Assembly Instructions
Assembly Procedure
- Unpack the detector and check that the following parts are included: Instruction Manual, Warranty Card, Control Box, Main Shaft, Arm-rest, Search Coil and Cable, Lower Shaft. Keep the packing carton in case you need to repack the unit at any time in the future.
- Fill in the warranty card and post it.
Figure 1. Eldorado Mark II Assembly Diagram: Diagram illustrating the assembly of the Minelab Eldorado Mk II metal detector. It shows the main components including the arm-rest (1), main shaft (2), control box (3), cable plug (4), search coil cable (5), locking nut (7), lower shaft (8), and search coil (13).
- Slide the Lower Shaft (8) containing the Search Coil and cable into the Main Shaft (2) to a convenient length and make sure it clicks into place. Tighten the locking nut (7) by hand to make the connection firm.
- Slide the Arm-rest (1) (with support fins towards the rear) over the back of the Main Shaft (2) so that it "clicks" firmly at a convenient position. You can tighten or loosen it about the forearm by bending the fins. (An optional Velcro Armstrap can be purchased to provide extra firmness during operation).
- Attach the Control Box (3) to the Main Shaft (2) at a distance from the handle grip for you to operate the RESET switch. Ensure that the surfaces at the connection are free from grit. (Do not twist the control box when removing it - grip it firmly and pull it straight off in line with the shaft.)
- Wind the Cable (5) from the Search Coil (13) around the shaft fairly tightly (but without strain) and connect and screw the Cable plug (4) to the socket on Control Box (3). Experienced operators recommend using heavy-duty insulating tape to secure the Cable to the Shaft to prevent unnecessary movement and snagging on objects.
- Install the batteries (see the section on batteries) and you are ready to start searching.
- You should use high-quality headphones for serious searching. The loudspeaker is less sensitive and without headphones your ears are not protected from stray noises.
Control Panel and Explanation of Controls
Control Panel
Illustration of the Minelab Eldorado Mk II control panel featuring controls for Volume/On/Off, Threshold, and Ground Balance, along with a Difficult/Normal toggle switch. The panel also includes indicator lights and a speaker grille.
Explanation of Controls
VOLUME/ON/OFF CONTROL
The detector is OFF when the knob is turned completely anti-clockwise. On turning the knob, you should feel a slight resistance and hear a click, signifying that the machine is in the ON position. For best performance in the field, set the knob to maximum volume (fully clockwise).
DIFFICULT/NORMAL TOGGLE SWITCH
This toggle switch should always be set on the NORMAL position for good or clear ground. The DIFFICULT setting should be selected for "difficult" ground concentrated in ironstone or mineralisation. Selecting DIFFICULT may reduce "depth" capability.
THRESHOLD
With the volume control set fully clockwise, and the detector head held away from any metal object or the ground, turn the threshold knob until a soft buzzing sound can be heard. The control behaves like a volume control; turn it clockwise for a louder response, anti-clockwise for a softer sound. Set the control just a slight turn past the point where the tone is audible, avoiding a level that would be irritating with prolonged use.
GROUND BALANCE
The ground balance is a ten-turn control. If you raise and lower the detector head (held flat) just above the ground NOT containing metal objects and the sound level of the tone changes with your movement, the detector is out of balance and requires adjustment. Ground balance is achieved when raising or lowering the head just above the ground results in minimum variation of the sound level. Vary the control according to the Ground Balance Table. As you approach the correct setting, the audio response to raising and lowering the head becomes less pronounced, requiring finer adjustments. The head should be raised about 10cm (4") and lowered to about 2 or 3 cm (1") above the ground. Inexperienced users should raise and lower the detector head slowly to ensure correct ground balancing. An improperly ground-balanced detector will not provide optimal performance. In ground with high ironstone concentrations, a different, loud, continuous tone may be heard as the head approaches the ground, indicating highly mineralised ground. In such cases, operate by raising the head slightly or switching to the Difficult/Normal toggle switch. Experienced operators may find it easier to ground balance by continuously moving the head up and down while adjusting the control.
Ground Balance Table
| YOUR ACTION | WITH THIS ACTION TONE GETS | TURN GROUND BALANCE KNOB |
|---|---|---|
| Lower head | Louder | Anticlockwise |
| Softer | Clockwise | |
| Raise head | Louder | Clockwise |
| Softer | Anticlockwise |
HEADPHONE SOCKET
Headphones should have an impedance of 8 ohms or greater. Mono or stereo headphones may be used. When the headphone jack is inserted, the loudspeaker is disconnected. Headphones allow tuning to a lower audio level, reducing distraction from outside noises like wind, and conserve battery life as the loudspeaker draws more current.
Operating Instructions
- Check the cable and connectors for breakages or loose connections. Adjust the shaft to a comfortable length and rotate the coil angle so that it lies parallel to the surface you are going to detect.
- Check that the batteries are properly installed (see batteries section for more details).
- If using headphones (not supplied), insert them fully into the Headphone Socket on the bottom right-hand corner of the detector control box.
- Switch the Difficult/Normal toggle switch on the top left of the control panel to Normal.
- Turn the threshold knob fully anti-clockwise.
- Turn the Volume control fully clockwise.
- With the detector held waist height and the coil facing away from all metal objects, switch the On/Off Toggle Switch to the ON position.
- Place the Headphones (if used) over your ears. Then adjust the Threshold knob until a soft, comfortable audio level is obtained, one that will be pleasant to work with for a prolonged period. For best results, the audio level should be set just above the quiet tone of the Threshold setting.
- To ground balance, continually raise and lower the coil between 3 and 10 cm (1" and 4") above the ground while adjusting the Ground Balance control, to obtain a constant signal without any highs or lows. If the sound builds up on the downward stroke, turn the control knob slowly anti-clockwise. If the sound builds up on the upward stroke, then adjust the control knob slowly clockwise. Continue adjusting until the best balance is achieved.
- If detecting on "hot" or mineralised ground, first switch the toggle switch from Normal to Difficult, then ground balance as explained previously.
Battery Replacement
The Battery Replacement Procedure
- Turn the detector off.
- The battery compartment is located at the bottom of the Control Box. To remove the battery lid, press down on the end of the lid nearest the front panel and slide it out.
- Take out the two battery packs, taking care not to damage the connecting wires.
- Remove the batteries from the packs and replace them with new ones. Be certain to replace them in their correct positions. Diagrams showing polarity are on the packs. Incorrect polarity will damage the detector.
- Carefully replace the loaded battery packs and slide the lid shut until it "clicks" into place.
Diagram showing battery removal and installation: Depicts the battery compartment of the Minelab Eldorado Mk II. It shows the lid being slid open (indicated by 'PUSH' and 'SLIDE') to reveal two battery packs.
Detection Tips
The Eldorado Mk 2 will return its best performance when it is ground balanced to approximately 2.5cm (1") above the ground and kept at that search height. Swinging the coil slowly will give the operator a chance to practice maintaining constant coil height at the extremity of each swing. Variation of coil height at the end of each swing is a common problem for beginners.
It is good practice to familiarise yourself with any new brand of detector. The best way to do this is to dig up all objects detected, as this will help you become familiar with the signals that different objects give, and improve your knowledge of ground noises. With Eldorado's coil configuration, you can achieve greater coverage within a shorter span of time than with a conventional detector. The wider scan coil and the longer shaft on the Eldorado enable you to cover more ground using a comfortable two-metre swing.
After appraising a target's position, best results are gained by removing the top 3-5 cm (1-2") of soil for approximately a 14cm (6") radius of the target point and flattening out the removed soil to one side. By passing the coil over the flattened soil, your detector will signal if the object is small and contained in the top layer. It can be found more readily this way than by digging a large hole. If it is not in the flattened soil, continue to dig and follow the same procedure. Do not leave sharp edges around the hole perimeter, as the detector could give a false reading on the edges. If the object is still not located, repeat the above procedure. It is better to go slowly, otherwise the object may be lost by spreading it too far from the area being worked, or if it is a small find, you may end up burying it even deeper than it was when first detected.
When the object has been removed from the hole, lay the detector down with the coil on its side, close to the hole. Gather a handful of soil at a time and pass it across the coil. The handful containing the object will emit a clear signal. Then halve the material into two hands and pass one at a time across the coil to further eliminate waste soil. This procedure is continued until the object can be seen in the hand.
Detect again over the hole to ensure there are no other objects to be found (it wouldn't be the first time that gold nuggets have been found one under the other).
Remember, fill in all holes you have dug; they are dangerous, unsightly, and environmentally unacceptable.
(Make sure that you don't wear anything metallic below your elbow on the arm you use in the procedure described above).
Ground Noises
There is nothing more annoying than getting a signal and digging but finding nothing. This can confuse the inexperienced operator and even destroy their confidence. It will take time and practice until you can learn which signals to pay attention to or to ignore.
Typically, mineralised ground can make a detector respond with an indication that there might be an object reasonably deep beneath the surface. The sound could be rather broad and not very loud, or sometimes crisp and reasonably sharp.
Charcoal can sound loud at times and rather like a metallic object when close to the surface. Experience will teach you how to read the ground efficiently and gather understanding of the detector's response to the ground. Charcoal is usually created by farmers burning off tree stumps or by bush fires. The growth is burnt below ground level, so it is not always obvious what the sounds are until you have actually dug up the causes of the noises a few times. These burns could be broad or could run in a straight line, being quite deceptive at times!
Other noises that affect detectors are "hot" rocks. These are rocks which have very strong audio signals, similar to metallic objects. Some are strong, others are weak. Some detectors have problems tuning the strong ones out, but with the Eldorado Mk 2, you can virtually tune them right out by simply ground balancing over the rock.
Many of the nugget-bearing areas are the result of broken-down reefs containing quartz and ironstone. Experienced prospectors learn to "read the ground" and look for tell-tale signs indicating potential gold-bearing fields.
It is a fascinating and exciting hobby to learn some of the skills and apply them in your search for gold.
The modern metal detector has given today's prospector enormous advantages over the prospector of old. The ground can be rapidly scanned until a small piece of gold is found, and then a study of the area made to decide where other nuggets are likely to be located. It is then best to make a systematic search of the area as indicated by the accompanying drawings.
The prospector of old, and indeed until very recent times, had to rely on seeing gold lying on the surface of the ground, or alternatively, pan for gold in selected areas. In some parts of Australia where water is scarce, panning was not possible, and it is particularly likely there are undiscovered fields in these areas.
The main problem encountered while using metal detectors is the presence of heavy concentrations of ironstone. This is particularly the case in some of the richest known fields in Australia. It appears that gold nuggets and ironstone often go together, and in fact, many gold nuggets have ironstone embedded in them or are encased in ironstone and others show strong ironstone staining. Some of these fields have only been superficially worked because of the interference to the detector by the ironstone. Usually, only the most persistent professional is prepared to spend the time and energy necessary to learn to cope with these conditions, and then only partially.
It is in these areas that the Eldorado Mk 2 will open up many opportunities. The ease of operation means that the amateur can prospect these potentially rich fields with depth of penetration and clarity of signal never before possible.
Many thousands of square kilometres of Australia are of this type of ground, with much of it potentially gold-bearing.
Our Recommended Technique
It is important to scan an area with a broad sweep of the detector head, keeping it at a constant height above the ground (approximately 2-3 cm, depending on the ground conditions and obstacles such as rocks, pieces of wood, and leaves).
Each sweep of the head should slightly overlap the previous sweep. However, unlike most other search coils, the Eldorado Mk 2 head is sensitive across its full width, and therefore only a slight overlap is required.
As indicated in the two accompanying figures, if a nugget of gold has been found, there are likely to be others, and a thorough search of the area from two different directions is recommended. This is because ground noise can vary depending on the direction the head passes across the ground.
In one direction, ground noises may mask out the sound of a nugget, whereas in another direction, the sound may be readily discernible.
Diagrams for Recommended Technique: Two diagrams illustrating recommended scanning techniques for the Minelab Eldorado Mk II. The first shows a broad, sweeping motion of the detector head. The second depicts overlapping sweeps and searching from different directions to account for varying ground noise.
Prospecting Notes and Care
Clay Domes
A common occurrence in nugget-bearing country is soil mineralisation, commonly known as "clay domes". These are regions of rather broad sound which could come from a deep, large nugget.
The following procedure will quickly establish whether or not the sound comes from clay or a metal object. Remove about 4cm of soil in a broad 30cm diameter circle with no sharp edges. This will allow the detector head to approach the "object" by about 4cm. Now, with the head in the lowered position over the hole, attempt to ground balance the signal. If ground balance can be achieved, then this source of sound is probably clay, since it is not possible to ground balance a metal object which has been brought closer to the head.
In addition, the signal from a metal object is greatly enhanced when the object is brought even slightly closer to the head, whereas the clay, because it is not concentrated, does not produce a greatly enhanced signal even when the head can be lowered. Be careful that the edges of the shallow hole are not producing spurious signals. This technique requires practice and experience but is essential to develop a good technique to avoid digging large quantities of deep holes unnecessarily.
Searching for Gold
The modern metal detector is not able to sense the presence of fine alluvial gold. It is therefore necessary to search out areas where "coarse gold" is known to have been found, or other areas where it is likely to occur.
The term "coarse gold" refers to gold ranging in size from a grain of wheat to many grams, and in some cases hundreds of grams. Fortunately, many fields of this type occur in all mainland States of Australia. Miners in the last century were required to register the weight and size of all nuggets found, and many maps were readily available which disclosed this information. There are probably many other discovered sites, however, which were never disclosed, and undoubtedly many others which are yet to be discovered.
Proper Care of Your Detector
- Taking proper care of your detector is mostly common sense. The Eldorado Mk 2 consists of high-quality electronic circuitry which should be given considerable respect.
- At all times, avoid dropping the detector and also be very careful when swinging the coil to avoid sharp objects protruding from the ground. A skid plate is recommended (they are far cheaper to replace than a coil).
- If temperatures are very high, do not leave the detector in the hot sun longer than necessary. Covering the detector from the direct sunlight will help protect it.
- It is not advisable to use the detector in the rain unless it is a very light drizzle. The Eldorado Mk 2 is water-resistant, not waterproof.
- Should the coil be used in salt water, it must be washed with fresh water. You can use a mild detergent to clean it, then fresh water rinse, then dry with a soft cloth (always avoid subjecting the control box to excessive moisture).
- Lubricants should not be used on any part of the detector's control box, especially the electronic control knobs.
- Batteries should not be left in the device when the detector is not being used, in case the batteries leak and create a corrosion problem within the electronics compartment. If a battery leak takes place, the electronic components could corrode (this would void the warranty through user negligence).
Happy Hunting!
Prospector's Notes & Locations
This section provides general context for prospecting. For specific notes and locations, consult local prospecting resources and geological surveys.
