Formerly imperial ratings were used for fuses and circuit breakers, but the international Renard ratings have now been added and will supersede them.
Fuse manufacturers are still using the imperial sizes while circuit breaker manufacturers have mostly changed to the new ratings. An equivalence chart is shown above.
The miniature circuit breaker (MCB) is now widely used and overcomes all the problems associated with ordinary fuses. It is a small, sophisticated unit affording a much higher level of protection than an ordinary fuse. It is tamper-proof and the unit involved is easily identified when one has tripped (the switch moves to the ‘off’ position). Most importantly, MCBs cannot be reset if the fault still exists; this eliminates the foolish and highly dangerous practice of putting in the wrong fuse wire or cartridge just to get things ‘conveniently’ working again for the time being. Read the rest of this entry »
A basic understanding of electricity is essential, even for those who do not intend to carry out any repairs or servicing of appliances. Ignorance is no protection against your own or someone else’s errors and oversights, whether with repairs, servicing or installation.
Power is supplied to an electricity substation at a very high voltage — 400,000 volts — in three-phase form. There it is converted, via a transformer, to 230 volt single-phase for distribution to our homes. In normal circumstances, current flows from the live supply of the substation’s transformer, through the electrical appliances used in the house and back via the neutral conductor (cable) to the substation transformer’s neutral pole (a closed loop). Read the rest of this entry »
To test for an open circuit in a component, make a note of and then remove the original wiring to that component. If this is not done, false readings may be given from other items that may be in circuit. Attach the ends of the two probes of the meter to the suspect component. For example, to test a heater for continuity, place the probes on the tags at the end of the heater and watch the meter. The needle should move. At this stage, it does not matter if the needle does not reach zero. If the heater is open circuit (no movement), it should be tested further. If closed circuit, the heater has not failed. Read the rest of this entry »
The electric iron used to be a simple appliance consisting of an electrical heating element pressed on to the sole plate of the iron and controlled by a simple variable bi-metal thermostat. Its rugged construction and lack of gadgetry made it a long-lasting appliance. Irons have changed greatly in recent years, with attention to styling and reduction in weight making them much more attractive and easier to use. In addition, many irons now have a variable steam facility, a steam release valve and a plain cold water spray. Read the rest of this entry »
Whether cheap and simple or astronomically expensive, all decks are averse to dirt and debris which is statically attracted to the vinyl record. It then damages the stylus resulting in the all-too-familiar click, pop and jumping of the track.
Sound is stored on a vinyl record on a continuous groove starting at the outer edge and finishing at the centre of the disc. The groove has microscopic ridges proportional in size to the sound wave that created them. When the record rotates, the stylus is deflected by these ridges as it runs in the groove. These minute deflections are then amplified. Two requirements must be met for the stylus to track correctly. The first is that the groove of the record is free from all blemishes and foreign matter to which the stylus would react. The other is that the arm holding the stylus must apply just enough weight to hold the point within the groove (usually 1-2 grams) but not so much as to create excessive wearing of the groove. Read the rest of this entry »
Most households have at least one item of video and audio equipment: television, video, sound system, CD player and so on. As a rule, it is not wise for the amateur to attempt to repair such high tech equipment, as this requires expert knowledge, expensive equipment and detailed service manuals. The intricate nature of internal mechanical and electronic components and the high voltages make it inadvisable to remove panels or outer covers. It is more sensible to leave this to the skills of the trained specialist. Read the rest of this entry »
Low insulation is best described as a slight leak to earth of electricity from the wiring of one or more of the components or wiring in an earthed appliance. If very slight, it will not harm the appliance but is an indication of faults to come and should be corrected immediately for safety reasons. The condition occurs during the progressive breakdown of the insulating properties of a normally electrically leak-proof system.
It may be caused by normal wear and tear over a long period, resulting in a breakdown of the insulating coating on wiring, motor windings, heater elements, etc. Such a breakdown of insulation may not result in a failure of this part at this stage and the appliance may still function as normal. This, however, is not an excuse to ignore low insulation; failure to trace and rectify it is foolhardy because it compromises safety. Also extra expense is likely to be incurred in the long run. Read the rest of this entry »
