WARNING: HIGH VOLTAGE. SHOCK and FIRE hazards. Vacuum tube / valve electronics runs on much higher voltages than transistor or solid state devices. These sets were generally not provided with interlocks or power fuses. In certain designs, the power line may be connected directly to the chassis. Many home-entertainment electronic devices had 250 volts or higher as a standard operating voltages, and voltages as high as 750 or 800 volts, may be present in some circuits.
Fault conditions may cause HIGH VOLTAGE to be present ANYWHERE, even after the set it turned off and disconnected from the power line (mains). Use a grounding lead to assure that no voltage is present before working on a set. Be especially careful to ensure that 'reservoir' capacitors and the high-voltage line in general is discharged before touching anything in the set.
Be especially careful with old television sets; these used even
higher voltages, and the picture tube requires several kilovolts as a minimum:
the tubes' glass surface is often coated inside and outside to form a *very*
good capacitor, so NEVER go and touch a tube without first ensuring, with a
well-insulated shorting tool, that all this energy is discharged.
Such a tool can be fabricated from a well-insulated screwdriver (rated for at least 10KV and kept clean) with a good wire bond to the blade, the other end of the wire ending in an alligator clip which is FIRST connected to the chassis or the grounding of the tube. The screwdriver tip is then carefully pressed into the anode connector at the side of the tube, such that you can see that there is contact. Move it around a little to make sure the contact has been made, and then remove the screwdriver. Remember, if you get a shock from the tube, it might make you jerk in any which way, possibly dropping the set or the tube, and there is then the additional danger of injury from the imploding glass tube if it breaks.
There is sufficient power in old radio and T.V. sets to overheat components to the point that they will catch fire, and many components used in old electronics will support combustion. While addition of a fuse can reduce fire hazards, it is not a sure and complete protection against overloads which may be adequate to overheat components, but inadequate to blow the fuse. In addition, some soldering irons operate at temperatures of 400-500C (approx 700-900F), and are hot enough to ignite many flammable materials such as paper and cloth. Conventional modern soldering, in contrast, is often performed at some 300 - 320C, and the joints are smaller with much less cooling time and with far fewer combustible components.
You should have an appropriate fire extinguisher in your workshop or wherever you work on your sets.
Several of the CHEMICALS and PROCESSES discussed in the newsgroup, and in the FAQ, present safety hazards of one type or another. Fire hazards are common, and many chemicals and processes require substantial ventilation as well. Read manufacturers' labels and follow all instructions for safe handling closely. Above all, do not store or use chemicals with food or food preparation items and do not store such items in fizzy-drink bottles etc.
Small children (and some not so small)---if you have some of these around, take some precautions to make sure their inquisitiveness does not get them into something that will hurt them, or damage anything. Old electronic equipment is full of bright colors that will attract small fingers. The best thing to do with children is introduce them to radio. Don't just tell them "no, don't touch," etc. It's amazing how quickly, diligently, and thoroughly a child will learn mathematics and physics, with the help of an old radio and someone who will take the time to explain it to them. However remember noxious chemicals and children don't mix.
Do not attempt any process unless you know exactly what you are doing, have evaluated the risks, and have taken safety precautions. Many of the regular contributors to rec.antiques.radio+phono have been formally trained in chemistry and physics laboratory procedures, and use chemicals and processes professionally. They may discuss techniques that require substantial safety precautions without noting the hazards involved, assuming others will already know the risks.
If there is the slightest doubt in your mind about the safety of any process or material, don't charge off and "just do it" because others say "it works." Ask questions. There is no substitute for learning under supervision. Many community colleges and high schools offer courses open to adults, including courses in laboratory sciences and shop practices.
You can E-mail the author of these pages (Trevor Gale) by using this link. on the Dutch Internet service provider XS4ALL.