 1963.With these sets there is a galvanic connection of the 230 volts power line to the chassis! When the plug is inserted the 'wrong' way round in the power receptacle, there are 230 volts on the chassis opposite the earth tag of the receptacle!!! There is danger lurking! There also is danger when you either touch the antenna or earth (ground) and even when the set is closed avoid touching any external metalwork!
  
  Even the grub screws of the knobs should be well recessed so that you can't touch them accidentally! Never connect the earth (ground) wire directly to the chassis of an ac/dc set. Always use the earth (ground) jack via the existing capacitor. On no account keep in one hand the earth (ground) plug while your other hand touches the chassis. Logically this is valid also for TV sets, which at that time were exclusively ac/dc sets.
  
  
• Dc sets. Never connect a dc set to the ac line!
  
  
• TV sets. The picture tube holds as well to electrical hazards also mechanical ones. Inside the picture tube is an almost complete vacuum, which creates a high pressure on the outside of the tube.Especially the neck of the tube is sensitive to blows and pressure. In case of damage the result is an implosion with full force like an explosion. Splinters of glass may fly like bullets across the room.
  
  
• Old radios and TV sets may become quite warm.
  
  
• Don't leave the radio or TV set during repair unattended! Keep the set away from inflammable material!
  
  
• When you leave the bench, switch everything off, remove open power line cords. Children or other members of the family could touch the equipment or the hot soldering iron while you are away. When the cabinet of the TV set is left open, safeguard the room against entry when you are absent.