The Rayscope Model 27 Metal Detectors are very easy to assemble and operate.  Extra care, however, should be taken when the instruments are adjusted for use, since only by careful adjustment can they be utilized to their fullest sensitivity.

A remarkable degree of sensitivity is possible to achieve with the present day tubes and transistors, but with some other makes, the sensitivity cannot be utilized because of inferior construction.  Some instruments do not have enough stability, and others lack the rigidity which is necessary for sharp adjustment.  Particular attention has been given to the stability and rigidity of the Model 27 assuring maximum effectiveness.

Although basic operating procedure is simple, some familiarization is necessary, as with anything else, to achieve maximum results.  Therefore, we recommend that before the user takes his instruments into the field, he bury a coffee can or other similar object a foot or two deep in his yard and practice until he becomes familiar with the reaction of this instrument. It is also essential that the following instructions be read carefully.  Should there be anything which is not clear, we are anxious to help all we can and welcome your questions.

Good hunting!

J. L. Cassingham
Sales Manager




The Model 27-T utilizes ring nut connectors on the handle which connect the instrument case to the detecting head.  Plug in the sockets and tighten the ring nuts.  The end of the handle with the bend in is attached to the detecting head; the other end attaches to the instrument itself.  The plugs are keyed so that they cannot be plugged in incorrectly.  Be sure the ring nuts are screwed down tight so that there will be a rigid connection.

For the Models 27 Deluxe and 27 Standard, slide the end of the handle which has the cable coming out of the left side onto the guide on the detecting head.  Clamp in place with the fastener.  Insert plug into socket.  The other end of the handle, with the cable coming out in the bottom, slides into the end of the instrument case.  Clamp in place and insert plug.


Remember, the instruments must be adjusted for operation (tuned) at the level above the ground they are to be used.  Do not tune the instrument and then lower it, as it will then be out of tune.  If the instrument is tuned close to the ground and then raised for operation at a higher level, it must be re-turned after it is raised.

To turn on the instrument, simply plug in the headphones.  When the instrument is on, a tone will sound in the headphones, unless it already happens, by accident, to be "in tune".  This tone, sometimes called a "ground signal" is the result of normal mineralization which is present in a greater or lesser degree in all soil.  The next step is to turn the black knob on the instrument case until the tone ceases.  This silence is called a "null".  The needle on the meter will return to zero.  (The 27 Standard, of course, does not have a meter.)

Next, turn the knob slowly to the right (clockwise) until the tone is heard again in the headphones.  Then turn the knob to the left slowly until the signal again disappears.  The instrument is now ready for use.

NOTE: Sometimes there will be a slight carrier signal, or "under-tone".  This is the same as the carrier signal often heard from a radio station and is perfectly normal.

When the instrument is being used, walk slowly along, carrying the instrument as level as possible.  Avoid bouncing it up and down even slightly.  It is not easy to do this, but the operator will improve with experience.  Some slight bounce, however, is impossible to avoid, and if the instrument gives a signal with each step, the tuning adjustment knob should be "backed-off" a little bit more.  Remember, when the instrument is being tuned, it is adjusted so that it is on the verge of giving a signal.  This is the point of greatest sensitivity.


Sometimes a pocket of mineralization will give a signal much like a metal object.  This can be caused by damp salt near the surface and can usually be distinguished from metal because the meter reaction (or the signal in the headphones) is slow.  With a metal object, the reaction is usually instantaneous.


Maximum signal intensity occurs when the detecting head is directly over the object.  If the object is quite large and close to the surface, sometimes a dead spot (silence) will occur near the center.  This is caused by overloading and blocking of the signal, and is not harmful to the instrument.

The instrument can be used to explore walls.  Simply hold the detecting head a few inches from the wall and then tune as is done in operating over the ground.  An object in the wall will cause a signal just as it would as if buried in the ground.

The instruments can be operated successfully over pavement, concrete, snow, ice, soil and the signal will penetrate fresh water.  Many users like to check shallow stream beds.  When using over a stream, be sure to tune the detector after wading out in the water.  Avoid getting the instrument wet.  Some owners place a large plastic bag over the detecting head for protection.

Generally speaking, the closer the instrument is held to the ground, the better the results will be.  Obviously, there will be times when boulders and other obstructions get in the way and the instrument must be held higher.  If the ground is smooth and free of rocks and brush, the detecting head may be held an inch or two above it.

It will sometimes be noted that when an object is detected, the pitch of the tone will change.  In other words, the pitch will decrease or increase when the object is right over the object.  This is an indication that the object is not very deep.  If such a pitch change does not occur, it should then be concluded that the object is small or fairly deep, or both.


The Model 27 has both "A" and "B" batteries.  It uses to standard D cells and one Burgess Number V45, 67 volt "B" battery.  Other makes of "A" and "B" batteries which are the same size can be used.  However, the batteries with heavy metal jackets should be avoided.  The flashlight cells will give 25 to 30 hours of use, and the "B" battery will last about 100 hours.  The Deluxe model is provided with a battery test switch which will give immediate readings as to battery condition.

The Model 27-T uses an activator battery which is very long lasting and should give more than a year of average use.  It is a standard battery for transistor circuits and can be obtained at most radio and hardware stores.  We use the Burgess #D-6, but Eveready and other companies make a battery with the same voltage in the same size which can be used.  To open the battery compartment, simply remove the single screw and snap the old battery out and replace it with the new one.  The snaps are constructed in such a way that the new battery cannot be attached wrong.

Important: Old batteries often carry a falsely high reading for one or two minutes.  Therefore, the batteries should always be checked with the instrument turned on and after it has been on for about two minutes, for the most accurate readings.

Tubes and transistors rarely need replacing.  They are of the highest quality and are very stable.  The characteristics of the transistors may change slightly if the temperature changes by more than 10 or 15.  However, the circuit is designed to compensate automatically for any such change, and the only noticeable result will be a slight change in the pitch.  In other words, on a warm day, the pitch may be slightly lower than on a cooler day.

If, after changing the batteries the instrument does not operate properly, it may need servicing at the factory.  Since few radio stores are equipped to service such highly specialized circuits as those used in metal detectors, it is best to pack the instrument carefully and return it by insured parcel post to the factory*.  Radio technicians can, of course, test the tubes and perform other routine checks.

If factory service is necessary, be sure to put a note with the instrument authorizing repairs.  Repairs will be done free of charge for a period up to one year after purchase, unless the defect is due to rough handling by the user.  Batteries are not, however, covered by the guarantee unless there is an obvious defect.

When the guarantee has expired, there will be a charge for service, plus a charge for any parts which may be needed.  However, parts which prove to be defective even after a year will be replaced free under the LIFETIME GUARANTEE*.


Your instrument will give you many years of service at very low maintenance cost if you will take reasonable care of it.  Always turn it off by removing the phone plug when you are through using it.  If you put it aside for 3 or 4 months or more, remove the batteries.  REMEMBER, DEAD BATTERIES CAN LEAK ACID, CAUSING DAMAGE.  We have done everything we can to give you the best possible instrument, and hope you will receive the best possible results.  If you do not understand any part of these instructions, ask for assistance.

*Reprinted from the original 1960s instruction manual.  The Rayscope Company has long ceased to exist.  This document is provided for historical reference only. No warranty or other guarantee is given or implied.