Service
Inca OPERATOR INSTRUCTION MANUAL
CONGRATULATIONS!
Your new TESORO Metal Detector was designed to provide you with many happy hours of enjoyment in the most
rewarding hobby I can think of – treasure hunting. Ahead of you lie fascinating and exciting experiences as you step into the
past – uncovering artifacts lost by past generations. I wish we could share these experiences with you, and we wish you the
best of success.
Your TESORO Metal Detector is capable of meeting your needs in any conceivable treasure hunting situation. As with
any detector, operating skill and familiarity with this instrument are probably the limiting factors in determining how successful
you will be. We recommend that you read this manual and understand fully before attempting to use the instrument in the
field. As you become more familiar with your detector through practice, your rate of success will increase dramatically.
The TESORO Metal Detector is a precision electronic instrument, which will last for years if properly cared for. Treat it
right and it won't let you down.
Good Hunting! Jack Gifford
GENERAL DESCRIPTION
The Aztec is a Transmitter receiver (TR) Metal Detector, operating in the very low frequency (VLF) portion of the RF
spectrum. The detector utilizes the natural phenomena of the phase delay of all targets to provide mineral free or ground
compensated response in the normal mode of operation, or to provide discriminate capability in the discriminate mode.
The Aztec is an extremely sensitive metal detector, but because of its unique pushbutton MODE CHANGE/TUNING
SWITCH is the easiest "one handed" VLF/TR Discriminator to use.
As with any detector, the familiarity of the user with the instrument will have a great deal to do with how successful the
treasure hunter is. We recommend that you read and understand this manual fully before attempting to use the instrument in
the field.
Be sure to fill out and mail your warranty registration card to validate your warranty.
ASSEMBLY
Assembly of the Inca is very simple, and requires no special tools. The only assembly required is to mount the searchcoil
to the end of the lower stem and to install the lower stem and lock nut assembly to the upper stem.
1.
Depress the two buttons on the upper end of the lower stem, and slide it into the upper stem. Push the lower stem
up so that the buttons click into the third set of holes from the end of the upper stem.
2.
Insert the pole tip between the mounting ears of the searchcoil, after removing the screw and thumb nut. Align the
holes in the pole tip and those in the mounting ears.
3.
Insert the coil mounting screw through the coil and pole tip. The screw head should be on the side of the searchcoil
where the cable comes out.
4.
Install the thumb nut on the screw and tighten by hand.
5.
Wind the searchcoil cable around the pole by depressing the spring buttons and turning the lower stem around
several times as necessary.
ADJUSTMENT
The searchcoil angle and stem length should be adjusted so that the unit is not uncomfortable or tiring after long periods
of use. The stem length is adjusted by depressing the spring buttons and extending or shortening the pole till they click into
the holes that give you the most comfortable setting. The coil should be about one inch above the ground while standing erect.
Adjust the angle of the searchcoil, so that the coil is parallel to the ground. Tighten the searchcoil thumb nut by hand to
maintain this setting.
The arm rest on the rear of the handle can be moved forward by removing the screws and nuts, and reinstalling the
assembly into the most forward set of holes.
SPECIFICATIONS
CONTROLS
The function of the front panel controls the Inca are as follows.
1.
ON/OFF, TUNING, BATTERY TEST.
This control is used to tune the detector to it's most sensitive level (Threshold)
regardless of which mode of operation is being used. It also controls the power for the detector, and activates the
automatic battery test circuitry. The MODE control should always be in the NORMAL ONLY position and the
MODE/TUNING switch depressed when setting the unit to threshold with the TUNING control, or when checking the
batteries. The batteries should be tested after about 10 minutes of operation, and with a moderate to heavy amount of
sound. Turn the detector off momentarily, and then back on, turning the TUNING control completely clockwise to make
maximum sound. The detector will remain in the battery test mode for about 3 to 5 seconds. A meter reading of .6 or
above indicates the battery strength is adequate for proper operation. If the meter reading is below .6, replace the
batteries. Then after checking the batteries, retune to threshold before releasing the MODE/CHANGE TUNING SWITCH
and turning the MODE control switch to the desired mode of operation.
2.
GROUND ADJUST.
The control is used to adjust the detector so that it doesn't respond to the mineralization in the
ground when used in the NORMAL (all metal) mode. The GROUND ADJUST is easier to set when the MODE switch is in
the NORMAL ONLY position, since the threshold will remain when the MODE CHANGE/TUNING SWITCH is depressed
in this position.
3.
DISCRIMINATE LEVEL.
This control is used to adjust the detector's response to unwanted metallic trash when used
in the Discriminate mode. At the lowest setting "0", the detector will eliminate most iron objects, but will still respond in a
positive manner to light foil, bottle caps, pull tabs and most other metallic items. As the knob setting is increased,
response to more of these metallic trash items is reversed so that these objects give no response.
4.
DISCRIMINATE SENSITIVITY.
Since the Inca is a mineral free discriminator, this control will usually be set at the
maximum. There are situations, however, where reducing the sensitivity will yield better performance. These situations
will usually be selfevident due to spurious noise "signals" caused by very heavy metallic trash concentrations, minerals,
or RF or power line interference. Set this control as high as will allow you to operate with a tolerable level of interference.
5.
MODE SWITCH.
This switch is a three position rotary control which selects the detector's basic operating mode. In
the NORMAL ONLY mode, the pushbutton MODE CHANGE/TUNING switch acts as a TUNING switch only, and no
mode change is accomplished when the pushbutton is depressed. In the NORMAL or DISCRIM modes, depressing and
holding the pushbutton causes a change to the other mode. When the pushbutton is released, the detector returns to
the mode selected by the MODE SWITCH to help you remember which controls are operational in each of the two basic
modes.
6.
TUNING/MODE CHANGE SWITCH.
This push button switch is located in the end of the handle, where it can be
operated with the thumb of the hand holding the detector. This switch performs two functions.
A.
When depressed momentarily and released, it retunes the detector back to the desired threshold, when in NORMAL ONLY mode.
B.
When held in the depressed position, it causes the detector to switch to the other basic mode. If the MODE switch is in the Normal
position, holding the button down will cause the detector to switch to Discriminate Mode. If the MODE switch is in the Discriminate position,
holding the button down will cause the detector to switch to Normal mode. When the button is released, the detector returns to the mode
selected by the Mode switch.
7.
METER.
The meter and it's associated circuitry, while not really a control, serves two important functions.
A.
BATTERY TEST.
This function is automatically performed for about 4 seconds each time the detector power is turned on. The meter
reading will be above the .6 mark on the intensity scale when the unit is making a loud noise if the battery strength is adequate for proper
performance.
B.
COIN DEPTH.
In the NORMAL position, the meter will indicate approximate depth of the detected target, assuming the target to be coin
size. In the DISCRIM mode, the depth reading feature will be inoperable.
The coin depth reading feature of the Inca is an extremely useful aid in pinpointing. The reading will reach it's maximum forward deflection
on the meter needle when the searchcoil is directly over the target, and the meter reading will then indicate the approximate target depth.
TUNING
No detector, regardless of how powerful it is, can provide optimum depth if it is improperly tuned. In fact, the more
powerful a detector is, the more critical the tuning becomes. Less powerful units are more tolerant of operator misadjustment,
but are not capable of the depth of a properly tuned high power detector such as the Inca.
To achieve maximum performance from your Inca be sure to properly adjust the GROUND ADJUST and TUNING controls
in the Normal Mode only. The settings of these controls will also affect the detector's performance in the Discrim mode, so be
sure to adjust them properly, even if you only plan to operate the detector in the Discrim mode.
Following the tuning procedures outlined below will help you properly tune your Inca, and will allow you to fully utilize its
performance capabilities.
A. NORMAL MODE TUNING.Normal Mode Tuning.
1.
Set the Mode Switch to the Normal Only position.
2.
Depress the handle mounted pushbutton switch, and turn the On/Off Tuning control completely clockwise. Check to
see that the battery reading is above .6.
3.
After the battery test period ahs elapsed, turn the Tuning control down so the detector is making just a moderate
buzz. Be sure to keep the pushbutton depressed while setting the Tuning control.
4.
Hold the searchcoil about two feet above the ground, and release the pushbutton.
5.
Lower the searchcoil to about one or two inches above the ground, and notice any changes in the audio sound as
this is done.
6.
If the audio sound level increased, turn the Ground Adjust control slightly lower. Note that turning the Ground Adjust
control will cause a change in the audio level. Ignore this change, as it is of no consequence. The only change of concern
is that change which occurs as the searchcoil is lowered to the ground.
7.
Raise the searchcoil to about two feet above the ground, and momentarily depress the pushbutton to retune the
detector to the moderate buzz.
8.
Repeat steps 5, 6, and 7, until there is almost no change in the audio level as the searchcoil is lowered to the
ground. NOTE: the ground must be free of all metallic items where the coil is lowered. If you cannot adjust the detector to
do this, you may be over a piece of metal. Move to another spot and try again.
9.
Momentarily depress the tuning switch, and turn the TUNING control down to get just a faint audio buzz. The
detector is now ready to use in the NORMAL mode of operation. Once the detector is Ground Compensated, remember
the number setting on the GROUND ADJUST control, and use it as a starting point next time.
B. DISCRIMINATE MODE TUNING.
Tuning the Inca for use in the Discriminate mode requires that the Normal Mode tuning procedure be properly
accomplished, as the Ground Adjust control provides for mineral free operating in both the All Metal and Discrim modes. Also,
the threshold setting of the Tuning control determines the minimum sound level for deep targets in the Discriminate mode. Too
little threshold, and depth will be lost. Too much threshold, and the detector may become erratic.
After the Normal mode procedure is accomplished, the only settings necessary for operation in Discriminate mode is to
set the Disc Level control to the desired amount of trash rejection, and to set the Sensitivity control the maximum setting that
will allow smooth operation.
SELECTING THE PROPER MODE OF OPERATION
The Inca offers two basic modes of operation, the Normal mode (All Metal) and the Discriminate mode. Both modes are
mineral free if the unit is properly adjusted. The Normal mode is the industry standard "VLF" type which does not require
motion of the searchcoil for proper operation. This mode, while requiring an initial ground adjust setting of sound threshold,
offers two very important advantages, these being the ability to pin point without motion, and to provide exact ground
canceling. The Discriminate mode is based on motion of the searchcoil, but requires very little motion, and offers the
advantage of completely silent operation. Pushbutton mode change between these two modes is also included, offering the
most versatile "one handed" operating system.
Since the threshold sound will "come and go" as the push button is used to change modes, a third operation mode was
added, this being the Normal Only mode. In this mode, the mode change feature is defeated, and the detector will retune to
threshold when the pushbutton is depressed.
The Normal Only mode is the bet mode for the initial ground adjust and threshold adjustments, since the threshold does
not go away when the button is pushed. This mode would probably e the best choice for someone who is nugget hunting or
relic hunting, and is not interested in switching to Disc.
The pushbutton mode change feature of the Inca allows the user the options of either searching in normal mode to find all
targets and switching to discriminate to check them, or to search in discriminate and switch to normal to pinpoint and
measure depth. The former method has historically been the most thorough way to search a given area, but the extra slow
sweep of the Inca tends to overcome most of the disadvantages of searching in discriminate, so most people will probably
operate in discriminate because of the silent operation.
Earlier motion discriminators that are operated with the "Threshold" sound would give the user a definite indication of
metallic trash by either nulling completely or by generating short, choppy sounds. Since the Discriminate mode operates
without threshold sound, there is no nulling to indicate that the area is extremely trashy. When searching in the Discriminate
mode, we recommend that you periodically switch to Normal mode and check the area you are searching to get an idea of
how much trash is really there. In extremely heavy trash areas, it may be desirable to switch to a smaller search coil, even
through doing so will cause a loss of depth. The smaller coil will allow you a better chance of finding coins between the close
pieces of trash.
FIELD USE
The detector should be held in a position that is comfortable for you. Swing the detector from side to side in about a three
foot arc, overlapping succeeding strokes well. This motion is called a “sweep.” The Inca was designed to get maximum depth
without the frantic pace required of earlier motion detectors, so go at a pace that is comfortable for you. In fact, trying to hunt
too fast in Discriminate may even cause a loss of depth in heavily mineralized locations.
It would be helpful to bury some coins and trash metal junk items in an area that you know is clear of other metal
objects, and then try the unit in its various modes. Check the area in All Metal Mode first to be sure its clear of trash then
bury the targets at least a foot apart, and from 2 to 6 inches deep to start. Make a map of the test bed to be sure you know
what each target is and how deep it is. Practice on these targets to familiarize yourself with your detector’s target response.
This will also help you learn the proper sweep rate for DISC operation.
In Normal mode operation, keep the detector tuned so that there is just a slight buzzing of a sound. This is easy to do
because the ground minerals do not affect the Normal mode if properly adjusted. Regardless of which mode you are using, try
to keep your searchcoil height constant and close to the ground. Most people tend to raise the coil at the end of a sweep,
much like a pendulum, especially if they are hurrying. Try to avoid this, as any increase in height will cause a corresponding
loss of depth.
In areas with well kept lawns, the easiest way to maintain a constant searchcoil height is to allow the coil to rest on the
grass as you sweep from side to side. In rough and rocky areas it is best not to “scrub” the coil on the ground, as the rocks
will act like abrasives, and wear away the coil bottom (an optional coil scuff cover will protect against this.) Sweep the coil as
close to the ground as possible without touching. Hitting the ground or rocks may cause a false signal much like a desired
target would. Sweeping the coil too high above the ground results in a loss of depth.
When operating in the Discriminate Mode, some “false signals” may be caused by 1) heavy concentrations of trash metal
objects, 2) very large trash metal objects, or 3) electrical interference. These signals will sound different than good target
signals because they are generally short, choppy sounds. At the end of your sweep, as you the reverse the coil direction, the
detector is most susceptible to trash induced noise. There are two ways to tell whether these sounds are good deep signals
or trash “noise.” The first is by repeatability. Trash induced noises will not be regular as you sweep the coil over the suspected
target several times, whereas a good target response will be repeatable. The second method is to switch to All Metal Mode
and check the target response sound. If the response is weak, it may well be a deep, good target; but if the response is very
strong, it is probably trash. Note that a coin close to the surface can give a double beep sound, but it is regular and
repeatable. Raising the coil an inch or two will restore the single beep on surface targets.
If there is any doubt whether a target is good or not, DIG IT. For this same reason, in the Discriminate Mode, it is best
not to use a higher DISC LEVEL setting than necessary. Nickels and most smaller rings are rejected when the DISC LEVEL
is set to reject pull tabs on any metal detector that is a TR Discriminator like the Inca. If you don’t dig any junk at all, you are
surely passing up a lot of good finds as well. Set the DISC LEVEL only high enough to suit the conditions where you are
searching.
The sweep speed of the Inca is slow enough to allow pin pointing in the Discriminate Mode, but will require a little more
practice. Move the coil slowly from side to side and then from front to back over the target. Raising the coil slightly and
slowing the sweep speed will narrow down the detection area enough that it's easy to tell where the coil center is at the
instant of the sound.
To pinpoint in Normal mode does not require any motion, so may be easier for most people. To pin point a target that
doesn't saturate the audio, just move the coil forward and back, and side to side until you get the strongest sound. The target
will be directly below the coil center. If the audio saturates over a large area, simply push the tuning mode switch to the retune
position momentarily over the area to detune the detector. This will narrow its field of response to allow you to once again
seek the area of strongest response. It may be necessary to retune more than once with this technique. The coin depth meter
is also a good pinpointing tool, since it doesn't saturate under normal conditions. Simply switch to Normal to the side of the
target, move the coil over the target, and move it until you get the most forward deflection of the meter. This will not only tell
you target center, but depth also if you did not tune over a target.
RECOMMENDED RECOVERY METHODS
Always obtain permission from the person in charge before hunting on private property, schoolyards, parks, churches, or
state parks. Even when relic hunting in the woods, NEER LEAVE A HOLE!, or damage anything on the property.
PROTECT YOUR HOBBY FILL ALL HOLES
BATTERY REPLACEMENT
The Inca has an automatic battery test circuit so you can always know you're getting top performance from your detector.
The batteries should be tested after the detector has been operated for about ten minutes, and while the detector is making a
loud noise, so the batteries are properly loaded. To check the batteries, simply turn the Inca of for about five seconds, and
then turn it back on and rotate the TUNING control completely clockwise. Depress the TUNING/MODE CHANGE button if it is
not making lots of sound. The meter will indicate the battery strength for about four seconds. If the meter reads less than .6
during this period, replace the batteries.
To replace the batteries, pull the large knob on the battery door on the front of the unit. The entire door will pop out.
Remove the battery pack from the detector, and then remove the batteries from the pack. Replace the new penlight batteries
into the pack, observing the polarity indicators that are embossed into the insides of the pack. Slide the pack back into the
detector, making sure that the battery clip lead is connected to the pack. Install the battery door flange into the top of the
cutout in the chassis, and push the nylon fastener into the hole at the bottom of the chassis, making sure that the plungers
are still pulled out. Then push the plunger back in to lock the door in place.
Should you desire to do so, rechargeable Nickel Cadmium batteries can be substituted for standard penlight cells.
Individual AA size cells are readily available at most electronic supply stores, as well as the chargers for them, and they can
be inserted into the standard 8 holder used in your Inca. The initial battery check reading will be slightly lower, but will not
drop as much with use, until the batteries are completely discharged.
GENERAL CARE AND USE
If the detector is to be stored for a long period of time, it is best to remove the battery pack from the detector. This will
prevent internal damage to the detector if the batteries should leak.
The searchcoil is waterproof and may be submerged in either fresh or salt water. Caution should be exercised to prevent
water from entering the chassis, where it could damage the electronic circuitry. After the coil is used in salt water, the coil
and lower stem assembly should be rinsed well with fresh water to prevent corrosion of the metal parts. When used in the
body mount configuration, you should not allow the cable connectors to be submerged.
There are several good books to help the beginner learn how to use the detector, where to search and how to recover a
target without damaging the environment. A good coin shooter can recover a lot of finds and leave the area looking as though
he had never been there. Above all, always fill your holes when you have recovered the target.
TESORO Metal Detectors are sold through independent dealers, who are almost always treasure hunters themselves.
They can provide you with you much needed information about how to use your detector, how to probe, plug and dig in your
locale, and answer most of your questions about treasure hunting in general.
The use of earphones will benefit you in two ways. Most earphones will very effectively block out most of the ambient
noise, such as traffic noise and wind noise, which will enable you to better hear the fainter signals caused by the deeper
targets. Obviously, the older, more valuable coins will probably be deeper than the ones which were lost last week, so you
should take advantage of anything that will help you hear the weaker signals. Secondly, using earphones will greatly extend
the battery life, since it takes much less power to operate them. The detector is not equipped with a volume control, but does
have a limiting circuit in the earphone jack. If less volume is desired with earphones, you may want to use earphones with a
built in volume control. Any good 8 or 16 ohm set with 1/4 inch stereo jack will do.
HAPPY HUNTING, and thank you for purchasing a TESORO.
Under the copyright laws this documentation may not be copied, photocopied, reproduced, translated or reduced to any electronic or
machine readable form, in whole or in part, without the prior written consent of Tesoro Electronics Incorporated, except for the private
use of a Inca owner or operator, or in a manner otherwise described in this documentation.
© 19951996 Tesoro Electronics Incorporated. All rights reserved. Printed in the United States.
WARRANTY SERVICE
Your Tesoro metal detector is covered by a
Limited Lifetime Warranty
, the
terms of which are listed below. If your metal detector should require service, you
may return it to the Tesoro factory, or tone of the factory authorized service
centers. Contact the factory for the name and address of the nearest service
center.
If you have any questions, don't hesitate to contact the factory.
LIMITED LIFETIME WARRANTY
This warranty gives you specific legal rights, and you may have other rights
which vary from state to state.
This instrument is warranted to be free of defects in material and workmanship
as long as it is owned by the original consumer purchaser. This warranty is not
transferable, and is valid only if the warranty registration card has been completed
and mailed within 10 days of purchase.
During the first two years, TESORO will, at its option, repair or replace any
instrument covered by this warranty, without charge, except for transportation
charges, at its factory in Prescott, Arizona, or at one of its authorized repair
centers. After two years from date of purchase, TESORO will replace defective
parts at no charge except a nominal labor change and transportation charges.
This warranty excludes batteries, damage caused by leaky batteries, cable
breakage due to flexing on body mount units, and wear of the searchcoil housing.
Also excluded are instruments which have been abused, altered, or repaired by an
unauthorized party.
If warrant service should be necessary, contact the factor for nearest repair
center.
Tesoro Electronics, Inc. 715 White Spar Road Prescott, AZ, USA 86303 1928 771 2646
Operating Frequency
12 kHz
Searchcoil Type
Concentric
Searchcoil Size
8 1/2" Diameter
Cable Length
Approx. 3’
Audio Frequency
Approx. 375 Hz
Audio Output
2 1/4" speaker
Headphone Compatibility
1/4" stereo earphone jack
Weight (may vary slightly)
3 lbs. 14 oz. nominal
Battery Requirement
12 volts DC
8 AA penlight batteries
Battery Life (typical)
15 to 30 hours
Optimum Temperature Range 30° to 100° F
Optimum Humidity
0 to 75% R.H.
Operating Modes
Normal (All Metal)
Discriminate
Home
