GETTING STARTED - UNPACKING THE BOX

Your Eldorado was shipped with these parts:

1 Upper Pole Assembly

1 Middle Pole Assembly With Pole Lock

1 ABS Lower Pole Assembly

1 9 x 8 Concentric Searchcoil With 3’ Cable

1 9 Volt Alkaline Battery

1 Operator Instruction Manual

1 Tesoro Warranty Card

If any of these items are missing, contact the Tesoro Authorized Dealer where you purchased your detector immediately.

Assembly of the Eldorado is simple and requires no special tools. Just install the battery, mount the searchcoil on the lower pole assembly, connect the pole assemblies together, wrap the excess cable around the pole and plug the cable into the control housing. Finally, adjust the pole length and searchcoil angle and you're ready!

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INSTALLING THE BATTERY

Your Eldorado is equipped with a battery test switch so that you can always be sure you are getting top performance. (See QUICKSTART for operation.) The battery should be checked after the detector has been on for about 10 minutes and then periodically when used for long durations.

To install or replace the battery, first make sure the SENSITIVITY control is set to POWER OFF—turned completely counterclockwise past the “click.” Remove the battery door from the back of the control housing. Do this by pressing your thumb firmly on the louvered square—at the bottom of the battery door—and sliding the battery door upward in the direction of the arrow.

Check the polarity on the battery and on the diagram inside the battery compartment. Make sure that they match and simply drop a fresh 9 volt alkaline battery into the compartment. Note: If the battery is not installed properly, damage may occur to your detector.

Replace the battery door by sliding it into place making sure the upper mount slots are in line and the lock tongue is snapped in place.

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ASSEMBLING YOUR DETECTOR

1) On the lower pole assembly, remove the mounting screw and thumb nut from the pole tip.

2) Insert the pole tip between the mounting ears of the searchcoil and align the holes of the pole tip and washers with those of the mounting ears.

Note: The pole tip should fit very snugly into the mounting ears.

3) Insert the mounting screw through the holes in the mounting ears and pole tip—entering from the side opposite the cable connection.

4) Install the thumb nut on the mounting screw and tighten by hand.

Note: Do not overtighten the thumb nut. It should be snug but not too difficult to loosen up.

5) On the middle pole assembly, depress the two spring buttons and slide the middle pole assembly into the upper pole assembly until the spring buttons click into the holes, thus locking the two assemblies into place. Tighten the pole lock to secure the two assemblies together.

6) Slide lower pole into middle pole until spring buttons click into the first set of adjustment holes. Turn pole lock to tighten, thus locking the assembly into place.

7) Wrap the cable around the pole leaving enough slack near the searchcoil to permit searchcoil adjustment.

Note: Do not allow the cable to flop loosely over the searchcoil. Since the detector is sensitive enough to “see” the tiny wires in the cable, a floppy cable can cause false signals as the searchcoil senses the moving wires.

8) Plug the male cable end into the female connector on the control housing and tighten the cable thumb nut. You are finished!

Note: You will want to adjust the pole length and the searchcoil angle to your preference.

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ADJUSTING THE POLE & SEARCHCOIL

The pole length should be adjusted so that the detector does not become uncomfortable or tiring after long periods of use. The detector grip should rest in your hand with your arm relaxed, your elbow straight but not locked, with the pole extending out in front of you at the approximate angle shown in the photo.

You should be able to swing the detector back and forth in front of you—using relaxed shoulder movement—while keeping the searchcoil as close to the ground as possible. This swinging movement is often called a “sweep.”

The searchcoil should not touch the ground during your sweep. The pole length should be adjusted to allow this without having to lift the detector with your elbow or shoulder. The searchcoil should rest about one inch above the ground while you are standing erect. The angle of the searchcoil should allow the bottom to be parallel to the ground.

The pole length is adjusted by loosening the pole lock, then depressing the spring buttons and extending or shortening the pole until the spring buttons click into the set of holes that give you the most comfortable pole length. To adjust the searchcoil angle, simply loosen the searchcoil thumb nut slightly and move the searchcoil into the desired position. Tighten the searchcoil thumb nut by hand so that the searchcoil will hold in place.

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QUICKSTART SELF-GUIDED TUTORIAL

The Quickstart is designed to teach you how to use your new Eldorado. It provides a quick and easy means of learning your detector and the concepts behind all of the functions.

You will need the following items:

Here’s what you will do:

Prepare for the Quickstart

Place your assembled Eldorado on the nonmetal surface. Make sure that there are no metal objects near the coil and remove any jewelry from your hands and wrists.

Start with the controls as shown in the photo below:

 

Perform Audio Battery Test

Turn the SENSITIVITY knob from OFF to about 7 or 8. You will hear a quick double beep tone. This is the detector letting you know that it is turned on and ready to go. Push the MODE Switch to the left and release. The switch is spring loaded and will pop back into the center position.

If the battery is fully charged, you will hear 6 or 7 beeps. When you hear only 1 or 2 beeps, it will be time to replace your battery. This test can be performed at any time while the detector is turned on.

Adjust Threshold

To adjust the threshold tone, turn the THRESHOLD knob clockwise until you hear a slight but steady tone. You will have to turn the knob to somewhere between the 1 o’clock and 3 o’clock position to get the best hum.

The purpose of the threshold tone is to give a reference to judge targets for pinpointing and to adjust the ground balance. (For more information on ground balancing see the "Adjust GROUND BALANCE for Air Test" section below and the "Ground Balancing in the Field" section.)

In the field, some targets may be small enough or deep enough that they will not be able to generate an audio signal by themselves. By monitoring a threshold tone, you already have a threshold tone so changes are easier to hear. However, if the threshold is set too soft or too loud, small changes in the signal will be hard to hear. Take some time and find a threshold level that is right for you.

Adjust GROUND BALANCE for Air Test

The ground balance function for your Eldorado is a form of discrimination that allows you to tune out the mineralization in the ground that may mask targets or decrease the detector's depth and sensitivity. The GROUND BALANCE knob is on a 3 and ¾ turn potentiometer. While the knob will turn endlessly in either direction, when the knob is at the end of its range, a slight drag will be felt while turning.

The following procedure is for the Air Test only. For directions on ground balancing your Eldorado in the field see the "Ground Balancing in the Field" section.

To set the GROUND BALANCE knob for the Air Test, turn the knob 5 turns counterclockwise and then turn the knob 2 turns clockwise. This will make sure the GROUND BALANCE knob is just slightly above the middle part of its range. No further turns will be needed for the Air Test.

Perform Air Test in ALL METAL Mode

Once you have set the correct threshold hum and adjusted the ground balance, you are ready to perform an Air Test in the ALL METAL Mode. Your Eldorado has a VCO-style ALL METAL Mode. You will find that as targets get closer to the coil, the threshold tone will get louder and higher in pitch.

Try waving your targets in front of the coil. Start from a distance of 10 to 12 inches away from the coil and slowly work your way closer to the coil. Then try starting from 6 inches away from the left or right of your coil and work your way to the center of the coil. Notice the changes of the audio signal. Your strongest signal will always be closest to the center of the coil. Additional information can also be learned by the signal strength and pitch. A smaller or deeper target will give a less noticeable change in the threshold than a larger or more shallow target will give. Take some time and try all of your targets at different depths to find out how your detector sounds.

 

Adjust SENSITIVITY

We are now ready to switch the detector into the discriminate mode (DISC MODE). Go to the MODE switch and flip all the way to the right and into the DISC MODE setting. The switch will lock into position and you will notice that the threshold hum will stop. The discriminate circuit uses a silent search mode, meaning that no sound will be heard until the coil goes over a target. The most common use of the detector is to hunt in the DISC MODE and switch to ALL METAL to pinpoint a target. This will give you the advantage of ignoring unwanted targets and not having to listen to the threshold hum until you are ready to pinpoint and dig a target.

The all metal circuit uses a single channel to detect various metals. The discriminate circuit uses two different channels, then amplifies and filters them. The detector will then compare the signals and determine whether or not to beep at the target. While there is a great advantage to ignoring unwanted targets, it can make the circuitry more susceptible to interference. A number of outside conditions such as power lines, highly mineralized soil, and wet salt sand can cause interference.

The SENSITIVITY knob is used to raise or lower the power to the operational amplifiers, which changes the gain. Gain is a measurement of how much a signal is amplified. The higher the gain the more depth and sensitivity to small objects a detector has. Unfortunately, any small interference that is amplified can cause the detector to become erratic. The SENSITIVITY control is used to find the best gain setting in any location without letting the detector become unstable.

The SENSITIVITY knob is numbered from MIN to 10 and then has an orange area called the Max Boost Zone. For normal hunting, anywhere in the numbered zone will work very well. However, the Max Boost will allow you to increase the power to the operational amplifiers to the point of overload. This may cause your detector to become unstable and force you to turn the SENSITIVITY knob to a lower setting. An overload situation will not hurt your detector, but it will maximize the gain that is used by your detector. This can, in certain conditions such as low mineralization in the soil, cause your detector to penetrate deeper into the ground and become more sensitive to small targets.

Take some time to try waving targets in front of the coil with different sensitivity settings. Notice that the higher the sensitivity setting, the farther away from the coil that a target can be and still respond with an audio signal.

Perform Air Test in DISC Mode

As discussed before, the discriminate mode is used to filter unwanted targets from good targets. The principle behind this is pretty simple. The detector sends out a signal and then receives it back creating a small electronic field. As metal passes through the field that the detector generates, it causes a change in the received signal. The amount of change that each type of metal causes is fairly constant; therefore, we can tune our detectors to miss targets that we don’t want to find. The change is based on the type of conductivity that each target has. The general list of conductive targets is as follows: iron, foil, nickels, gold jewelry, pull tabs, screw tabs, pennies and silver coins starting with dimes and working up to silver dollars. This list is meant to be a guide only.

There is a point that some pull tabs, nickels and gold jewelry overlap. Also the depth of the target and its orientation in the ground can change the received signal. A coin that is flat to the coil will produce a better signal than a coin that is on edge. Take some time to try different combinations of depths and orientation of your targets and find out how your detector responds.

We are now ready to discriminate targets from each other. We will start with the DISCRIMINATE LEVEL at MIN. Please notice that the DISCRIMINATE LEVEL knob has words that correspond to the items that are discriminated out. There is also an arrow between IRON and 5¢. This is the recommended setting to knock out iron but still keep nickels and gold jewelry.

All four targets (the iron, nickel, pull tabs and quarter) will respond with a good audio signal at the MIN setting. Next, we will turn the DISCRIMINATE LEVEL up to the preset arrow. This should be high enough to knock out the iron target and still get a positive response on the nickel, pull tabs and quarter.

When you are done with the preset level, turn the DISCRIMINATE LEVEL to the 5¢ setting. This level is high enough to knock out the nickel. At this time the iron target and the nickel should give no response, while most of the pull tabs and the quarter will give a solid response. Next, turn the DISCRIMINATE LEVEL knob just past the PULL TAB marking. At this time most or all of the pull tabs should not give any audio signal. Only the quarter should give a strong signal. Now roll the DISCRIMINATE LEVEL all the way to MAX. Notice that the quarter is still responding. The discrimination will not go high enough to lose most of the silver coins.

This Air Test was designed to show you quickly how your discriminate mode works. Each machine may be a little different from all of the others, so you may want to take some time and try different targets to find responses of your machine. At a later date, you may want to build a test garden to test your detector in the field.

Adjust FREQ Switch

Your Eldorado comes equipped with a frequency shift switch (FREQ1, FREQ2 and FREQ3). This switch is used to change the operating frequency of your detector. This ability will help you to work a larger number of areas.

The most common use would be during a large hunt where another hunter has the same frequency machine as your detector. Two machines that are on the same frequency will start broadcasting to each other. This is called crosstalk. If you experience crosstalk in the middle of a hunt, just flip the FREQ switch to another setting. This is very easily done and can be done in the middle of a sweep. Changing the frequency can also help in some urban areas where there may be a high concentration of radio or cell phone traffic. If your detector is acting erratically after adjusting the SENSITIVITY and GROUND BALANCE, try shifting the FREQ switch and resetting the SENSITIVITY and GROUND BALANCE.

Changing the operating frequency will not change the audio frequency of the signal in the speaker. The audio frequency is controlled by a microprocessor and will not shift.

Conclusion

Congratulations, you have just finished the Quickstart for your new Eldorado detector and in the process have learned quite a lot about your detector. But experience is the best teacher. I would recommend that you get out and practice with your detector as much as possible. Any time spent using your detector will give you valuable experience.

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OPERATING TECHNIQUES

Ground Balancing In The Field

Ground balancing is not a difficult procedure, but it is critical if you desire maximum depth and stability. It is especially important if you plan to find deep relics or prospect for gold nuggets.

No matter how or where you will be hunting, or whether you will be hunting in the All Metal or Discriminate Mode, you must tune the ground balance for the area that you will be hunting. If you fail to ground balance for every site, you will not be working at the peak of your detector's performance and may lose both depth and sensitivity.

To ground balance in the field, we will start by assuming your detector is turned off. This will be the normal condition of your detector when you start hunting. Ground balancing can be done at any time while you are using the detector. It is not necessary to turn the machine off each time that you ground balance.

Start with the controls in the following position:

Turn the detector on by rolling the SENSITIVITY knob clockwise to about 9 or 10 on the dial. You will hear a quick double beep to let you know the detector is operating. Next adjust the THRESHOLD knob until a slight, steady hum is heard. The machine is now ready to be ground balanced. Next find an area that has no metal targets in the ground, as this may give false readings while in the ground balance procedure.

As shown in the photos, raise your searchcoil about 6 to 8 inches off of the ground. This is high enough so that the detector will no longer read the minerals in the ground. While listening to the threshold sound, lower the searchcoil to about 1 inch off of the ground. As the coil is dropped, the detector will start to read the ground minerals and will give you one of three sounds: 1) The threshold tone will get louder and raise in pitch. This is a positive response; 2) The threshold tone will go quiet, followed by a quick tone. This is called a negative response; 3) There will be no change in the threshold tone as the coil is dropped. This is the balanced response. When you get a balanced response, the detector is telling you that it is ready to hunt.

The positive and negative responses are easy to adjust. If you get a positive response, turn the GROUND BALANCE knob towards the minus sign on the face or in a counterclockwise direction. Getting a negative response means turning the GROUND BALANCE knob towards the plus sign on the faceplate or in a clockwise direction.

Here is an example of balancing: After setting up the detector, you raise the coil and then push it to the ground. As the coil drops, the threshold hum gets louder. You then turn the GROUND BALANCE knob counterclockwise towards the minus sign. You pick up the coil and push down again. This time you get a slight negative response. Turn the GROUND BALANCE knob a little bit towards the positive or in a clockwise direction. When raising and lowering the coil, the threshold made no change as the coil was dropped. At this point the detector is balanced for the area and is ready to hunt.

Ground balancing is a learned skill, one that you should practice often. It is easy to practice almost anywhere—your front or backyard, a local park or a fair-sized flower garden. When you are practicing, make sure that there are no pieces of metal underneath your coil that may cause a target sound. Please remember that the coil must be lifted straight off of the ground. Swinging the coil in an arc, like a pendulum, will cause false readings and will result in an improper ground balance.

 

Handling Your Detector

The detector should be held in a position that is comfortable for you as shown in the "Adjusting The Pole & Searchcoil" section in GETTING STARTED. Swing the detector from side to side in about a three foot arc, overlapping succeeding strokes well. This motion is called a “sweep.” The Eldorado 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 may even cause a loss of depth in heavily mineralized locations.

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 from the ground 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.

Pinpointing a Target

When pinpointing a target, the All Metal Mode can offer advantages over the Discriminate Mode, such as no false signals and no need to move the searchcoil to get a target response.

A good method for pinpointing in All Metal mode is “X-ing” the target with the searchcoil. Remember that the target's response sound is always greatest when the target is directly under the center of the searchcoil. To “X” a target, sweep the searchcoil over the target from side to side and then from front to back until you can identify the center of the X—the spot on the ground where the target response sound is the greatest.

Pinpointing a target in Discriminate Mode is probably best done by “X-ing” as well. Remember that the detector will beep just as the target passes under the center of the searchcoil. Slowing the sweep speed down will help you pick out the center of the X because the target response is reduced at very slow speeds making it easier to correlate the sound with the coil center.

Another easy method is to sweep the coil from side to side across the target in very short sweeps as you slowly move forward and backward across the target. Slow down the sweep rate and shorten the sweeps until you just barely get a response at one spot. The target will be directly below the coil center at this response time.

Another method of pinpointing in Discriminate Mode is to quickly change to All Metal Mode to check the target response. Remember that All Metal Mode is not susceptible to the false signals of Discriminate Mode and can sometimes give a clearer and more consistent response to difficult targets such as a dime buried next to a pull tab. By switching back and forth between modes and comparing the target response sound in All Metal to the target response sound in Discriminate, you can often better identify the likely location of the target.

Finally, raising the searchcoil during pinpointing can also help by narrowing the response to the target. Practice pinpointing often, and you will soon become more accurate and faster.

Planting a Test Garden

To better learn how your detector will perform in the field, 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 Eldorado in the All Metal & Discriminate Modes. Check the area in All Metal Mode to be sure it's clear of trash. Then bury the targets at least 1 foot apart and from 2 to 4 inches deep to start. Make a map of the area 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 speed for best operation. This type of practice area is often called a “test garden” or “test bed” and is one of the best tools to help you develop your metal detecting skills.

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RECOMMENDED RECOVERY METHODS

Adapted from "Tools 'N Techniques" By Robert H. Sickler

METHOD 1 - "PROBE AND DRIVER"

Used in less moist lawns where targets are not so deep (1 to 4 inches) and where “plugging” is objectionable. This method requires more practice but is much less damaging to grass than Method 2- “Plugging” shown in the next section.

After pinpointing the target, use a nonmetallic probe such as a modified fiberglass fishing rod or a metallic probe such as a blunted ice pick (the former causes less damage to the target) to locate the target depth (Figure 1A). Next insert an eight-inch screwdriver on center just above the target and rotate slightly to open the ground (Figure 1B). Now insert the screwdriver just under the target at an angle and lever the target to the surface (Figure 1C). Brush all loose dirt back into the hole and close the hole by exerting pressure all around the opening (Figure 1D).

 

METHOD 2 - “PLUGGING”

Used only where allowed in natural wooded areas and very moist lawn areas. Plugging in hard dry ground can damage grass roots leaving yellow “dead spots” in time.

After pinpointing the target, use a six-inch sturdy hunting knife to cut three sides of a four-inch cube around the target center (Figure 2A). Cutting a “hinged” cube-shaped plug rather than a complete cone-shaped plug will properly orient its return, prevent its removal by a lawnmower, and lessen the chance of scratching the target. With the knife blade, carefully pry against the cube side opposite the “hinge” and fold back (Figure 2B). Sweep the searchcoil over the plug and hole to isolate the target location. If the target is in the plug, carefully probe until located. If the target is in the hole and is not visible, probe the bottom and sides until located, then remove it (Figure 2C). Repeat sweep for additional targets. Replace all loose dirt with the plug. Seat the plug firmly with your foot (Figure 2D).

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GENERAL INFORMATION - CARE AND USE

Basic Care

The Eldorado is a sturdy instrument, but it is not designed to withstand abuse. In caring for your Eldorado there are several important “DO NOTs” to remember. DO NOT use it to pry rocks loose or to beat bushes out of the way. DO NOT drop the machine into water. DO NOT use it unprotected in the rain. DO NOT leave it exposed at night where dew could form on it. DO NOT store it in places that could get extremely hot (next to a woodstove, in an attic). DO NOT leave it in the trunk of a car or in the back of a hatchback-style car where high temperatures could build up. DO NOT store it with the battery installed as batteries may leak. DO NOT spray lubricants such as WD-40, or any type of cleaners, solvents, sealants or other chemicals into or onto the electronic parts, switches or controls. And finally, DO NOT attempt to modify or repair the detector’s electronics as this will void your detector's warranty.

THE WARRANTY DOES NOT COVER DAMAGE RESULTING
FROM AN ACCIDENT, NEGLECT OR ABUSE.

Protecting your investment

Often detectorists are disappointed when their new detector slowly becomes less and less responsive and seems to have lost some of its original peak performance. You can help avoid this from happening to your detector by following these basic care and protection guidelines:

• Operate your detector exactly as recommended in this Operator Instruction Manual.
• Use only high-quality alkaline batteries of the correct voltage. Never substitute a different voltage. When using a Ni-Cad battery, always use a separate convertible pack with the proper voltage output for the detector’s design.
• Remove the battery from the detector after each use. This will prevent damage to the detector if the battery leaks.
• The searchcoil cable is hard-wired to the searchcoil and protected by a strain relief. It is very important that the strain relief remains intact and should never be adjusted or tampered with.
• Keep cables properly wound around the pole stems and protect them during use. Floppy, pinched, or cables that become snagged during use may short, causing erratic noises or unnecessary replacement of the searchcoil.
• Sweep the searchcoil carefully, especially when using around rocks and building foundations. Avoid hitting the searchcoil against hard, solid objects and surfaces.
• Keep your searchcoil slightly off of the ground during the sweep, especially when using in gravel or hard, rocky dirt.
• Always use a properly designed protective scuff cover on the searchcoil. (See "Optional Accessories" in the next section.)
• Remove and clean out scuff covers periodically to avoid buildup of mineralized dirt particles which will affect performance.
• The searchcoil is waterproof and can be submerged in either fresh or salt water. After the searchcoil is used in salt water, rinse it and the lower stem assembly well with fresh water to prevent corrosion of the metal parts.
• The searchcoil is waterproof but the electronics are not, so always prevent any moisture or water from entering the control housing and never allow the cable connectors to become submerged in water.
• If working in or near water, or if there is a possibility of rain, use a protective weather resistant pouch or plastic bag to cover the control housing. Make sure it can "breathe" in order to ensure against condensation buildup inside.
• After each use, clean the detector with a soft cloth to remove dust, moisture, or other contaminants.
• When transporting the detector in a car during hot weather, store it on the floor of the passenger compartment if possible. Using a carry bag gives additional protection. In any case, never allow the detector to roll around unprotected in the trunk or back of a pickup truck.
• Protect your detector from dust, moisture, and extreme temperatures during storage.
• When shipping, use the original factory carton or similar heavy-duty container and provide a minimum one inch of padding around all parts.
• Treat your detector as you would any sensitive electronic instrument. Though ruggedly constructed and designed to withstand the demands of normal treasure hunting, proper care is essential.