A focusing screen provides a flat surface on which an image can be precisely focused and allows the eye to see the whole image at once for framing and composing. It normally comprises a ground glass screen, a fresnel lens and one or more focusing aids.
A ground glass screen scatters light in all directions allowing the whole image to be seen, but the picture you see is brighter in the centre. Coarse etching of the glass reduces this. A fresnel lens comprises a series of stepped, concentric rings. Read the rest of this entry »
Yes, you too can be the proud owner of a home-entertainment system and it doesn’t have to cost you a small fortune. If you have ever wondered how your mates get to have sound booming from seemingly every corner of the house when merely watching TV, we have the answer (naturally!). All you need to do is connect your TV to your video machine to your Hi-fi (these don’t have to be top of the range) after having acquired a couple of cables to make all the connecting possible.
You WILL NEED
(This will vary depending on what it is that you are connecting to what.) Read the rest of this entry »
Downlighters are ceiling fittings of tubular shape alloy containing reflector bulbs or spotlights to produce pools of light on the table and floor against a dark ceiling background. They can be mounted as close- ceiling fittings but there are also versions for sinking flush with the ceiling and some are semi-recessed. The flush version, and to a lesser extent the semi-recessed version require a deep void above the ceiling.
These fittings are also mounted flush with the ceiling but instead of producing pools of light on the horizontal plane, produce them on walls as part of a lighting scheme. Colour lamps and coloured walls produce the required effect. Read the rest of this entry »
Most labour-saving household appliances contain an electric motor of some description. They are the workhorse of these appliances and most of them are capable of coping with the work loads inflicted upon them. However, some motors, either through poor design or as a result of manufacturers’ cost limitations, are inadequate for the job they are required to do. Adequate or not, at some point it is almost inevitable that they will fail or simply wear out. To delay this, use the appliance with some care and attention, be aware of its limitations and carry out regular inspection and servicing. This will prevent small problems escalating into major ones
Not only do the sizes of motors vary greatly between products, so too do the ways in which they work. To diagnose faults successfully and service or repair appliances, a working knowledge of motors is essential. The following provide a basic introduction to the various types, a description of how they work, the appliances in which each may be found and their particular advantages and drawbacks. Specific problems can be found on individual appliances. Read the rest of this entry »
These are among the most frequently used items in the home. Generally, they are very reliable, but when a problem does occur, it is usually at the most inconvenient time. Over the years, ovens and hobs have become increasingly complex with the addition of digital timers, touch controls and other refinements.
It is essential to remember that these appliances are connected directly to the mains supply and, as with any repair, cleaning or service, must be completely isolated. In this instance, the main double-pole isolation switch for the appliance must be switched off and also the fuse for the cooker/hob circuit removed from the main distribution board. If an MCB is fitted in place of a fuse, ensure it is in the off position. Do not proceed with any repair or service if both these requirements are not met and also make sure you advise others who may use the switch of your intentions. Read the rest of this entry »
Throughout this post, references are made to meters and their use in continuity testing of individual parts of the appliances and their connecting wires. All testing and checking for ‘open’ (not allowing for current flow) or `closed’ circuit (allowing current to flow) must be carried out using a battery-powered multimeter or test meter. Testing should never be carried out on live items under any circumstances. Appliances must be disconnected from the mains supply. Read the rest of this entry »
The toaster is another appliance that uses heating elements and, in most instances, a bi-metal strip thermostat to control the length of time the bread is exposed to them. This, in turn, relates to the degree of browning required by varying the position of the bi-metal contact points. When bread is inserted, a latched spring system is actuated to hold the bread carrier in place. At the same time, it makes a switch contact to supply power to the elements. The heat from the elements toasts the bread and also heats the bi-metal strip, causing it to bend. Read the rest of this entry »
There are no faults with CD players that are within the capabilities of the D-I-Y repairer. Do not attempt adjustment or servicing to any internal components; leave it to a trained service engineer. However, looking after your equipment properly minimizes the possibility of faults occurring.
The first consideration is the positioning and environment of the player. Do not place a CD unit in strong sunlight, near heat or in damp or humid conditions. The CD system requires very close tolerances to be maintained for accurate disc reading and sound reproduction. Read the rest of this entry »
The brush roll is supported on bearings at each end so the barrel rotates freely. Types of bearings, barrels and brushes differ from model to model as well as between manufacturers. Some manufacturers supply individual parts for the brush roll, such as brush strips, bearings and barrel; others supply only complete assemblies. The brush roll on some models may have removable brush strips, whereas others may be a solid brush roll of wood or plastic with fixed brushes. A small selection is shown here to highlight the differences. Read the rest of this entry »
Cord rewinds are now found on all types of cleaners, from simple hand-operated versions to the fully automatic rewind at the touch of a button. Many auto cord rewind systems use open coil springs and great care should be exercised if a stripdown of these systems is called for. Protection for the eyes is recommended. Goggles afford adequate protection from the spring itself or any item that it may throw out in the event of its slipping from position.
Operation of the cord rewind relies on tensioning of the rewind spring as the cord is pulled out for use. A small brake pad prevents the immediate return of the spring and cord drum to its original position. Read the rest of this entry »
