Safety Page

If you are working with electricity and your work area has a concrete floor, a rubber mat is essential, particularly during damp weather.

Where possible try to arrange a neat working area away from water or central heating pipes.

For safety try to arrange that this area is separate from the area occupied by your family. This is emphasised because inadvertently rushing to answer a telephone you might just leave a TV chassis connected to a supply and curious little fingers know nothing of the dangers of electricity.

Use an isolation transformer

Anybody who employs staff to repair domestic electrical goods is obliged to provide isolating transformers for their use.

They are not expensive, and if they are good enough for employees, they must be equally good for equipping the home enthusiast's test bench. Only a fool would set a lower price upon life.

If you can't isolate

In field servicing this item is frequently considered inconvenient and engineers frequently service live equipment which is not isolated from the supply.

The best advice is to keep one hand behind your back at all times you are working on powered equipment. If you need two hands, they say, you should find another way. It may be hard to comply but you should try.

Also learn where the anode and screen pins are on the more common valve types (e.g. pins 3 and 4 on many octals) and be careful around them. Keep your fingers off any terminal inside the equipment.

Use good test leads and you won't ever need to touch anything inside (except possibly a control grid connection to see if it causes a hum – not the best technique but frequently used).

Don't plug it in

Whenever you acquire a new treasure there's always a terrific temptation to try it out. With mains-driven equipment that means plugging it in and seeing if it works.

Well don't, not until you have made some quick checks. Is the mains cable (line cord) complete? It may have frayed or brittle insulation, allowing two wires to touch (or giving you a shock). An input filter capacitor (if fitted) may have broken down and could give a dead short. Electrolytic capacitors in the power supply may not be able to stand the surge of full voltage after many years of lying dormant.

Plugging in elderly appliances without making first-line checks is asking for trouble.

Older isn't necessarily safer

Many people who mistakenly feel that 'old technology' is somehow more user-friendly, in some strange way automatically good - merely because it is old. This is not the case. Approach old equipment with an open and alert mind and realise that a hot chassis, or a resistor line cord, or asbestos insulation, or selenium rectifiers require much more thought and consideration for safety. Remember, too, that the old-timers who talk so glibly about safety received an on-the-job training, having worked man and boy in the business.

We enthusiasts are mainly part-timers or newcomers to the hobby and haven't had the benefit of that training. And just because it's a hobby, that doesn't exempt us from safety drill. Live chassis are indiscriminate in whom they kill and even if you are a thoughtful, careful kind of person, that doesn’t mean the last person who handled the set was. Never drop your guard – you may know why wax was melted over grub-screws but another clown may not have done. He lost the proper grub-screws and used normal bolts… and the next person who grasped the on-off/volume knob of the radio wondered why it always gave a tingle!

Does this sound tedious? It shouldn't be so, because safety is never boring.

Charged capacitors

You can discharge capacitors to earth with a screwdriver or a wire but the preferred method is to use a resistor built into a grounding lead with a test lead end on it. A 10K resistor works fine to reduce or eliminate the spark. Just be sure to hold it on for a second or three.

And yes, it was a favourite trick in old-time television workshops to toss a charged electrolytic to a colleague with the word "Catch!". It's a nasty trick because one's natural reaction is to obey.

The live chassis

A large number of radio and TV receivers were produced using the 'universal' or 'AC/DC' technique which permitted the omission of large, expensive mains transformers. When switched on these sets employed a chassis common to one side of the mains supply. Incorrect polarity of the mains input connection usually had little effect with AC mains operation but could result in the chassis being LIVE!

The shafts of switches and potentiometers fixed to a "live" chassis may well be at chassis potential and thus live. The bakelite or wood cabinet is insulated but these shafts are not, and if someone lost the proper grub screw and replaced a knob using a cheesehead screw, the next person to grip that knob may get a dose of 230 volts. Originally these grub screws were sealed and embedded in wax but you cannot rely on subsequent tinkerers having the same high standards.


Many radios of the 1930's and 1940's incorporated small asbestos sheets to provide heat shielding. These asbestos sheets were generally attached to structures near the hottest valves, which were generally rectifiers or output valves.

It is essential to wear the correct protective equipment when working with asbestos. Ordinary dust masks are not effective. Protection requires a filter respirator fitted with a class P1 or P2 filter cartridge.

Any clothing must also be protected from contamination, and you should not use compressed air to blow away dust if asbestos is present.

Cathode Ray Tubes

Picture tubes are perhaps one of the most hazardous items in any valve TV receiver. This is because most are of glass construction and contain a very high vacuum. Before starting to remove a tube, first discharge the final anode connection to the chassis metalwork and preferably connect a shorting lead to this connection whilst you are working.

You may find that the deflection coils have become stuck to the neck. It is extremely dangerous to use a screwdriver prise them away. Gently heating with a hairdryer or soaking in methylated spirit is safer.

Disposal of picture tubes also requires care. Unless rendered safe they should never be placed in dustbins or skips.