Televisi

E-Pendidikan dimaksudkan untuk merangkum informasi yang berhubungan dengan menggunakan Teknologi Pendidikan untuk membantu Pendidik, Pelajar dan Masyarakat
E-Pendidikan.Com
Komputer & PendidikanInternet & PendidikanTeknologi & PendidikanLaboratorium BahasaWebsite & PendidkanTV & RadioHOME
Preventative Maintenance (PM)
Indonesian Context

INDEX

The Importance of a Preventative Maintenance System

One of the key issues that generally reflects the reliability, utilisation, and ultimately the quality of any technical facility is the system that is in place for the provision of pro-active and re-active maintenance. A true preventative maintenance (PM) system embraces both pro-active and re-active maintenance procedures. By responding to data collected from the re-active maintenance we are able to better define the needs of the pro-active procedures. Therefore, a true preventative maintenance system is one that is forever-developing (growing). A well designed preventative maintenance system is also a very useful means of providing staff orientation and training for new staff.

Whenever maintenance issues are discussed cost is usually the first issue to be raised. However, the cost of preventative maintenance is relatively moderate compared to the cost of repairing the more serious damage which can occur – or the total replacement of items, which is often necessary if we do nothing. The second issue, is the cost of the equipment necessary to carry out the maintenance. The most important items of "equipment" for implementing an effective preventative maintenance system are our eyes, our nose, our ears, our experience, and our judgement, which are all free. Consistent with my understanding of Indonesian secondary school budget limitations, all procedures that are recommended in any of my facility quality improvement programs have been designed to address the more practical low-tech/ low-cost options and approaches.

We often encounter problems in Indonesian science and language laboratories that are not related to the facilities themselves (water damage - leaking roofs, timber damage – white ants, and cable damage – rats). Routine inspections together with some minor action can prevent more serious or disastrous outcomes (ie. minor repairs, chemical treatments, and pesticides). These issues may be perceived as being outside the actual duties of the language laboratory technician, however, technicians must assume responsibility for addressing and where possible resolving these problems. The technician must schedule regular building and safety inspections by the appropriate personnel into their preventative maintenance program.

If spare parts, or the funds for spare parts are not available to carry out a repair or replacement immediately look for options that at least prevent any further deterioration or danger. Spare parts are certainly one of the most important considerations when designing a preventative maintenance system. Ideally spare parts should be budgeted for in the initial purchase of the equipment. It may be necessary to reduce the initial purchase cost of the equipment by looking at other options (brands, models, etc.) in order to make funds available for the purchase of adequate spare parts. It is preferable to have a lower technology facility that can be maintained for ten years rather than the latest technology which will only be operative until the first technical failure.

Sections 1 - 5 of the language laboratory PM Guidelines below relate specifically to language laboratories, however, I believe that the principles can be adapted to address preventive maintenance planning for all school facilities including science and computer laboratories. They are basically founded upon systematic checking and repair in order to prevent more serious damage or interuption of teaching programs. The key aspect of any school preventive maintenence system is that it contains routines that as best as possible assure the readiness of facilities for teachers and learners. Points 6 - 9 should be useful to all technicians


Language Laboratory
Preventative Maintenance

1. PREVENTATIVE MAINTENANCE DAILY INSPECTIONS - PROCEDURES

Procedure

The first step of any preventative maintenance system is to use your powers of observation. The most important items of "equipment" for implementing an effective preventative maintenance system are our eyes, nose, ears, experience, and judgement.

1. Routinely walk around the language laboratory at regular intervals (once or twice a day if possible). Look for damaged or unplugged headsets, physical damage to the master console or student units, student units with missing tapes, frayed, loose, or damaged cables, damaged furniture (especially chairs), etc. * As you carry out the inspection tidy up cables and headsets so that they are neat.

NOTE: If students see that equipment is respected and cared for by staff they are more likely to treat the equipment with respect.

  • Check the master console (see Master Console section)
  • Turn on the power to the stabilizer and main power supply
  • Listen as the system "powers up" for any unusual sounds.
  • NOTE: Always give attention to any unusual sounds or odors coming from any of the electrical equipment. These may give an early warning of any cable damage or faults in the system.

    If you suspect any faults in the system turn everything off immediately. A delay may result in more serious damage to other equipment.

    1. Inspect all cables and connections, especially where the cables go into, and come out of the floor ducts (or conduits).
    2. Also look for insects or rodents (rats) which may have come into contact with the live cables or terminals. As their bodies decay they can cause a short circuit which can cause a circuit breaker to open, or more serious damage.

    Disconnect the power before attempting to remove anything in contact with the power supply!

    If a fault is not easily identifiable from a physical inspection disconnect the stabilizer from the main console and check it without anything else connected.

    Variacs and stabilizers should be kept well away from the master console because magnetic fields can cause audible hum. Single insulated wires and open terminals (see picture) should not be accessible (provide safety covers).

    Disconnect (unplug) the stabilizer from the power before doing any other ‘disconnecting or connecting’.

    Due to the high temperatures, dust, and humidity in Indonesia, faults in stabilizers are quite common.

    Because of the high levels of protection provided in commercial language laboratory circuitry the fault is most likely to be in the electrical connections/ plugs/ sockets, wiring, or the stabilizer. An overload in the main console will usually cause the laboratory to shut down.

    2(a). GENERAL PERFORMANCE CHECKS (Daily)

    Audio Active (AA) Laboratories

    Procedure

    With the language laboratory master console turned-on:

    1. play a test tape in the master recorder and switch the sound so that it is being transferred to the student units (see operation manual for your particular laboratory)
    2. check the quality of sound coming from the master recorder
    3. go to each student unit and put on the headphones and listen carefully to the quality of the sound in both ear-pieces (check that the student volume is turned up). Rub your fingernail against the microphone. You should be able to hear the scratching sound clearly in both ear-pieces
    4. with the headphones still on, gently wriggle the cables, especially close to the plug and each ear-piece. If there is any crackling, or if the sound disappears you can usually repair the fault by cutting the cable near the break and re-terminating the cable (see soldering).

    2(b). GENERAL PERFORMANCE CHECKS (Daily)

    Audio Active Comparative (AAC) Laboratories

    Procedure

    1. rewind all the student cassette recorders
    2. insert a test cassette (cassette containing some quality speech or music) into a master recorder and check the quality of sound by playing the tape. If the sound quality is poor clean the master recorder heads (see head cleaning) and try again. If the sound quality is still poor check the ‘head azimuth’ (see Head Alignment).
    3. NOTE: It is important that the master recorder sound quality is of the highest level possible because the quality of the student tape copies will only be as good as (or less than) the quality of the sound from the master player.

    4. transfer 10minutes of sound from the master (test) tape to the student recorders (see the operation manual for the particular type of laboratory you are using)
    5. when the transfer is completed rewind the student tapes and start them playing
    6. monitor the playback quality of each student recorder briefly using the individual monitor buttons on the teacher console
    7. NOTE: Check for level and clarity (quality) of the sound from the student recorders. Using this method it is easy to identify the general condition of the heads of the recorders in the entire laboratory. If more than two recorders need their heads cleaned – clean the heads in all the recorders including the master recorders (see head cleaning) and make a record of the date in your maintenance log (this information will help schedule future head cleaning).

    8. go to each student unit and put on the headphones. Test the operation of the main student unit controls (FF/REW/PLAY)
    9. press the tape play button and listen carefully to the quality of the sound in both ear-pieces. Gently rub your fingernail against the microphone. You should be able to hear the scratching sound clearly in both ear-pieces (check that the student volume is turned up)
    10. with the headphones still on, gently wriggle the cables, especially close to the plug and each ear-piece. If there is any crackling, or if the sound disappears you can usually repair the fault by cutting the cable near the break and re-terminating the cable (see soldering).
    11. rewind all student recorders so that they are ready for use by the next teacher

    3. STUDENT AND MASTER RECORDERS

    Head Cleaning (Weekly)

    AAC Laboratories – All master and student units

    AA Laboratories – Master units only


    The audio heads on a cassette recorder have a vertical gap across which a changing magnetic field imprints a magnetic sound track upon the cassette tape. It is most important that this gap is kept clean and free from a build-up of the magnetic oxide from the cassette tape and also dust from the environment. If this gap becomes ‘dirty’ the general quality of the sound deteriorates and may be of a low level and not very clear.

    There are two main heads on cassette recorders, the record/ playback head, and the erase head. However, when we are cleaning the heads all of the parts of the cassette recorder that come into contact with the tape also need to be cleaned. These include the capstan, pinch roller, and any tape guides (see diagram *).

    Using a cotton bud and alcohol or head cleaning fluid (Head cleaning kits are also available):

    1. turn on the master console
    2. open the door to the cassette compartment
    3. moisten the cotton bud with alcohol or head cleaning fluid (not too wet) and wipe the surfaces of the heads thoroughly, finishing with vertical up and down movements to make sure the head gap is clean.
    4. to clean the capstan press the play, then the pause button to get the capstan rotating. Clean the rotating capstan by holding a moistened cotton bud against it. If the cotton on the cotton bud twists around the capstan turn off the cassette player and the cotton should slide up off the capstan.
    5. to clean the pinch roller release the pause button and the roller will rotate. Hold the moistened cotton bud against the roller, moving it up and down to remove all the oxide and dust.

    NOTE:

    1. It is especially important to clean the pinch roller and capstan thoroughly because a build-up of oxide or dust on them can make them "sticky". If they become sticky the tape can adhere to them and can cause a major tape-jam seriously damaging the tape.
    2. After cleaning the pinch roller also inspect its surface and make sure that it is flat and even (no signs of permanent wear or deterioration). If there are signs of significant wear order (or acquire locally) suitable replacements immediately and schedule a replacement date. Delays may result in serious tape damage or erratic performance.

    1. clean all other surfaces that come into contact with the tape ie. tape guides
    2. allow sufficient time for the cleaned surfaces to dry before using the equipment.

    Head Demagnetization


    The cassette recorder covers have only been removed from the cassette recorder to assist visibility for the photographs.

    In the photo the demagnetizer is demagnetizing the erase head (top right).

    Head demagnetizing is usually recommended to improve sound quality and the frequency response capability of the audio heads which may have become partially magnetized. However, probably the main reason for periodic head and tape-path demagnetization is more of a preventative procedure to avoid the possibility of partial erasure of the master or student tapes. Partial erasure can occur when pre-recorded tapes pass by magnetized objects. Demagnetizing removes the residual magnetism that can build up on the tape heads, guideposts and other parts in the tape path. Small hand held head demagnetizers are available from some local audio and electronics shops (alternatively - from Glodok in Jakarta).

    Procedure

    1. switch off the cassette recorder and pull the plug out of the power socket
    2. plug the head demagnetizer into the power but do not switch it on until you are ready to use it
    3. check that the soft plastic (anti-scratch) cover is in place on the head-demagnetizer tool
    4. open the cassette compartment door (on some cassette recorders the door is removable and this can make access easier)
    5. hold the demagnetizer at a distance of about 600mm from the recorder and turn it on. Slowly move it towards the recorder and place the tip against (in contact with) the heads, capstan, and guides - rotating it slowly against their metal surfaces.
    6. when you have finished slowly take the demagnetizer back a distance of at least 600mm from the recorder before switching it off (otherwise there is a possibility of leaving some residual magnetism on the heads when the demagnetizer is turned off).

    Head Alignment

    AAC Laboratories – All master and student units

    AA Laboratories – Master units only


    As mentioned in the Head Cleaning section, the audio heads have a vertical gap in their magnetic circuit. For quality reproduction it is also very important that this gap is at right-angles to the direction of the tape movement. If the head is not correctly aligned the first thing that you will notice is that the high frequency sounds are low in level or can not be heard at all. The audio will not be crisp and clear.

    This alignment is called "Azimuth Alignment" and is another basic performance check which should be conducted at regular intervals - at least twice each year. The alignment should only require about one minute per tape machine. For a 24 position AAC language laboratory (including the master recorders) it shouldn’t take any longer than approximately 30 minutes.

    To align the azimuth of the tape machines you will require a "test tape". Special test tapes are available commercially, however, they are expensive. You can do a reasonable azimuth alignment using a quality commercially produced music tape by adjusting the azimuth to achieve the clearest high frequency reproduction. You can also make a simple (but adequate) test tape using a new cassette recorder and an audio signal generator. A suitable audio signal generator should be available from the science (IPA) laboratory in your school (see: Making a simple azimuth test tape).

    Azimuth Alignment (Procedure)


    Again, the cassette recorder's case has been removed only to improve visibility of the heads for the photographs. When you do this adjustment the recorder will actually contain a cassette and be in the play mode.

    1.One side of the Record/ Playback Head is supported by a spring and screw arrangement (see the diagram). This screw allows adjustment of the head’s azimuth.

    2. De-magnetize the Record/ Playback heads (see Head Demagnetization)

    3. Insert the cassette tape that you are going to use into the recorder.

    4. Start the tape playing (press PLAY).

    5. Listen carefully to the sound being reproduced from the tape. Using a non-magnetic (de-magnetized) screwdriver (special alignment tools are available with plastic shafts) very slowly rotate the azimuth adjustment screw to the left and to the right selecting the position where the high frequencies are clearest and strongest.

    Note:

    Some cassette players have a special access hole above the azimuth adjustment screw (when the tape heads are in the play position) for this purpose. On the Tandberg System 500 recorders a small panel above the heads can be removed completely.

    Making a Simple Azimuth Test Tape

    1. Choose the most recently purchased cassette recorder available.
    2. Demagnetize the tape heads and tape path components (see Head Demagnetization).
    3. Insert a new (empty) cassette tape into the tape machine and fast forward it to the end and then rewind it to the beginning again.
    4. Connect an audio signal generator output to the input of the cassette recorder (Line Input, or Microphone Input socket).
    5. Set the cassette recorder in RECORD mode and press PAUSE.
    6. Turn the audio signal generator on and record (release the PAUSE button) 2 minutes of signal at 8,000 Hz. Check the quality of the recording by playing the tape. If the sound is distorted reduce the level of the sound (attenuate) from the signal generator and try again.
    7. Record 2 minutes of sound at 8,000 Hz, another 2 minutes at 10,000 Hz, and another 2 minutes at 12,000 Hz.
    8. On the other side of the tape record 30 minutes of signal at 12,000 Hz. This is the side that you will normally use for doing the Azimuth test.

    4. MASTER CONSOLE

    For master consoles (freely mounted on the teacher desk - as with the Tandberg System 500). Inspect the power cable and control cables for damage (nicks, cuts, fraying). Also check that the recorder is sitting securely on the bench in a safe position (cables not protruding, and not likely to fall if it is accidentally bumped).

    Turn-on the console (all console types) and check;

    1. all switches, buttons, and knobs for free movement and damage

    2. that the volume controls are not ‘ noisy’* when they are rotated

    3. that the tape mechanism operates smoothly

    4. the quality of the sound from the master recorder using a test tape

    Attempt to repair (immediately) any defects within the time available, or record the defect so that you can repair it later (or have it repaired by an outside technician).

    *‘Noisy’ volume controls can usually be serviced by spraying them with contact cleaner which is available from most electrical/ electronic stores (do not use a lubricant type spray – ie WD40). One of the most famous brands is "Servisol", however most of them are quite effective.

    5. HEADPHONES

    Clear reliable sound and student comfort are two very important factors which can significantly affect student motivation and concentration.

    Damaged headphones can be uncomfortable and dangerous. They should be repaired immediately, or removed from the language laboratory until they have been repaired.

    Procedure

    (Testing Headphones)

    With the language laboratory master console turned-on:

    1. carefully inspect the headphones for damage
    2. check that the student volume is turned up. Put the headphones on and rub your fingernail against the microphone. You should be able to hear the sound clearly in both ear-pieces
    3. with the headphones still on, gently wriggle the cables, especially close to the plug and each ear-pieces. If there is any crackling, or if the sound disappears you can usually repair the fault by cutting the cable near the break and re-terminating the cable (see soldering).
    4. clean the ear-piece cushions using a soft cloth dampened with a mild antiseptic solution.

    NOTE: Sometimes replacement parts can be manufactured locally. However, If you produce parts locally always check that there are no sharp edges or hazards for the students.

    One of the most common faults is a failure of the clamp which joins the head support to the ear-piece (see photos). If you do not have spare parts, or if there is going to be a long delay in the supply of the spare parts, you can take one of the good brackets (not the complete headset) to a local tradesperson (tukang besi). He will probably be able to make a new bracket at a relatively low cost. (It is recommended that you make several spares as it is usually more economical to make several, than individually as required).

    6. SOLDERING

    Equipment

    For soldering electronic circuits, and for carrying out the types of repairs that you will need to perform in a language laboratory the following equipment is recommended:

    • A 25 to 40 Watt soldering iron
    • Solder (resin core) 0.7 mm & 1.5mm
    • Solderwick - various sizes (for de-soldering)

    Heat the components and let the solder melt onto the joint

    Technique

    Good soldering requires cleanliness. This includes both the materials that you want to solder, and also cleanliness of your soldering iron itself. The main differences between general soldering as in plumbing, and the soldering of electronic circuits are:

    1. for electronic circuit soldering we use only resin cored solder (wire solder with resin flux inside it), we do not use corrosive fluxes such as bakers fluid
    2. when soldering electronic circuits the resin cored solder is applied to the heated surfaces that we wish to solder – not the soldering iron

    Step 1. Clean the surfaces of the wires, connectors, or circuit boards that you wish to solder.

    Step 2. "Tin" your soldering iron. Heat up your soldering iron to its normal operating temperature. Wipe the tip of your iron with a damp cloth or sponge to clean it. Apply some of the resin-cored solder to the tip of the iron (it should flow smoothly over the surface of the tip). Wipe off any excess solder and flux from the tip, it should now look clean and shiny and ready to use.

    Step 3. Place the tip of the soldering iron so that it makes contact with both of the surfaces that you wish to solder.

    Step 4. Apply the resin-cored solder to the surfaces that you wish to solder. If the surfaces are at the right temperature the flux will melt and flow out from the solder, and then the solder will melt and flow smoothly over the surfaces of the components making a good joint (not a "dry joint" – bad joint).

    NOTES:

    1. Do not apply too much solder to the joint, and do not move the components until the connection has cooled-off sufficiently (after removing the soldering iron).
    2. Always be careful when using soldering irons because they can cause serious burns, and unplug the iron when it is not being used.

    7. LUBRICATION - Electronic Equipment

    In modern electronic equipment, such as is found in language laboratories, it is generally not necessary to routinely add any oil, grease, or other lubricants. Moving parts are pre-lubricated at the factory and do not normally need any further lubrication during their lifetime. However, If you are certain that it is necessary, use lubricants sparingly!

    Over-lubrication can be worse than under-lubrication. Do not use any lubricants unless your inspection reveals a specific need. Sometimes you may find dry capstan bearings, motor shafts, levers, or gear shafts. If possible, disassemble and clean out the old lubricant before adding fresh oil or grease. A light machine oil (electric motor or sewing machine oil) can be used for gears, pivots, and idler wheel shafts, and also on plain bearings (not ball or roller bearings). Grease is used on sliding parts and gear teeth.

    In general, do not lubricate anything unless you are certain that it is necessary.

    8. RECORDING MAINTENANCE DATA

    The purpose of recording information about the maintenance and repairs performed to the laboratory is to enable you to:

    1. review and plan the probable spare parts needs for the next years budget
    2. keep other staff informed, so that they can easily find out what types of problems occur (assists management).
    3. to help develop an improved (growing) preventative maintenance system which will be based upon the past performance of your particular laboratory, because every installation is slightly different.


    This card must be filled in every time a repair is carried out on a piece of equipment (even if no spare parts are required). This record shows at a glance what types of problems have been associated with the equipment, how they were remedied, and what spare parts were required.

    Besides the obvious advantages for management and development of the PM system, this card is also an excellent starting point for new trainees. Training tasks can be assigned based upon authentic type faults.


    This second card is taking the PM system one step further. Each individual type (same make and model) of equipment has a card indicating weekly, monthly, and annual routine PM tasks which have to be performed. On the left you can see a card indicating the weekly checks required for a language laboratory master console. These cards are an adaptation of the Systematic Audio Visual Equipment Maintenance (SAVEM) system developed by the South Australian Education Department. The original cards have different colours for the weekly, monthly, and annual routines. The cards can be kept in a central catalogue and taken to the equipment as required. These again can provide an excellent source of training for new employees. A record of all routine maintenance checks should be kept in a log book.


    This is a sample page from a preventative maintenance log book. It is easy to see at a glance when equipment was last inspected.


    This fourth diagram is an example of a sample form which should be kept in all areas where there are technical equipment. They provide a simple means of reporting faults detected in equipment (people often forget to report faults). They can either be placed in a special place in each room for collection or delivered directly to the service technician. There are spaces on the form for the technician to write the necessary information that will be transferred to the maintenance history card (above).

    9. TOOL LIST

    Hand-tools

    Requirements for a Language Laboratory Maintenance Workshop

    (Basic tool requirements are indicated by a *)

        Long nose pliers Large 150 mm (heavy duty)

        Long nose pliers Small 113 mm (instrument) *

        Side cutters Large 50 mm

        Side cutters Small 105 mm *

        Multigrips Large 200 mm

        Multigrips Small 150 mm *

        Torch (Pentype) *

        Adjustable Spanner 150 mm - 300mm *

        Tin Ships Small 150 mm

        1 set Nut Drivers (including 3/16", 1/4"AF")

        1 set Hexagonal Keys (comprehensive range 1.27-3.2mm)

        1 set Wire Strippers (Optional)

        1 set of Screwdrivers from 2.6 mm to 8 mm, inc. stumpy *

        1 set if Phillips (star) Screwdrivers 2.6mm to 6mm inc. stumpy *

        1 set of Jeweler’s Screwdrivers 1.4 mm to 2.9 mm *

        1 set of 3" Instrument Files

        1 Crimping set, lugs, clips insulators and tool

        1 Junior Hacksaw *

        1 Regular Hacksaw

        1 Stanley knife *

        1 Small Wood saw set

        1 Bottle of light Machine Oil *

        1 Soldering Iron *

        Insulation tape *

        Solderwick various sizes (for de-soldering)

        Camel Hair Brush

        Paint Brush 1/4", 1/2" *

        Plastic spaghetti tubing (insulation) - various sizes

        Dentists Mirror

        Solder (resin core) 0.7 mm & 1.5mm *

        Tweezers - pointed *

        - spade nosed

        1 set Alignment tools – nylon

        Soft Eraser (rubber)*

        Araldyte

        Plastifix (plastic glue)

        1 Tool box for hand tools - may be leather case *

    Tools - Installation

        Electric Drill 3/8" chuck

        Light duty drill press for the above drill

        Kit of drills - set 1/6" to 3/8"

        Wood power bit set 3/8" to 1"

        Hole Saw set 1" to 2 1/2"

        Masonry drill set 1/8". 3/16", 1/4", 5/16", 3/8"

        Pop Riveter & Rivets

        Tapered Reamer 3.5 mm - 19 mm

        Adjustable Square

        1 set Files including a wood rasp

        1 Small Claw Hammer

        1 Pair Safety Goggles for use with the drill

    Cleaning Fluids

        Alcohol

        Isopropyl alcohol

        Spray contact cleaner

        Lens cleaning solution and tissues or cloth

        Video head spray

    Advanced Test Equipment

        Alignment and Test Tapes

        Multimeter

        Oscilloscope

        Power Supply 0-50V

        Audio Oscillator

        Clip Leads (alligator type)

        Adapters (two of each variety) RCA-Phono-BNC

        Double adapters

    Practical Tool Case

    For servicing equipment in language laboratories and general science laboratories a very suitable low cost tool case can be constructed from local materials by the laboratory technician (no special skills are required). You can construct a tool case using a cheap or second-hand briefcase. The tools are mounted on pieces of 3ply timber-laminate by elastic that is fixed in place with small rivets. You can usually fit three tool panels into one briefcase. This type of tool case can prove to be a better and a cheaper alternative to many of the commercially produced toolboxes and improves the workplace efficiency significantly because tools are more visible and easier to select. Also, you can carry technical information in the pockets inside the briefcase.

    The photo below shows a metal tool box (complete with the basic servicing tools).

    The following option is included for the benefit of any technician who may wish to experiment with alternatives to purchasing a demagnetizer. This type of experimentation can also extend the skills and knowledge of the technician. Read the notes below carefully before attempting to build the unit.

    HOMEMADE AUDIO TAPE HEAD DEMAGNETIZER
    Courtesy of Samuel M. Goldwasser (1998)

    A perfectly serviceable tape head demagnetizer can be easily constructed using a large nail, 100 turns of insulated wire (just guessing here) and an * AC wall adapter. Grind down the end of the nail so that it is not sharp and coat it with a soft material or cover the end with electrical tape to protect the finely polished heads from scratches.

    Adjust the number of turns and input voltage for desired strength. How strong should it be? A direct comparison with a commercial unit would be best but when in close proximity to a steel surface, you should be able to feel the 120 Hz attraction but it shouldn't jump out of your hand.

    NOTES:

    1. The power supply for the demagnetizer must be a LOW VOLTAGE (6 – 12 Volts AC) – ALTERNATING CURRENT source (low voltage transformer).
    2. Test the unit on some metal (iron or steel) objects before trying it on the tape heads.
    3. If you use a transformer make sure that it is safely enclosed in a box and well insulated.

    Phillip Rekdale
    Konsultan Pendidikan & Teknologi

    (Ref: SSE Project 1999)